Dell Force10 E600i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 205

Ignore Router-ID for some best-path calculations FTOS 8.3.1.0 and later allow you to avoid unnecessary BGP best-path transitions between external paths under certain conditions. The bgp bestpath router-id ignore command reduces network disruption caused by routing and forwarding plane changes and allows for faster convergence. 4-Byte AS Numbers FTOS Version 7.7.1 and later support 4-Byte (32-bit) format when configuring Autonomous System Numbers (ASNs). The 4-Byte support is advertised as a new BGP capability (4-BYTE-AS) in the OPEN message. If a 4-Byte BGP speaker has sent and received this capability from another speaker, all the messages will be 4-octet. The behavior of a 4-Byte BGP speaker will be different with the peer depending on whether the peer is 4-Byte or 2-Byte BGP speaker. Where the 2-Byte format is 1-65535, the 4-Byte format is 1-4294967295. Enter AS Numbers using the traditional format. If the ASN is greater than 65535, the dot format is shown when using the show ip bgp commands. For example, an ASN entered as 3183856184 will appear in the show commands as 48581.51768; an ASN of 65123 is shown as 65123. To calculate the comparable dot format for an ASN from a traditional format, use ASN/65536. ASN%65536. Table 12-2. 4-Byte ASN Dot Format Examples Traditional Format Dot Format 65001 65536 Is 0.65501 The 1.0 100000 Same As 1.34464 4294967295 65535.65535 When creating Confederations, all the routers in a Confederation must be either 4-Byte or 2-Byte identified routers. You cannot mix them. Configure the 4-byte AS numbers with the four-octect-support command. AS4 Number Representation FTOS version 8.2.1.0 supports multiple representations of an 4-byte AS Numbers: asplain, asdot+, and asdot. Note: The ASDOT and ASDOT+ representations are supported only in conjunction with the 4-Byte AS Numbers feature. If 4-Byte AS Numbers are not implemented, only ASPLAIN representation is supported. ASPLAIN is the method FTOS has used for all previous FTOS versions.It remains the default method with FTOS 8.2.1.0 and later. With the ASPLAIN notation, a 32 bit binary AS number is translated into a decimal value. Border Gateway Protocol IPv4 (BGPv4) | 205