FTOS Configuration Guide for the C-Series - Force10 Networks

Next Hop
The Next Hop is the IP address used to reach the advertising router. For EBGP neighbors, the
Next-Hop address is the IP address of the connection between the neighbors. For IBGP, the
EBGP Next-Hop address is carried into the local AS. A Next Hop attribute is set when a BGP speaker
advertises itself to another BGP speaker outside its local AS. It can also be set when advertising routes
within an AS. The Next Hop attribute also serves as a way to direct traffic to another BGP speaker, rather
than waiting for a speaker to advertise.
FTOS allows you to set the Next Hop attribute in the CLI. Setting the Next Hop attribute lets you
determine a router as the next hop for a BGP neighbor.
Implementing BGP with FTOS
4-Byte AS Numbers
FTOS Version 7.7.1 supports 4-Byte (32-bit) format when configuring Autonomous System Numbers
(ASNs). The 4-ByteByte 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 48 4-Byte ASN Dot Format Examples
Traditional Format Dot Format
65001 Is 0.65501
65536 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.
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