Solved: multicast BGP

Konstantin Dunaev · ‎03-17-2008

Hi everybody,

I'm trying to configure the multicusting over mBGP and found that there are two possibilities to do it:

1. use the "address family ipv4 multicast"

2 use the "neighbor x.x.x.x nlri multicast"

is there any difference between those aproaches? I mean the difference in end-result of course :).

mohammedmahmoud · ‎03-17-2008

Hi,

Never tried the NLRI format, but the AFI (Address Family Identifier) format was introduced with multiprotocol BGP (mBGP) in Cisco IOS Release 12.0(2)S and Cisco IOS Release 11.1(20)CC and integrated into Cisco IOS Release 12.0(7)T. The AFI format is designed to be modular, scalable, and support multiple AFI and subsequent address-family identifier (SAFI) configurations, please check the below link:

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbhycli.html

BR,

Mohammed Mahmoud.

View solution in original post

mohammedmahmoud · ‎03-17-2008

Hi,

Never tried the NLRI format, but the AFI (Address Family Identifier) format was introduced with multiprotocol BGP (mBGP) in Cisco IOS Release 12.0(2)S and Cisco IOS Release 11.1(20)CC and integrated into Cisco IOS Release 12.0(7)T. The AFI format is designed to be modular, scalable, and support multiple AFI and subsequent address-family identifier (SAFI) configurations, please check the below link:

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbhycli.html

BR,

Mohammed Mahmoud.

Konstantin Dunaev · ‎03-17-2008

yes, it's all correct, but I'd like to now if there are any differences in multicast traffic flow or routing table between them.

if you search for something like "multicast BGP" on cisco.com you will find a lot of exaples which use "nlri" option to activate multicast.

mohammedmahmoud · ‎03-17-2008

Hi,

The difference is just in the configuration and the way BGP is going to exchange the information, with AFI the routing information is carried as appended attributes (multi protocol extensions), NLRI format has many drawbacks as many new features are supported only in AFI and SAFI configuration modes and cannot be configured in NLRI configuration modes, i quote from the above document regarding NLRI limitations:

"Limited support for multicast interdomain routing and incongruent multicast and unicast topologies. In the NLRI format, not all configuration options are available, and these configuration are more complex. If the routers in the infrastructure do not have multicast capabilities, or if policies differ as to where multicast traffic is configured to flow, multicast routing cannot be supported."

BR,

Mohammed Mahmoud.

Konstantin Dunaev · ‎03-17-2008

ok, thank you, it's more clear then.

I was just curious that that are so many multicast BGP examples with nlri option and very few with address-family.

mohammedmahmoud · ‎03-17-2008

hi,

You are very welcomed, and if you are interested in more details, you can check the Multiprotocol Extensions for BGP-4 RFC 2858:

http://www.ietf.org/rfc/rfc2858.txt

BR,

Mohammed Mahmoud.