Internet Engineering Task Force Francis Dupont
INTERNET DRAFT ENST Bretagne
Expires in August 2001 Alain Durand
SUN Microsystems
February 22, 2001
BGP4 router ID for IPv6 only routers
<draft-dupont-durand-idr-ipv6-bgp-routerid-00.txt>
Status of this Memo
This document is an Internet Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its
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Distribution of this memo is unlimited.
Abstract
BGP4 [1] uses a 32 bit field to identify a router (the so called
"router ID"). In IPv4 domain, an IPv4 address of the router is
typically used in this field. In an IPv6 routing domain, routers
may very well not have any IPv4 addresses. This document provides
a simple way to form a globally unique ID in such a case.
1. Introduction
BGP4 [1] extension for IPv6 are defined in [2] and [3].
However, BGP4 uses a 32 bit field known as the router ID.
This router ID is used in:
- BGP Identifier in OPEN messages (local use)
- AGGREGATOR (optional transitive) attributes.
- ORIGINATOR_ID (optional non-transitive) attributes [4]
- CLUSTER_LIST (optional non-transitive) attributes [4]
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AGGREGATOR attributes contain an Autonomous System (AS) number
with the IP address of the BGP speaker that formed the aggregate
route. It is the only transitive (i.e. non local) use of the
router ID.
The router ID should be somehow unique and BGP implementations
should provide a way to manually set it. This field typically
contains one of the IPv4 addresses of the BGP4 speaker.
In an IPv6 domain, some router may have many IPv4 addresses,
and some other may very well not have any. On those routers,
one cannot assigned random values to the router ID, as it could
conflict with the router ID derived from an IPv4 addresses on
another dual stack router.
This document specifies a simple way to construct a somehow
globally unique 32 bit router ID. This document does not look
at a more longer term solution that would consist in changing
the size of the routing ID field.
2. Solution
In the absence of a globally unique IPv4 address on the router,
the 32 bit routing ID is constructed with:
- 4 bits set to one (as for an old reserved class E IPv4 address)
- 16 bits set to the AS number (a global AS number SHOULD be used
if the router ID can be seen outside the routing domain).
- 12 bits manually allocated within the domain. This allow for
4096 different router IDs in each routing domain.
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------+-------------------------------+-----------------------+
| | | |
| 0xF | AS Number | Locally allocated |
| | | |
+-------+-------------------------------+-----------------------+
3. Security Considerations
The usage of fake IPv4 address of this form minimizes accidental
or deliberate confusions (ie. same router ID for two different
BGP speakers).
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4. References
[1] Y. Rekhter, T. Li, "A Border Gateway Protocol 4 (BGP-4)",
RFC 1771, March 1995.
[2] T. Bates, Y. Rekhter, R. Chandra, D. Katz, "Multiprotocol
Extensions for BGP-4", RFC 2858, June 2000.
[3] P. Marques, F. Dupont, "Use of BGP-4 Multiprotocol Extensions
for IPv6 Inter-Domain Routing", RFC 2545, March 1999.
[4] T. Bates, R. Chandra, E. Chen, "BGP Route Reflection -
An Alternative to Full Mesh IBGP", RFC 2796, April 2000.
5. Author's Address
Francis Dupont
ENST Bretagne
Campus de Rennes
2, rue de la Chataigneraie
BP 78
35512 Cesson-Sevigne Cedex
FRANCE
Fax: +33 2 99 12 70 30
EMail: Francis.Dupont@enst-bretagne.fr
Alain Durand
SUN Microsystems, Inc
901 San Antonio Road
MPK17-202
Palo Alto, CA 94303-4900
USA
EMail: Alain.Durand@sun.com
Expire in 6 months (August 22, 2001)
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