BGP use of Loopback interfaces

[aconticisco]

Hi,

have seen it a few times that Loopback interfaces are used for iBGP routers to establish the neighbour connection instead of the direct physical interface,

Is this done bacuase the Loopback interfaces are always up (but then I ask if the physical interface/link goes down is it not the same result!) does this also imply that an IGP such as OSPF or EIGRP needs to be run to provide the communication between the loopback interfaces that is necessary to establish iBGP connectivity ?

Thanks 

[Mark Malone · Accepted solution]

Hi

whether you use a loopback or a physical interface you will always require an IGP with IBGP because its not a routing protocol its a transport L4 protocol so the IGP informs it how to get places as BGP has no concept of that so the IGP is required

Loopbacks are chosen for IBGP because there always up so once the IGP has a path to the Loopback the IBGP session will stay up , not required in EBGP as usually only 1 path between the 2 points