7.8.1.0 - Force10 Networks

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 6 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.
AS Number Migration
When migrating one AS to another, perhaps combining ASs, an eBGP network may lose its routing to an
iBGP if the ASN changes. Migration can be difficult as all the iBGP and eBGP peers of the migrating
network need to be updated to maintain network reachability. With this feature you can transparently
change the AS number of entire BGP network and ensure that the routes are propagated throughout the
network while the migration is in progress. Essentially, Local-AS provides a capability to the BGP speaker
to operate as if it belongs to "virtual" AS network besides its physical AS network.
138 Border Gateway Protocol