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Why BGP need an IGP

sugatada9
Level 1
Level 1

Hi,

guys I have a question here. I saw BGP always needs another protocol like OSPF or EIGRP etc. to propegate routes. Why this is so? Also the same route propegation can be done with BGP

Network

command?                 

1 Accepted Solution

Accepted Solutions

Harold Ritter
Cisco Employee
Cisco Employee

Hi Sugata,

This is mostly the case with iBGP, which is generally configured using the router loopback interface address rather than the directly connected interface address. This is very useful as the BGP session will not go down if the physical interface goes down as long as there is a backup path to the peer router loopback address. The IGP is used to establish the BGP session (TCP session) and to resolve the BGP next hop.

eBGP, on the other hand, is generally configured using the directly connected interface address.

Regards

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

View solution in original post

1 Reply 1

Harold Ritter
Cisco Employee
Cisco Employee

Hi Sugata,

This is mostly the case with iBGP, which is generally configured using the router loopback interface address rather than the directly connected interface address. This is very useful as the BGP session will not go down if the physical interface goes down as long as there is a backup path to the peer router loopback address. The IGP is used to establish the BGP session (TCP session) and to resolve the BGP next hop.

eBGP, on the other hand, is generally configured using the directly connected interface address.

Regards

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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