User guide

Configuring BGP BGP Overview
OmniSwitch AOS Release 7 Advanced Routing Configuration Guide March 2015 page 4-7
• Support for two new optional transitive attributes AS4_PATH and AS4_AGGREGATE. These
attribute are used when new BGP speakers are interacting with OLD BGP speaker.
• To establish a neighbor relationship between non-mappable BGP 4-octet ASNs with BGP 2-octet
ASNs the reserved 2-octet ASN AS_TRANS 23456 is used.
• The 4-octet AS Specific Extended Community as specified in RFC 5668 will be used with non-
mappable 4-octet ASNs. If the ASN is mappable to 2-octet, the 2-octet AS specific extended
community will still be used.
• The 4-octet ASN is represented in one of three ways:
– - asplain (simple decimal notation)
– - asdot+ (two 16-bit values as low-order and high-order)
– - asdot (a mixture of asplain and asdot+).
The command ip bgp asn-format configures the display format to be used when displaying 4-octet ASNs.
This configuration changes only the output format. The input format can be in any mode when
representing the ASN.
The following examples show how to configure the local BGP ASN as 65535 in the three different
formats:
-> ip bgp autonomous-system 65535 (asplain format)
-> ip bgp autonomous-system 0.65535 (asdot+ format)
-> ip bgp autonomous-system 65535 (asdot format)
The following examples show how to configure the local BGP ASN as 65538 in the three different
formats:
-> ip bgp autonomous-system 65538 (asplain format
-> ip bgp autonomous-system 1.2 (asdot+ format)
-> ip bgp autonomous-system 1.2 (asdot format)
The following examples show how to configure the BGP neighbor ASN as 65535 in the three different
formats:
-> ip bgp neighbor 2.2.2.2 remote-as 65535 (asplain format)
-> ip bgp neighbor 2.2.2.2 remote-as 0.65535 (asdot+ format)
-> ip bgp neighbor 2.2.2.2 remote-as 65535 (asdot format)