Internet Draft Mark Bakke
<draft-bakke-dhc-snmp-trap-01.txt> Cisco
Standards Track
Expires May 2003
November 2002
DHCP Option for SNMP Notifications
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
The Dynamic Host Configuration Protocol [RFC1531] provides a method
for a host to retrieve common configuration parameters at boot time.
These include the host's IP address, default gateway, subnet mask,
DNS server, and other useful things.
When a host is booted from the network, it does not have access to
these configuration parameters from its local or network disk right
away; it relies instead on DHCP to provide them. One such parameter
that is not yet provided is a list of IP hosts to which to send SNMP
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notifications [RFC1448] during the boot process, particularly if the
boot fails. As the host is already gleaning similar information from
DHCP, a new option to specify these SNMP "trap" hosts appears to be
the simplest method to gain this information. Hosts not booting from
the network benefit as well, since SNMP notification hosts can now be
configured centrally through DHCP.
There are an increasing number of solutions that allow hosts, racks
of servers and embedded devices to be booted from the network. Many
of these solutions include 10s, 100s, or 1000s of identical thin
servers or blade servers which need to be monitored and managed
centrally. When a network boot fails, there is currently no standard
method to configure destinations to which to send SNMP notifications,
allowing corrective action to be taken.
This document describes a proposed DHCP option that specifies a list
of SNMP notification targets to which SNMP notifications should be
sent.
Acknowledgements
This draft was produced as a result of discussions with Keith
McCloghrie. Thanks also to David Harrington, Bert Wijnen, and Ira
McDonald for pointing out the (many) holes in the first version.
1. Terminology
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 [RFC2119].
2. DHCP Option
The snmp-notification-list option is a UTF-8 string consisting of a
comma-separated list of SNMP notification targets. SNMP notification
hosts SHOULD be listed in order of preference; an implementation
SHOULD send each notification to as many of the hosts listed as
possible.
Each target is a set of parameters, separated by the ASCII colon
character (':' = U+003a), which must appear in the following order:
- processor-model is a literal ASCII string which specifies one of
the message processing model values defined in [RFC2751] in
the SnmpMessageProcessingModel TC:
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v1 - SNMPv1
v2c - SNMPv2c
v3 - SNMPv3
This field must not be left blank.
- ip-address is specified as either a dotted-decimal IPv4 address,
a bracketed hexadecimal IPv6 address, or a DNS host name.
This field must not be left blank. Examples are:
10.1.50.100
[1080:0:0:0:8:800:200C:417A]
mytraphost.example.com
Note although the IPv6 format contains the colon character also
used as a field separator, the bracketed notation keeps the
two from being confused.
- udp-port is a decimal field containing the target UDP port. If
left blank, the default UDP port is 162.
- security-model is a literal ASCII string which specifies one
of the security models defined in [RFC2571] in the
SnmpSecurityModel TC:
v1 - SNMPv1
v2c - SNMPv2c
usm - User-Based Security Model
If the security-model field is left blank, no security is used.
The security-model field determines the format of the remainder of
the notification target string. If the security-model is v1 or v2c,
the next (optional) field is the community string:
- community-string specifies the community string to use when
sending notifications to the target. If not specified, the
default is "public".
If the security-model is "usm", two additional fields are required:
- security-level - This is the decimal security level number as
specified in [RFC2571] in the SnmpSecurityLevel TC:
noAuthNoPriv - No authentication, no privacy
authNoPriv - Authentication, with no privacy
authPriv - Authentication and privacy
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This field MUST be specified when using the user-based security
model.
- security-name - This is the UTF-8 security name to be used with
notifications to this target.
3. Examples
A group of two v3 targets, both using USM with authentication but no
privacy:
v3:128.1.2.3:162:usm:authNoPriv:joe,
v3:128.2.4.6:162:usm:authNoPriv:joe
(carriage return inserted for clarity)
A single v3 target, using USM with both authentication and privacy:
v3:128.1.5.9:162:usm:authPriv:bob
A single address that wants both v1 and v2c notifications with the
default community string and UDP port:
v1:10.1.1.1,v2c:10.1.1.1
An SNMPv2 address that uses a different community string:
v2c:10.50.2.100:my-community
4. Using Security Names
When using security names with the User-based Security Model, it is
assumed that each of the referenced security names has been
configured with its proper credentials, and can be used when sending
notifications. However, this may not always be true. When booting
the host from a network device, the configuration information for
these credentials is normally stored on the network device, in a
registry or configuration file. Events that cause notifications can
happen after receiving the snmp-notification-list DHCP option, and
before this configuration information is read from the device. When
sending an SNMPv3 notification using the user-based security model
(USM), these rules should be followed:
- If the security-level is "noAuthNoPriv", the security-name is
not necessary; send the notification as normal.
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- If the security-level is "authNoPriv", send the notification
without authentication as if it were "noAuthNoPriv". In this
case, it's probably better to send the alert unauthenticated
than not at all.
- If the security-level is "authPriv", do not send the notification.
5. Security Considerations
DHCP is normally deployed using authentication or security
mechanisms. Authentication is available using [RFC3118].
Potential exposures to attack when authentication is not being used
are discussed in section 7 of the DHCP protocol specification
[RFC2131]. Exposures when authentication is being used is described
in [RFC3118].
6. IANA Considerations
IANA is requested to allocate a DHCP option number for this option.
7. Summary
This document describes a DHCP option for configuring a list of SNMP
notification targets.
8. Normative References
[RFC2026] S. Bradner, "The Internet Standards Process", RFC 2026,
October 1996.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC2131] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[RFC1905] J. Case, K. McCloghrie, M. Rose, S. Waldbusser, "Protocol
Operations for SNMPv2", RFC 1905, January 1996.
[RFC2571] D. Harrington, R. Presuhn, B. Wijnen, "An Architecture for
Describing SNMP Management Frameworks", RFC 2571, April
1999.
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9. Informative References
[RFC2132] S. Alexander, R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC2939] R. Droms, "Procedures and IANA Guidelines for Definition of
New DHCP Options and Message Types", RFC 2939, September
2000.
[RFC3118] R. Droms, W. Arbaugh, "Authentication for DHCP Messages",
RFC 3118, June 2001.
Author Contact Information
Mark Bakke
Cisco Systems, Inc.
6450 Wedgwood Road
Maple Grove, MN
USA 55311
Voice: +1 763-398-1000
E-Mail: mbakke@cisco.com
10. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
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This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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