Tuesday, October 22, 2013

TTL for BGP packets

By default, an eBGP message has IP TTL of 1. When neighbors do not have a common network, or an eBGP router uses its loopback interface as an update source, the TTL value needs to be adjusted.
(config-router)# bgp neighbor IP_ADDR ebgp-multihop TTL_VALUE
In contrast, iBGP message has TTL of 255, and there is no need for extra configuration when using a loopback interface as an update source.
eBGP OPEN Message

iBGP OPEN Message

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