BGP and ebgp-multihop

Answered Question
Apr 11th, 2008

Hi,

My understanding of ebgp-multihop is that it increases the TTL so that we can reach for example a loopback interface whereby otherwise the packet would be dropped at the physical interface.

Q: When configuring iBGP with loopback addresses why is an equivalent of ebgp-multihop not required ?


Regards,


Phil.

Correct Answer by Jon Marshall about 8 years 10 months ago

Phil


Because it is a requirement for EBGP but not IBGP. Basically IBGP uses the internal IGP ie. EIGRP/OSPF to have reachability to other IBGP peers or there is a fulll IBGP mesh, one or the other, but EBGP is between 2 separate AS's so there is no IGP being run between the 2.


Jon

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Correct Answer
Jon Marshall Fri, 04/11/2008 - 05:03

Phil


Because it is a requirement for EBGP but not IBGP. Basically IBGP uses the internal IGP ie. EIGRP/OSPF to have reachability to other IBGP peers or there is a fulll IBGP mesh, one or the other, but EBGP is between 2 separate AS's so there is no IGP being run between the 2.


Jon

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