Cisco Cisco IOS Software Release 12.4(4)T Dati aggregati
Product Bulletin
© 2009 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.
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2) Release 12.4(24)T Highlights
Table 1.
Release 12.4(24)T Feature Highlights
2.1.1) BGP 4-byte ASN Support
2.1.2) Mobile IP—Policy and
Application-Based Routing for Mobile
Router Multi-Path Support
2.1.3) Multi-VRF Selection using
Policy-Based Routing (PBR)
2.1.2) Mobile IP—Policy and
Application-Based Routing for Mobile
Router Multi-Path Support
2.1.3) Multi-VRF Selection using
Policy-Based Routing (PBR)
2.3.1) Web Services
Management Agent
(WSMA)
2.3.2) Smart Call Home
Support for the Cisco
7200 Series Router
Management Agent
(WSMA)
2.3.2) Smart Call Home
Support for the Cisco
7200 Series Router
2.1) IP Routing
2.1.1) Cisco IOS BGP Support for 4-byte Autonomous System Numbers (ASN)
Border Gateway Protocol (BGP) is an Internet Engineering Task Force (IETF) standard, and the
most scalable of all routing protocols. BGP is the routing protocol of the global Internet, as well as
for enterprise and service provider private networks. BGP has expanded upon its original purpose
of carrying Internet reachability information, and can now carry routes for Multicast, IPv6, VPNs,
and a variety of other data. Cisco supports all IETF BGP standards, as well as the majority of
Internet Drafts for BGP. In addition, Cisco is an active participant in the Inter-Domain Routing (IDR)
Working Group at IETF, and a frequent contributor of new BGP extensions.
Border Gateway Protocol (BGP) is an Internet Engineering Task Force (IETF) standard, and the
most scalable of all routing protocols. BGP is the routing protocol of the global Internet, as well as
for enterprise and service provider private networks. BGP has expanded upon its original purpose
of carrying Internet reachability information, and can now carry routes for Multicast, IPv6, VPNs,
and a variety of other data. Cisco supports all IETF BGP standards, as well as the majority of
Internet Drafts for BGP. In addition, Cisco is an active participant in the Inter-Domain Routing (IDR)
Working Group at IETF, and a frequent contributor of new BGP extensions.
Cisco IOS Software Release 12.4(24)T release adds BGP Support for 4-byte ASN.
At the early time of BGP development and standardization, it was assumed that availability of a 16
bit binary number to identify the Autonomous System (AS) within BGP would have been more than
sufficient. The 16 bit AS number, also known as the 2-byte AS number, provides a pool of 65,536
unique Autonomous System numbers. The Internet Assigned Numbers Authority (IANA) manages
the available BGP Autonomous System Numbers (ASN) pool, with the assignments being carried
out by the Regional Registries.
bit binary number to identify the Autonomous System (AS) within BGP would have been more than
sufficient. The 16 bit AS number, also known as the 2-byte AS number, provides a pool of 65,536
unique Autonomous System numbers. The Internet Assigned Numbers Authority (IANA) manages
the available BGP Autonomous System Numbers (ASN) pool, with the assignments being carried
out by the Regional Registries.
The current consumption rate of public AS numbers suggests that the entire 2-byte ASN pool will
be fully depleted by early to middle 2011. A solution to this depletion is the expansion of the
existing 2-byte AS number to a 4-byte AS number, which provides a theoretical 4,294,967,296
unique AS numbers. ARIN has made the following policy changes in conjunction with the adoption
of the solution.
be fully depleted by early to middle 2011. A solution to this depletion is the expansion of the
existing 2-byte AS number to a 4-byte AS number, which provides a theoretical 4,294,967,296
unique AS numbers. ARIN has made the following policy changes in conjunction with the adoption
of the solution.
As of January 1, 2009, per the American Registry for Internet Numbers (ARIN), all new
Autonomous System Numbers (ASNs) issued will be 4-byte by default, unless otherwise requested.
For more information please visit:
Autonomous System Numbers (ASNs) issued will be 4-byte by default, unless otherwise requested.
For more information please visit:
The Cisco IOS BGP 4-byte ASN feature allows BGP to support the ASN encoded as a 4-byte
entity. The addition of this feature allows an operator to use an expanded 4-byte AS number
granted by IANA.
entity. The addition of this feature allows an operator to use an expanded 4-byte AS number
granted by IANA.
As shown in Figure 5 below, backwards compatibility is provided between the 4-byte and 2-byte AS
numbers, since BGP and Multiprotocol BGP is already widely deployed in ISP and MPLS VPN
environments. Specifically, advertisement via standard based BGP capability code, two new
“optional transitive” attributes: AS4_AGGREGATOR and AS4_PATH, and a newly reserved AS
TRANS#: 23456 for interoperability between 4 bytes ASN capable and non-capable BGP speakers
are introduced to a smooth migration from a 2-byte to a 4-byte ASN environment.
numbers, since BGP and Multiprotocol BGP is already widely deployed in ISP and MPLS VPN
environments. Specifically, advertisement via standard based BGP capability code, two new
“optional transitive” attributes: AS4_AGGREGATOR and AS4_PATH, and a newly reserved AS
TRANS#: 23456 for interoperability between 4 bytes ASN capable and non-capable BGP speakers
are introduced to a smooth migration from a 2-byte to a 4-byte ASN environment.