IP Prefix Advertisement in EVPN
draft-ietf-bess-evpn-prefix-advertisement-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9136.
|
|
|---|---|---|---|
| Authors | Jorge Rabadan , Wim Henderickx , John Drake , Wen Lin , Ali Sajassi | ||
| Last updated | 2017-02-13 (Latest revision 2017-02-12) | ||
| Replaces | draft-rabadan-l2vpn-evpn-prefix-advertisement | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Last Call review
(of
-10)
by Elwyn Davies
Almost ready
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Zhaohui (Jeffrey) Zhang | ||
| IESG | IESG state | Became RFC 9136 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | "Zhaohui Zhang" <zzhang@juniper.net> |
draft-ietf-bess-evpn-prefix-advertisement-04
BESS Workgroup J. Rabadan, Ed.
Internet Draft W. Henderickx
Intended status: Standards Track Nokia
J. Drake
W. Lin
Juniper
A. Sajassi
Cisco
Expires: August 17, 2017 February 13, 2017
IP Prefix Advertisement in EVPN
draft-ietf-bess-evpn-prefix-advertisement-04
Abstract
EVPN provides a flexible control plane that allows intra-subnet
connectivity in an IP/MPLS and/or an NVO-based network. In NVO
networks, there is also a need for a dynamic and efficient inter-
subnet connectivity across Tenant Systems and End Devices that can be
physical or virtual and may not support their own routing protocols.
This document defines a new EVPN route type for the advertisement of
IP Prefixes and explains some use-case examples where this new route-
type is used.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on August 17, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction and problem statement . . . . . . . . . . . . . . 3
2.1 Inter-subnet connectivity requirements in Data Centers . . . 4
2.2 The requirement for a new EVPN route type . . . . . . . . . 6
3. The BGP EVPN IP Prefix route . . . . . . . . . . . . . . . . . 8
3.1 IP Prefix Route encoding . . . . . . . . . . . . . . . . . . 8
4. Benefits of using the EVPN IP Prefix route . . . . . . . . . . 10
5. IP Prefix overlay index use-cases . . . . . . . . . . . . . . . 11
5.1 TS IP address overlay index use-case . . . . . . . . . . . . 11
5.2 Floating IP overlay index use-case . . . . . . . . . . . . . 14
5.3 ESI overlay index ("Bump in the wire") use-case . . . . . . 15
5.4 IP-VRF-to-IP-VRF model . . . . . . . . . . . . . . . . . . . 18
5.4.1 Interface-less IP-VRF-to-IP-VRF model . . . . . . . . . 19
5.4.2 Interface-full IP-VRF-to-IP-VRF with core-facing IRB . . 22
5.4.3 Interface-full IP-VRF-to-IP-VRF with unnumbered
core-facing IRB . . . . . . . . . . . . . . . . . . . . 24
6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7. Conventions used in this document . . . . . . . . . . . . . . . 28
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 28
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 28
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
10.1 Normative References . . . . . . . . . . . . . . . . . . . 29
10.2 Informative References . . . . . . . . . . . . . . . . . . 29
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 29
13. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 29
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1. Terminology
GW IP: Gateway IP Address
IPL: IP address length
IRB: Integrated Routing and Bridging interface
ML: MAC address length
NVE: Network Virtualization Edge
TS: Tenant System
VA: Virtual Appliance
RT-2: EVPN route type 2, i.e. MAC/IP advertisement route
RT-5: EVPN route type 5, i.e. IP Prefix route
AC: Attachment Circuit
Overlay index: object used in the IP Prefix route, as described in
this document. It can be an IP address in the tenant space or an ESI,
and identifies a pointer yielded by the IP route lookup at the
routing context importing the route. An overlay index always needs a
recursive route resolution on the NVE receiving the IP Prefix route,
so that the NVE knows to which egress NVE it needs to forward the
packets.
Underlay next-hop: IP address sent by BGP along with any EVPN route,
i.e. BGP next-hop. It identifies the NVE sending the route and it is
used at the receiving NVE as the VXLAN destination VTEP or NVGRE
destination end-point.
Ethernet NVO tunnel: it refers to Network Virtualization Overlay
tunnels with Ethernet payload. Examples of this type of tunnels are
VXLAN or nvGRE.
IP NVO tunnel: it refers to Network Virtualization Overlay tunnels
with IP payload (no MAC header in the payload). Examples of IP NVO
tunnels are VXLAN GPE or MPLSoGRE (both with IP payload).
2. Introduction and problem statement
Inter-subnet connectivity is required for certain tenants within the
Data Center. [EVPN-INTERSUBNET] defines some fairly common inter-
subnet forwarding scenarios where TSes can exchange packets with TSes
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located in remote subnets. In order to meet this requirement,
[EVPN-INTERSUBNET] describes how MAC/IPs encoded in TS RT-2 routes
are not only used to populate MAC-VRF and overlay ARP tables, but
also IP-VRF tables with the encoded TS host routes (/32 or /128). In
some cases, EVPN may advertise IP Prefixes and therefore provide
aggregation in the IP-VRF tables, as opposed to program individual
host routes. This document complements the scenarios described in
[EVPN-INTERSUBNET] and defines how EVPN may be used to advertise IP
Prefixes.
Section 2.1 describes the inter-subnet connectivity requirements in
Data Centers. Section 2.2 explains why a new EVPN route type is
required for IP Prefix advertisements. Once the need for a new EVPN
route type is justified, sections 3, 4 and 5 will describe this route
type and how it is used in some specific use cases.
2.1 Inter-subnet connectivity requirements in Data Centers
[RFC7432] is used as the control plane for a Network Virtualization
Overlay (NVO3) solution in Data Centers (DC), where Network
Virtualization Edge (NVE) devices can be located in Hypervisors or
TORs, as described in [EVPN-OVERLAY].
If we use the term Tenant System (TS) to designate a physical or
virtual system identified by MAC and IP addresses, and connected to
an EVPN instance, the following considerations apply:
o The Tenant Systems may be Virtual Machines (VMs) that generate
traffic from their own MAC and IP.
o The Tenant Systems may be Virtual Appliance entities (VAs) that
forward traffic to/from IP addresses of different End Devices
seating behind them.
o These VAs can be firewalls, load balancers, NAT devices, other
appliances or virtual gateways with virtual routing instances.
o These VAs do not have their own routing protocols and hence
rely on the EVPN NVEs to advertise the routes on their behalf.
o In all these cases, the VA will forward traffic to the Data
Center using its own source MAC but the source IP will be the
one associated to the End Device seating behind or a
translated IP address (part of a public NAT pool) if the VA is
performing NAT.
o Note that the same IP address could exist behind two of these
TS. One example of this would be certain appliance resiliency
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mechanisms, where a virtual IP or floating IP can be owned by
one of the two VAs running the resiliency protocol (the master
VA). VRRP is one particular example of this. Another example
is multi-homed subnets, i.e. the same subnet is connected to
two VAs.
o Although these VAs provide IP connectivity to VMs and subnets
behind them, they do not always have their own IP interface
connected to the EVPN NVE, e.g. layer-2 firewalls are examples
of VAs not supporting IP interfaces.
The following figure illustrates some of the examples described
above.
NVE1
+-----------+
TS1(VM)--|(MAC-VRF10)|-----+
IP1/M1 +-----------+ | DGW1
+---------+ +-------------+
| |----|(MAC-VRF10) |
SN1---+ NVE2 | | | IRB1\ |
| +-----------+ | | | (IP-VRF)|---+
SN2---TS2(VA)--|(MAC-VRF10)|-| | +-------------+ _|_
| IP2/M2 +-----------+ | VXLAN/ | ( )
IP4---+ <-+ | nvGRE | DGW2 ( WAN )
| | | +-------------+ (___)
vIP23 (floating) | |----|(MAC-VRF10) | |
| +---------+ | IRB2\ | |
SN1---+ <-+ NVE3 | | | | (IP-VRF)|---+
| IP3/M3 +-----------+ | | | +-------------+
SN3---TS3(VA)--|(MAC-VRF10)|---+ | |
| +-----------+ | |
IP5---+ | |
| |
NVE4 | | NVE5 +--SN5
+---------------------+ | | +-----------+ |
IP6------|(MAC-VRF1) | | +-|(MAC-VRF10)|--TS4(VA)--SN6
| \ | | +-----------+ |
| (IP-VRF) |--+ ESI4 +--SN7
| / \IRB3 |
|---|(MAC-VRF2)(MAC-VRF10)|
SN4| +---------------------+
Figure 1 DC inter-subnet use-cases
Where:
NVE1, NVE2, NVE3, NVE4, NVE5, DGW1 and DGW2 share the same EVI for a
particular tenant. EVI-10 is comprised of the collection of MAC-VRF10
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instances defined in all the NVEs. All the hosts connected to EVI-10
belong to the same IP subnet. The hosts connected to EVI-10 are
listed below:
o TS1 is a VM that generates/receives traffic from/to IP1, where
IP1 belongs to the EVI-10 subnet.
o TS2 and TS3 are Virtual Appliances (VA) that generate/receive
traffic from/to the subnets and hosts seating behind them
(SN1, SN2, SN3, IP4 and IP5). Their IP addresses (IP2 and IP3)
belong to the EVI-10 subnet and they can also generate/receive
traffic. When these VAs receive packets destined to their own
MAC addresses (M2 and M3) they will route the packets to the
proper subnet or host. These VAs do not support routing
protocols to advertise the subnets connected to them and can
move to a different server and NVE when the Cloud Management
System decides to do so. These VAs may also support redundancy
mechanisms for some subnets, similar to VRRP, where a floating
IP is owned by the master VA and only the master VA forwards
traffic to a given subnet. E.g.: vIP23 in figure 1 is a
floating IP that can be owned by TS2 or TS3 depending on who
the master is. Only the master will forward traffic to SN1.
o Integrated Routing and Bridging interfaces IRB1, IRB2 and IRB3
have their own IP addresses that belong to the EVI-10 subnet
too. These IRB interfaces connect the EVI-10 subnet to Virtual
Routing and Forwarding (IP-VRF) instances that can route the
traffic to other connected subnets for the same tenant (within
the DC or at the other end of the WAN).
o TS4 is a layer-2 VA that provides connectivity to subnets SN5,
SN6 and SN7, but does not have an IP address itself in the
EVI-10. TS4 is connected to a physical port on NVE5 assigned
to Ethernet Segment Identifier 4.
All the above DC use cases require inter-subnet forwarding and
therefore the individual host routes and subnets:
a) MUST be advertised from the NVEs (since VAs and VMs do not run
routing protocols) and
b) MAY be associated to an overlay index that can be a VA IP address,
a floating IP address or an ESI.
2.2 The requirement for a new EVPN route type
[RFC7432] defines a MAC/IP route (also referred as RT-2) where a MAC
address can be advertised together with an IP address length (IPL)
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and IP address (IP). While a variable IPL might have been used to
indicate the presence of an IP prefix in a route type 2, there are
several specific use cases in which using this route type to deliver
IP Prefixes is not suitable.
One example of such use cases is the "floating IP" example described
in section 2.1. In this example we need to decouple the advertisement
of the prefixes from the advertisement of the floating IP (vIP23 in
figure 1) and MAC associated to it, otherwise the solution gets
highly inefficient and does not scale.
E.g.: if we are advertising 1k prefixes from M2 (using RT-2) and the
floating IP owner changes from M2 to M3, we would need to withdraw 1k
routes from M2 and re-advertise 1k routes from M3. However if we use
a separate route type, we can advertise the 1k routes associated to
the floating IP address (vIP23) and only one RT-2 for advertising the
ownership of the floating IP, i.e. vIP23 and M2 in the route type 2.
When the floating IP owner changes from M2 to M3, a single RT-2
withdraw/update is required to indicate the change. The remote DGW
will not change any of the 1k prefixes associated to vIP23, but will
only update the ARP resolution entry for vIP23 (now pointing at M3).
Other reasons to decouple the IP Prefix advertisement from the MAC/IP
route are listed below:
o Clean identification, operation of troubleshooting of IP
Prefixes, not subject to interpretation and independent of the
IPL and the IP value. E.g.: a default IP route 0.0.0.0/0 must
always be easily and clearly distinguished from the absence of
IP information.
o MAC address information must not be compared by BGP when
selecting two IP Prefix routes. If IP Prefixes were to be
advertised using MAC/IP routes, the MAC information would
always be present and part of the route key.
o IP Prefix routes must not be subject to MAC/IP route
procedures such as MAC mobility or aliasing. Prefixes
advertised from two different ESIs do not mean mobility; MACs
advertised from two different ESIs do mean mobility. Similarly
load balancing for IP prefixes is achieved through IP
mechanisms such as ECMP, and not through MAC route mechanisms
such as aliasing.
o NVEs that do not require processing IP Prefixes must have an
easy way to identify an update with an IP Prefix and ignore
it, rather than processing the MAC/IP route to find out only
later that it carries a Prefix that must be ignored.
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The following sections describe how EVPN is extended with a new route
type for the advertisement of IP prefixes and how this route is used
to address the current and future inter-subnet connectivity
requirements existing in the Data Center.
3. The BGP EVPN IP Prefix route
The current BGP EVPN NLRI as defined in [RFC7432] is shown below:
+-----------------------------------+
| Route Type (1 octet) |
+-----------------------------------+
| Length (1 octet) |
+-----------------------------------+
| Route Type specific (variable) |
+-----------------------------------+
Where the route type field can contain one of the following specific
values:
+ 1 - Ethernet Auto-Discovery (A-D) route
+ 2 - MAC/IP advertisement route
+ 3 - Inclusive Multicast Route
+ 4 - Ethernet Segment Route
This document defines an additional route type that will be used for
the advertisement of IP Prefixes:
+ 5 - IP Prefix Route
The support for this new route type is OPTIONAL.
Since this new route type is OPTIONAL, an implementation not
supporting it MUST ignore the route, based on the unknown route type
value.
The detailed encoding of this route and associated procedures are
described in the following sections.
3.1 IP Prefix Route encoding
An IP Prefix advertisement route NLRI consists of the following
fields:
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+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| IP Prefix Length (1 octet) |
+---------------------------------------+
| IP Prefix (4 or 16 octets) |
+---------------------------------------+
| GW IP Address (4 or 16 octets) |
+---------------------------------------+
| MPLS Label (3 octets) |
+---------------------------------------+
Where:
o RD, Ethernet Tag ID and MPLS Label fields will be used as
defined in [RFC7432] and [EVPN-OVERLAY].
o The Ethernet Segment Identifier will be a non-zero 10-byte
identifier if the ESI is used as an overlay index. It will be
zero otherwise.
o The IP Prefix Length can be set to a value between 0 and 32
(bits) for ipv4 and between 0 and 128 for ipv6.
o The IP Prefix will be a 32 or 128-bit field (ipv4 or ipv6).
o The GW IP (Gateway IP Address) will be a 32 or 128-bit field
(ipv4 or ipv6), and will encode an overlay IP index for the IP
Prefixes. The GW IP field SHOULD be zero if it is not used as
an overlay index.
o The MPLS Label field is encoded as 3 octets, where the high-
order 20 bits contain the label value. The value SHOULD be
null when the IP Prefix route is used for a recursive lookup
resolution.
o The total route length will indicate the type of prefix (ipv4
or ipv6) and the type of GW IP address (ipv4 or ipv6). Note
that the IP Prefix + the GW IP should have a length of either
64 or 256 bits, but never 160 bits (ipv4 and ipv6 mixed values
are not allowed).
The Eth-Tag ID, IP Prefix Length and IP Prefix will be part of the
route key used by BGP to compare routes. The rest of the fields will
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not be part of the route key.
The route will contain a single overlay index at most, i.e. if the
ESI field is different from zero, the GW IP field will be zero, and
vice versa. The following table shows the different inter-subnet use-
cases described in this document and the corresponding coding of the
overlay index in the route type 5 (RT-5). The IP-VRF-to-IP-VRF or IRB
forwarding on NVEs case is a special use-case, where there may be no
need for overlay index, since the actual next-hop is given by the BGP
next-hop. When an overlay index is present in the RT-5, the receiving
NVE will need to perform a recursive route resolution to find out to
which egress NVE to forward the packets.
+----------------------------+--------------------------------------+
| Use-case | Overlay Index in the RT-5 BGP update |
+----------------------------+--------------------------------------+
| TS IP address | Overlay GW IP Address |
| Floating IP address | Overlay GW IP Address |
| "Bump in the wire" | ESI |
| IP-VRF-to-IP-VRF | Overlay GW IP, MAC or N/A |
+----------------------------+--------------------------------------+
4. Benefits of using the EVPN IP Prefix route
This section clarifies the different functions accomplished by the
EVPN RT-2 and RT-5 routes, and provides a list of benefits derived
from using a separate route type for the advertisement of IP Prefixes
in EVPN.
[RFC7432] describes the content of the BGP EVPN RT-2 specific NLRI,
i.e. MAC/IP Advertisement Route, where the IP address length (IPL)
and IP address (IP) of a specific advertised MAC are encoded. The
subject of the MAC advertisement route is the MAC address (M) and MAC
address length (ML) encoded in the route. The MAC mobility and other
procedures are defined around that MAC address. The IP address
information carries the host IP address required for the ARP
resolution of the MAC according to [RFC7432] and the host route to be
programmed in the IP-VRF [EVPN-INTERSUBNET].
The BGP EVPN route type 5 defined in this document, i.e. IP Prefix
Advertisement route, decouples the advertisement of IP prefixes from
the advertisement of any MAC address related to it. This brings some
major benefits to NVO-based networks where certain inter-subnet
forwarding scenarios are required. Some of those benefits are:
a) Upon receiving a route type 2 or type 5, an egress NVE can easily
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distinguish MACs and IPs from IP Prefixes. E.g. an IP prefix with
IPL=32 being advertised from two different ingress NVEs (as RT-5)
can be identified as such and be imported in the designated
routing context as two ECMP routes, as opposed to two MACs
competing for the same IP.
b) Similarly, upon receiving a route, an ingress NVE not supporting
processing of IP Prefixes can easily ignore the update, based on
the route type.
c) A MAC route includes the ML, M, IPL and IP in the route key that
is used by BGP to compare routes, whereas for IP Prefix routes,
only IPL and IP (as well as Ethernet Tag ID) are part of the route
key. Advertised IP Prefixes are imported into the designated
routing context, where there is no MAC information associated to
IP routes. In the example illustrated in figure 1, subnet SN1
should be advertised by NVE2 and NVE3 and interpreted by DGW1 as
the same route coming from two different next-hops, regardless of
the MAC address associated to TS2 or TS3. This is easily
accomplished in the RT-5 by including only the IP information in
the route key.
d) By decoupling the MAC from the IP Prefix advertisement procedures,
we can leave the IP Prefix advertisements out of the MAC mobility
procedures defined in [RFC7432] for MACs. In addition, this allows
us to have an indirection mechanism for IP Prefixes advertised
from a MAC/IP that can move between hypervisors. E.g. if there are
1,000 prefixes seating behind TS2 (figure 1), NVE2 will advertise
all those prefixes in RT-5 routes associated to the overlay index
IP2. Should TS2 move to a different NVE, a single MAC/IP
advertisement route withdraw for the M2/IP2 route from NVE2 will
invalidate the 1,000 prefixes, as opposed to have to wait for each
individual prefix to be withdrawn. This may be easily accomplished
by using IP Prefix routes that are not tied to a MAC address, and
use a different MAC/IP route to advertise the location and
resolution of the overlay index to a MAC address.
5. IP Prefix overlay index use-cases
The IP Prefix route can use a GW IP or an ESI as an overlay index as
well as no overlay index whatsoever. This section describes some use-
cases for these index types.
5.1 TS IP address overlay index use-case
The following figure illustrates an example of inter-subnet
forwarding for subnets seating behind Virtual Appliances (on TS2 and
TS3).
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SN1---+ NVE2 DGW1
| +-----------+ +---------+ +-------------+
SN2---TS2(VA)--|(MAC-VRF10)|-| |----|(MAC-VRF10) |
| IP2/M2 +-----------+ | | | IRB1\ |
IP4---+ | | | (IP-VRF)|---+
| | +-------------+ _|_
| VXLAN/ | ( )
| nvGRE | DGW2 ( WAN )
SN1---+ NVE3 | | +-------------+ (___)
| IP3/M3 +-----------+ | |----|(MAC-VRF10) | |
SN3---TS3(VA)--|(MAC-VRF10)|-| | | IRB2\ | |
| +-----------+ +---------+ | (IP-VRF)|---+
IP5---+ +-------------+
Figure 2 TS IP address use-case
An example of inter-subnet forwarding between subnet SN1/24 and a
subnet seating in the WAN is described below. NVE2, NVE3, DGW1 and
DGW2 are running BGP EVPN. TS2 and TS3 do not support routing
protocols, only a static route to forward the traffic to the WAN.
(1) NVE2 advertises the following BGP routes on behalf of TS2:
o Route type 2 (MAC/IP route) containing: ML=48, M=M2, IPL=32,
IP=IP2 and [RFC5512] BGP Encapsulation Extended Community with
the corresponding Tunnel-type.
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
ESI=0, GW IP address=IP2.
(2) NVE3 advertises the following BGP routes on behalf of TS3:
o Route type 2 (MAC/IP route) containing: ML=48, M=M3, IPL=32,
IP=IP3 (and BGP Encapsulation Extended Community).
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
ESI=0, GW IP address=IP3.
(3) DGW1 and DGW2 import both received routes based on the
route-targets:
o Based on the MAC-VRF10 route-target in DGW1 and DGW2, the
MAC/IP route is imported and M2 is added to the MAC-VRF10
along with its corresponding tunnel information. For instance,
if VXLAN is used, the VTEP will be derived from the MAC/IP
route BGP next-hop (underlay next-hop) and VNI from the MPLS
Label1 field. IP2 - M2 is added to the ARP table.
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o Based on the MAC-VRF10 route-target in DGW1 and DGW2, the IP
Prefix route is also imported and SN1/24 is added to the IP-
VRF with overlay index IP2 pointing at the local MAC-VRF10.
Should ECMP be enabled in the IP-VRF, SN1/24 would also be
added to the routing table with overlay index IP3.
(4) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 IP-VRF
routing table and overlay index=IP2 is found. Since IP2 is an
overlay index a recursive route resolution is required for
IP2.
o IP2 is resolved to M2 in the ARP table, and M2 is resolved to
the tunnel information given by the MAC-VRF FIB (e.g. remote
VTEP and VNI for the VXLAN case).
o The IP packet destined to IPx is encapsulated with:
. Source inner MAC = IRB1 MAC.
. Destination inner MAC = M2.
. Tunnel information provided by the MAC-VRF (VNI, VTEP IPs
and MACs for the VXLAN case).
(5) When the packet arrives at NVE2:
o Based on the tunnel information (VNI for the VXLAN case), the
MAC-VRF10 context is identified for a MAC lookup.
o Encapsulation is stripped-off and based on a MAC lookup
(assuming MAC forwarding on the egress NVE), the packet is
forwarded to TS2, where it will be properly routed.
(6) Should TS2 move from NVE2 to NVE3, MAC Mobility procedures will
be applied to the MAC route IP2/M2, as defined in [RFC7432].
Route type 5 prefixes are not subject to MAC mobility procedures,
hence no changes in the DGW IP-VRF routing table will occur for
TS2 mobility, i.e. all the prefixes will still be pointing at IP2
as overlay index. There is an indirection for e.g. SN1/24, which
still points at overlay index IP2 in the routing table, but IP2
will be simply resolved to a different tunnel, based on the
outcome of the MAC mobility procedures for the MAC/IP route
IP2/M2.
Note that in the opposite direction, TS2 will send traffic based on
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its static-route next-hop information (IRB1 and/or IRB2), and regular
EVPN procedures will be applied.
5.2 Floating IP overlay index use-case
Sometimes Tenant Systems (TS) work in active/standby mode where an
upstream floating IP - owned by the active TS - is used as the
overlay index to get to some subnets behind. This redundancy mode,
already introduced in section 2.1 and 2.2, is illustrated in Figure
3.
NVE2 DGW1
+-----------+ +---------+ +-------------+
+---TS2(VA)--|(MAC-VRF10)|-| |----|(MAC-VRF10) |
| IP2/M2 +-----------+ | | | IRB1\ |
| <-+ | | | (IP-VRF)|---+
| | | | +-------------+ _|_
SN1 vIP23 (floating) | VXLAN/ | ( )
| | | nvGRE | DGW2 ( WAN )
| <-+ NVE3 | | +-------------+ (___)
| IP3/M3 +-----------+ | |----|(MAC-VRF10) | |
+---TS3(VA)--|(MAC-VRF10)|-| | | IRB2\ | |
+-----------+ +---------+ | (IP-VRF)|---+
+-------------+
Figure 3 Floating IP overlay index for redundant TS
In this example, assuming TS2 is the active TS and owns IP23:
(1) NVE2 advertises the following BGP routes for TS2:
o Route type 2 (MAC/IP route) containing: ML=48, M=M2, IPL=32,
IP=IP23 (and BGP Encapsulation Extended Community).
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
ESI=0, GW IP address=IP23.
(2) NVE3 advertises the following BGP routes for TS3:
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
ESI=0, GW IP address=IP23.
(3) DGW1 and DGW2 import both received routes based on the route-
target:
o M2 is added to the MAC-VRF10 FIB along with its corresponding
tunnel information. For the VXLAN use case, the VTEP will be
derived from the MAC/IP route BGP next-hop and VNI from the
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VNI/VSID field. IP23 - M2 is added to the ARP table.
o SN1/24 is added to the IP-VRF in DGW1 and DGW2 with overlay
index IP23 pointing at the local MAC-VRF10.
(4) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 IP-VRF
routing table and overlay index=IP23 is found. Since IP23 is
an overlay index, a recursive route resolution for IP23 is
required.
o IP23 is resolved to M2 in the ARP table, and M2 is resolved to
the tunnel information given by the MAC-VRF (remote VTEP and
VNI for the VXLAN case).
o The IP packet destined to IPx is encapsulated with:
. Source inner MAC = IRB1 MAC.
. Destination inner MAC = M2.
. Tunnel information provided by the MAC-VRF FIB (VNI, VTEP
IPs and MACs for the VXLAN case).
(5) When the packet arrives at NVE2:
o Based on the tunnel information (VNI for the VXLAN case), the
MAC-VRF10 context is identified for a MAC lookup.
o Encapsulation is stripped-off and based on a MAC lookup
(assuming MAC forwarding on the egress NVE), the packet is
forwarded to TS2, where it will be properly routed.
(6) When the redundancy protocol running between TS2 and TS3 appoints
TS3 as the new active TS for SN1, TS3 will now own the floating
IP23 and will signal this new ownership (GARP message or
similar). Upon receiving the new owner's notification, NVE3 will
issue a route type 2 for M3-IP23. DGW1 and DGW2 will update their
ARP tables with the new MAC resolving the floating IP. No changes
are carried out in the IP-VRF routing table.
5.3 ESI overlay index ("Bump in the wire") use-case
Figure 5 illustrates an example of inter-subnet forwarding for an IP
Prefix route that carries a subnet SN1 and uses an ESI as an overlay
index (ESI23). In this use-case, TS2 and TS3 are layer-2 VA devices
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without any IP address that can be included as an overlay index in
the GW IP field of the IP Prefix route. Their MAC addresses are M2
and M3 respectively and are connected to EVI-10. Note that IRB1 and
IRB2 (in DGW1 and DGW2 respectively) have IP addresses in a subnet
different than SN1.
NVE2 DGW1
M2 +-----------+ +---------+ +-------------+
+---TS2(VA)--|(MAC-VRF10)|-| |----|(MAC-VRF10) |
| ESI23 +-----------+ | | | IRB1\ |
| + | | | (IP-VRF)|---+
| | | | +-------------+ _|_
SN1 | | VXLAN/ | ( )
| | | nvGRE | DGW2 ( WAN )
| + NVE3 | | +-------------+ (___)
| ESI23 +-----------+ | |----|(MAC-VRF10) | |
+---TS3(VA)--|(MAC-VRF10)|-| | | IRB2\ | |
M3 +-----------+ +---------+ | (IP-VRF)|---+
+-------------+
Figure 5 ESI overlay index use-case
Since neither TS2 nor TS3 can run any routing protocol and have no IP
address assigned, an ESI, i.e. ESI23, will be provisioned on the
attachment ports of NVE2 and NVE3. This model supports VA redundancy
in a similar way as the one described in section 5.2 for the floating
IP overlay index use-case, only using the EVPN Ethernet A-D route
instead of the MAC advertisement route to advertise the location of
the overlay index. The procedure is explained below:
(1) NVE2 advertises the following BGP routes for TS2:
o Route type 1 (Ethernet A-D route for EVI-10) containing:
ESI=ESI23 and the corresponding tunnel information (VNI/VSID
field), as well as the BGP Encapsulation Extended Community as
per [EVPN-OVERLAY].
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
ESI=ESI23, GW IP address=0. The Router's MAC Extended
Community defined in [EVPN-INTERSUBNET] is added and carries
the MAC address (M2) associated to the TS behind which SN1
seats.
(2) NVE3 advertises the following BGP routes for TS3:
o Route type 1 (Ethernet A-D route for EVI-10) containing:
ESI=ESI23 and the corresponding tunnel information (VNI/VSID
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field), as well as the BGP Encapsulation Extended Community.
o Route type 5 (IP Prefix route) containing: IPL=24, IP=SN1,
ESI=23, GW IP address=0. The Router's MAC Extended Community
is added and carries the MAC address (M3) associated to the TS
behind which SN1 seats.
(3) DGW1 and DGW2 import the received routes based on the route-
target:
o The tunnel information to get to ESI23 is installed in DGW1
and DGW2. For the VXLAN use case, the VTEP will be derived
from the Ethernet A-D route BGP next-hop and VNI from the
VNI/VSID field (see [EVPN-OVERLAY]).
o SN1/24 is added to the IP-VRF in DGW1 and DGW2 with overlay
index ESI23.
(4) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 IP-VRF
routing table and overlay index=ESI23 is found. Since ESI23 is
an overlay index, a recursive route resolution is required to
find the egress NVE where ESI23 resides.
o The IP packet destined to IPx is encapsulated with:
. Source inner MAC = IRB1 MAC.
. Destination inner MAC = M2 (this MAC will be obtained
from the Router's MAC Extended Community received along
with the RT-5 for SN1).
. Tunnel information for the NVO tunnel is provided by the
Ethernet A-D route per-EVI for ESI23 (VNI and VTEP IP for
the VXLAN case).
(5) When the packet arrives at NVE2:
o Based on the tunnel demultiplexer information (VNI for the
VXLAN case), the MAC-VRF10 context is identified for a MAC
lookup (assuming MAC disposition model) or the VNI MAY
directly identify the egress interface (for a label or VNI
disposition model).
o Encapsulation is stripped-off and based on a MAC lookup
(assuming MAC forwarding on the egress NVE) or a VNI lookup
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(in case of VNI forwarding), the packet is forwarded to TS2,
where it will be forwarded to SN1.
(6) If the redundancy protocol running between TS2 and TS3 follows an
active/standby model and there is a failure, appointing TS3 as
the new active TS for SN1, TS3 will now own the connectivity to
SN1 and will signal this new ownership. Upon receiving the new
owner's notification, NVE3's AC will become active and issue a
route type 1 for ESI23, whereas NVE2 will withdraw its Ethernet
A-D route for ESI23. DGW1 and DGW2 will update their tunnel
information to resolve ESI23. The destination inner MAC will be
changed to M3.
5.4 IP-VRF-to-IP-VRF model
This use-case is similar to the scenario described in "IRB forwarding
on NVEs for Tenant Systems" in [EVPN-INTERSUBNET], however the new
requirement here is the advertisement of IP Prefixes as opposed to
only host routes.
In the examples described in sections 5.1, 5.2 and 5.3, the MAC-VRF
instance can connect IRB interfaces and any other Tenant Systems
connected to it. EVPN provides connectivity for:
1. Traffic destined to the IRB IP interfaces as well as
2. Traffic destined to IP subnets seating behind the TS, e.g. SN1 or
SN2.
In order to provide connectivity for (1), MAC/IP routes (RT-2) are
needed so that IRB MACs and IPs can be distributed. Connectivity type
(2) is accomplished by the exchange of IP Prefix routes (RT-5) for
IPs and subnets seating behind certain overlay indexes, e.g. GW IP or
ESI.
In some cases, IP Prefix routes may be advertised for subnets and IPs
seating behind an IRB. We refer to this use-case as the "IP-VRF-to-
IP-VRF" model.
[EVPN-INTERSUBNET] defines an asymmetric IRB model and a symmetric
IRB model, based on the required lookups at the ingress and egress
NVE: the asymmetric model requires an ip-lookup and a mac-lookup at
the ingress NVE, whereas only a mac-lookup is needed at the egress
NVE; the symmetric model requires ip and mac lookups at both, ingress
and egress NVE. From that perspective, the IP-VRF-to-IP-VRF use-case
described in this section is a symmetric IRB model. Note that in an
IP-VRF-to-IP-VRF scenario, a PE may not be configured with any MAC-
VRF for a given tenant, in which case it will only be doing IP
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lookups and forwarding for that tenant.
Based on the way the IP-VRFs are interconnected, there are three
different IP-VRF-to-IP-VRF scenarios identified and described in this
document:
1) Interface-less model
2) Interface-full with core-facing IRB model
3) Interface-full with unnumbered core-facing IRB model
5.4.1 Interface-less IP-VRF-to-IP-VRF model
Figure 6 will be used for the description of this model.
NVE1(M1)
+------------+
IP1+----|(MAC-VRF1) | DGW1(M3)
| \ | +---------+ +--------+
| (IP-VRF)|----| |-|(IP-VRF)|----+
| / | | | +--------+ |
+---|(MAC-VRF2) | | | _+_
| +------------+ | | ( )
SN1| | VXLAN/ | ( WAN )
| NVE2(M2) | nvGRE/ | (___)
| +------------+ | MPLS | +
+---|(MAC-VRF2) | | | DGW2(M4) |
| \ | | | +--------+ |
| (IP-VRF)|----| |-|(IP-VRF)|----+
| / | +---------+ +--------+
SN2+----|(MAC-VRF3) |
+------------+
Figure 6 Interface-less IP-VRF-to-IP-VRF model
In this case, the requirements are the following:
a) The NVEs and DGWs must provide connectivity between hosts in SN1,
SN2, IP1 and hosts seating at the other end of the WAN.
b) The IP-VRF instances in the NVE/DGWs are directly connected
through NVO tunnels, and no IRBs and/or MAC-VRF instances are
defined at the core.
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c) The solution must provide layer-3 connectivity among the IP-VRFs
for Ethernet NVO tunnels, for instance, VXLAN or nvGRE.
d) The solution may provide layer-3 connectivity among the IP-VRFs
for IP NVO tunnels, for example, VXLAN GPE (with IP payload).
In order to meet the above requirements, the EVPN route type 5 will
be used to advertise the IP Prefixes, along with the Router's MAC
Extended Community as defined in [EVPN-INTERSUBNET] if the
advertising NVE/DGW uses Ethernet NVO tunnels. Each NVE/DGW will
advertise an RT-5 for each of its prefixes with the following fields:
o RD as per [RFC7432].
o Eth-Tag ID=0 assuming VLAN-based service.
o IP address length and IP address, as explained in the previous
sections.
o GW IP address= SHOULD be set to 0.
o ESI=0
o MPLS label or VNI corresponding to the IP-VRF.
Each RT-5 will be sent with a route-target identifying the tenant
(IP-VRF) and two BGP extended communities:
o The first one is the BGP Encapsulation Extended Community, as
per [RFC5512], identifying the tunnel type.
o The second one is the Router's MAC Extended Community as per
[EVPN-INTERSUBNET] containing the MAC address associated to
the NVE advertising the route. This MAC address identifies the
NVE/DGW and MAY be re-used for all the IP-VRFs in the NVE. The
Router's MAC Extended Community MUST be sent if the route is
associated to an Ethernet NVO tunnel, for instance, VXLAN. If
the route is associated to an IP NVO tunnel, for instance
VXLAN GPE with IP payload, the Router's MAC Extended Community
SHOULD NOT be sent.
The following example illustrates the procedure to advertise and
forward packets to SN1/24 (ipv4 prefix advertised from NVE1) for
VXLAN tunnels:
(1) NVE1 advertises the following BGP route:
o Route type 5 (IP Prefix route) containing:
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. IPL=24, IP=SN1, VNI=10.
. GW IP= SHOULD be set to 0.
. [RFC5512] BGP Encapsulation Extended Community with Tunnel-
type=VXLAN.
. Router's MAC Extended Community that contains M1.
. Route-target identifying the tenant (IP-VRF).
(2) DGW1 imports the received routes from NVE1:
o DGW1 installs SN1/24 in the IP-VRF identified by the RT-5
route-target.
o Since GW IP=0 and the VNI is a valid value, DGW1 will use the
VNI and next-hop of the RT-5, as well as the MAC address
conveyed in the Router's MAC Extended Community (as inner
destination MAC address) to encapsulate the routed IP packets.
(3) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 IP-VRF
routing table. The lookup yields SN1/24.
o Since the RT-5 for SN1/24 had a GW IP=0 and a valid VNI and
next-hop (used as destination VTEP), DGW1 will not need a
recursive lookup to resolve the route.
o The IP packet destined to IPx is encapsulated with: Source
inner MAC = DGW1 MAC, Destination inner MAC = M1, Source outer
IP (source VTEP) = DGW1 IP, Destination outer IP (destination
VTEP) = NVE1 IP.
(4) When the packet arrives at NVE1:
o NVE1 will identify the IP-VRF for an IP-lookup based on the
VNI.
o An IP lookup is performed in the routing context, where SN1
turns out to be a local subnet associated to MAC-VRF2. A
subsequent lookup in the ARP table and the MAC-VRF FIB will
provide the forwarding information for the packet in MAC-VRF2.
The implementation of this Interface-less model is REQUIRED.
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5.4.2 Interface-full IP-VRF-to-IP-VRF with core-facing IRB
Figure 7 will be used for the description of this model.
NVE1
+------------+ DGW1
IP1+----+(MAC-VRF1) | +---------------+ +------------+
| \ (core) (core) |
|(IP-VRF)(MAC-VRF) (MAC-VRF)(IP-VRF)|-----+
| / IRB(IP1/M1) IRB(IP3/M3) | |
+---+(MAC-VRF2) | | | +------------+ _+_
| +------------+ | | ( )
SN1| | VXLAN/ | ( WAN )
| NVE2 | nvGRE/ | (___)
| +------------+ | MPLS | DGW2 +
+---+(MAC-VRF2) | | | +------------+ |
| \ (core) (core) | |
|(IP-VRF)(MAC-VRF) (MAC-VRF)(IP-VRF)|-----+
| / IRB(IP2/M2) IRB(IP4/M4) |
SN2+----+(MAC-VRF3) | +---------------+ +------------+
+------------+
Figure 7 Interface-full with core-facing IRB model
In this model, the requirements are the following:
a) As in section 5.4.1, the NVEs and DGWs must provide connectivity
between hosts in SN1, SN2, IP1 and hosts seating at the other end
of the WAN.
b) However, the NVE/DGWs are now connected through Ethernet NVO
tunnels terminated in core-MAC-VRF instances. The IP-VRFs use IRB
interfaces for their connectivity to the core MAC-VRFs.
c) Each core-facing IRB has an IP and a MAC address, where the IP
address must be reachable from other NVEs or DGWs.
d) The core EVI is composed of the NVE/DGW MAC-VRFs and may contain
other MAC-VRFs without IRB interfaces. Those non-IRB MAC-VRFs will
typically connect TSes that need layer-3 connectivity to remote
subnets.
e) The solution must provide layer-3 connectivity for Ethernet NVO
tunnels, for instance, VXLAN or nvGRE.
EVPN type 5 routes will be used to advertise the IP Prefixes, whereas
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EVPN RT-2 routes will advertise the MAC/IP addresses of each core-
facing IRB interface. Each NVE/DGW will advertise an RT-5 for each of
its prefixes with the following fields:
o RD as per [RFC7432].
o Eth-Tag ID=0 assuming VLAN-based service.
o IP address length and IP address, as explained in the previous
sections.
o GW IP address=IRB-IP (this is the overlay index that will be
used for the recursive route resolution).
o ESI=0
o MPLS label or VNI corresponding to the IP-VRF. Note that the
value SHOULD be zero since the RT-5 route requires a recursive
lookup resolution to an RT-2 route. The MPLS label or VNI to
be used when forwarding packets will be derived from the RT-
2's MPLS Label1 field.
Each RT-5 will be sent with a route-target identifying the tenant
(IP-VRF). The Router's MAC Extended Community SHOULD NOT be sent in
this case.
The following example illustrates the procedure to advertise and
forward packets to SN1/24 (ipv4 prefix advertised from NVE1) for
VXLAN tunnels:
(1) NVE1 advertises the following BGP routes:
o Route type 5 (IP Prefix route) containing:
. IPL=24, IP=SN1, VNI= SHOULD be set to 0.
. GW IP=IP1 (core-facing IRB's IP)
. Route-target identifying the tenant (IP-VRF).
o Route type 2 (MAC/IP route for the core-facing IRB)
containing:
. ML=48, M=M1, IPL=32, IP=IP1, VNI=10.
. A [RFC5512] BGP Encapsulation Extended Community with
Tunnel-type= VXLAN.
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. Route-target identifying the tenant. This route-target MAY
be the same as the one used with the RT-5.
(2) DGW1 imports the received routes from NVE1:
o DGW1 installs SN1/24 in the IP-VRF identified by the RT-5
route-target.
. Since GW IP is different from zero, the GW IP (IP1) will be
used as the overlay index for the recursive route resolution
to the RT-2 carrying IP1.
(3) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 IP-VRF
routing table. The lookup yields SN1/24, which is associated
to the overlay index IP1. The forwarding information is
derived from the RT-2 received for IP1.
o The IP packet destined to IPx is encapsulated with: Source
inner MAC = M3, Destination inner MAC = M1, Source outer IP
(source VTEP) = DGW1 IP, Destination outer IP (destination
VTEP) = NVE1 IP.
(4) When the packet arrives at NVE1:
o NVE1 will identify the IP-VRF for an IP-lookup based on the
VNI and the inner MAC DA.
o An IP lookup is performed in the routing context, where SN1
turns out to be a local subnet associated to MAC-VRF2. A
subsequent lookup in the ARP table and the MAC-VRF FIB will
provide the forwarding information for the packet in MAC-VRF2.
The implementation of the Interface-full with core-facing IRB model
is REQUIRED.
5.4.3 Interface-full IP-VRF-to-IP-VRF with unnumbered core-facing IRB
Figure 8 will be used for the description of this model. Note that
this model is similar to the one described in section 5.4.2, only
without IP addresses on the core-facing IRB interfaces.
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NVE1
+------------+ DGW1
IP1+----+(MAC-VRF1) | +---------------+ +------------+
| \ (core) (core) |
|(IP-VRF)(MAC-VRF) (MAC-VRF)(IP-VRF)|-----+
| / IRB(M1)| | IRB(M3) | |
+---+(MAC-VRF2) | | | +------------+ _+_
| +------------+ | | ( )
SN1| | VXLAN/ | ( WAN )
| NVE2 | nvGRE/ | (___)
| +------------+ | MPLS | DGW2 +
+---+(MAC-VRF2) | | | +------------+ |
| \ (core) (core) | |
|(IP-VRF)(MAC-VRF) (MAC-VRF)(IP-VRF)|-----+
| / IRB(M2)| | IRB(M4) |
SN2+----+(MAC-VRF3) | +---------------+ +------------+
+------------+
Figure 8 Interface-full with unnumbered core-facing IRB model
In this model, the requirements are the following:
a) As in section 5.4.1 and 5.4.2, the NVEs and DGWs must provide
connectivity between hosts in SN1, SN2, IP1 and hosts seating at
the other end of the WAN.
b) As in section 5.4.2, the NVE/DGWs are connected through Ethernet
NVO tunnels terminated in core-MAC-VRF instances. The IP-VRFs use
IRB interfaces for their connectivity to the core MAC-VRFs.
c) However, each core-facing IRB has a MAC address only, and no IP
address (that is why the model refers to an 'unnumbered' core-
facing IRB). In this model, there is no need to have IP
reachability to the core-facing IRB interfaces themselves and
there is a requirement to save IP addresses on those interfaces.
d) As in section 5.4.2, the core EVI is composed of the NVE/DGW MAC-
VRFs and may contain other MAC-VRFs.
e) As in section 5.4.2, the solution must provide layer-3
connectivity for Ethernet NVO tunnels, for instance, VXLAN or
nvGRE.
This model will also make use of the RT-5 recursive resolution. EVPN
type 5 routes will advertise the IP Prefixes along with the Router's
MAC Extended Community used for the recursive lookup, whereas EVPN
RT-2 routes will advertise the MAC addresses of each core-facing IRB
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interface (this time without an IP). Each NVE/DGW will advertise an
RT-5 for each of its prefixes with the following fields:
o RD as per [RFC7432].
o Eth-Tag ID=0 assuming VLAN-based service.
o IP address length and IP address, as explained in the previous
sections.
o GW IP address= SHOULD be set to 0.
o ESI=0
o MPLS label or VNI corresponding to the IP-VRF. Note that the
value SHOULD be zero since the RT-5 route requires a recursive
lookup resolution to an RT-2 route. The MPLS label or VNI to
be used when forwarding packets will be derived from the RT-
2's MPLS Label1 field.
Each RT-5 will be sent with a route-target identifying the tenant
(IP-VRF) and the Router's MAC Extended Community containing the MAC
address associated to core-facing IRB interface. This MAC address MAY
be re-used for all the IP-VRFs in the NVE.
The following example illustrates the procedure to advertise and
forward packets to SN1/24 (ipv4 prefix advertised from NVE1) for
VXLAN tunnels:
(1) NVE1 advertises the following BGP routes:
o Route type 5 (IP Prefix route) containing:
. IPL=24, IP=SN1, VNI= SHOULD be set to 0.
. GW IP= SHOULD be set to 0.
. Router's MAC Extended Community containing M1 (this will be
used for the recursive lookup to a RT-2).
. Route-target identifying the tenant (IP-VRF).
o Route type 2 (MAC route for the core-facing IRB) containing:
. ML=48, M=M1, IPL=0, VNI=10.
. A [RFC5512] BGP Encapsulation Extended Community with
Tunnel-type=VXLAN.
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. Route-target identifying the tenant. This route-target MAY
be the same as the one used with the RT-5.
(2) DGW1 imports the received routes from NVE1:
o DGW1 installs SN1/24 in the IP-VRF identified by the RT-5
route-target.
. The MAC contained in the Router's MAC Extended Community
sent along with the RT-5 (M1) will be used as the overlay
index for the recursive route resolution to the RT-2
carrying M1.
(3) When DGW1 receives a packet from the WAN with destination IPx,
where IPx belongs to SN1/24:
o A destination IP lookup is performed on the DGW1 IP-VRF
routing table. The lookup yields SN1/24, which is associated
to the overlay index M1. The forwarding information is derived
from the RT-2 received for M1.
o The IP packet destined to IPx is encapsulated with: Source
inner MAC = M3, Destination inner MAC = M1, Source outer IP
(source VTEP) = DGW1 IP, Destination outer IP (destination
VTEP) = NVE1 IP.
(4) When the packet arrives at NVE1:
o NVE1 will identify the IP-VRF for an IP-lookup based on the
VNI and the inner MAC DA.
o An IP lookup is performed in the routing context, where SN1
turns out to be a local subnet associated to MAC-VRF2. A
subsequent lookup in the ARP table and the MAC-VRF FIB will
provide the forwarding information for the packet in MAC-VRF2.
The implementation of the Interface-full with unnumbered core-facing
IRB model is OPTIONAL.
6. Conclusions
An EVPN route (type 5) for the advertisement of IP Prefixes is
described in this document. This new route type has a differentiated
role from the RT-2 route and addresses all the Data Center (or NVO-
based networks in general) inter-subnet connectivity scenarios in
which an IP Prefix advertisement is required. Using this new RT-5, an
IP Prefix may be advertised along with an overlay index that can be a
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GW IP address, a MAC or an ESI, or without an overlay index, in which
case the BGP next-hop will point at the egress NVE and the MAC in the
Router's MAC Extended Community will provide the inner MAC
destination address to be used. As discussed throughout the document,
the EVPN RT-2 does not meet the requirements for all the DC use
cases, therefore this EVPN route type 5 is required.
The EVPN route type 5 decouples the IP Prefix advertisements from the
MAC/IP route advertisements in EVPN, hence:
a) Allows the clean and clear advertisements of ipv4 or ipv6 prefixes
in an NLRI with no MAC addresses in the route key, so that only IP
information is used in BGP route comparisons.
b) Since the route type is different from the MAC/IP Advertisement
route, the advertisement of prefixes will be excluded from all the
procedures defined for the advertisement of VM MACs, e.g. MAC
Mobility or aliasing. As a result of that, the current [RFC7432]
procedures do not need to be modified.
c) Allows a flexible implementation where the prefix can be linked to
different types of overlay indexes: overlay IP address, overlay
MAC addresses, overlay ESI, underlay IP next-hops, etc.
d) An EVPN implementation not requiring IP Prefixes can simply
discard them by looking at the route type value. An unknown route
type MUST be ignored by the receiving NVE/PE.
7. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
8. Security Considerations
The security considerations discussed in [RFC7432] apply to this
document.
9. IANA Considerations
This document requests the allocation of value 5 in the "EVPN Route
Types" registry defined by [RFC7432] and modification of the registry
as follows:
Value Description Reference
5 IP Prefix route [this document]
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6-255 Unassigned
10. References
10.1 Normative References
[RFC4364]Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2006,
<http://www.rfc-editor.org/info/rfc4364>.
[RFC7432]Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet
VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, <http://www.rfc-
editor.org/info/rfc7432>.
[EVPN-INTERSUBNET] Sajassi et al., "IP Inter-Subnet Forwarding in
EVPN", draft-ietf-bess-evpn-inter-subnet-forwarding-03.txt, work in
progress, February, 2017
10.2 Informative References
[EVPN-OVERLAY] Sajassi-Drake et al., "A Network Virtualization
Overlay Solution using EVPN", draft-ietf-bess-evpn-overlay-07.txt,
work in progress, November, 2016
11. Acknowledgments
The authors would like to thank Mukul Katiyar for their valuable
feedback and contributions. The following people also helped
improving this document with their feedback: Tony Przygienda and
Thomas Morin.
12. Contributors
In addition to the authors listed on the front page, the following
co-authors have also contributed to this document:
Senthil Sathappan
Florin Balus
Aldrin Isaac
Senad Palislamovic
13. Authors' Addresses
Jorge Rabadan (Editor)
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Nokia
777 E. Middlefield Road
Mountain View, CA 94043 USA
Email: jorge.rabadan@nokia.com
Wim Henderickx
Nokia
Email: wim.henderickx@nokia.com
John E. Drake
Juniper
Email: jdrake@juniper.net
Ali Sajassi
Cisco
Email: sajassi@cisco.com
Wen Lin
Juniper
Email: wlin@juniper.net
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