Multi-Protocol BGP

[F Martinez]

Hello,

How do we know or verify that Multi-Protocol BGP is configured on a router?
Can you please give me an example configuration. I have an idea about this but I just want to make sure that I'm correct.

Thanks in advance!

[Vinit Jain · Accepted solution]

Hello,

If you run through the BGP configuration using "show run | sec router bgp " or "show run | begin router bgp", you will notice multiple address-families configured such as 

address-family vpnv4 unicast or address-family vpnv6 unicast, address-family ipv6 unicast or different AFI / SAFI configuration other than address-family ipv4 unicast.

Hope this helps

Let me know if you have any specific question.

Regards

Vinit

PS: Please rate useful posts. Please mark the question as answered if your query has been resolved

[F Martinez]

Thank you Vinit

Got another question. Hope you don't mind.
Why should we use Multi-Protocol BGP than the regular BGP?

[Vinit Jain · Accepted solution]

First of all, different address-family prefixes have different format. say for IPv4 address format is different than IPv6 format. VPN-IPv4 prefixes have a different format, L2VPN prefixes have a different format etc.

for each address-family, there are different NLRI formats defined in various RFCs and not just IPv4 address-family format. For example VPN-IPv4 prefixes are in the formation RD:IP-address/prefix-len (1:1:192.168.1.1/32). The VPN prefix is also assigned a VPN label. both the prefix and label information cannot be carried with just IPv4 address-family. it is carried with vpnv4 address-family. Refer to the below RFC for more details on carrying label with BGP-4 updates:

https://tools.ietf.org/html/rfc3107

For reference take a look at another RFC:

https://tools.ietf.org/html/rfc5549

This defines how IPv4 NLRI can be advertised with IPv6 next-hop and there are different RFC's based on different feature sets or address-families which you can refer to understand the format.

Hope this clarifies.

Regards

Vinit

[F Martinez]

Okay - one more thing. :)

Is address-family ipv4 unicast the default if you don't configure address family under the BGP configuration?

[Vinit Jain]

Yes. That is correct. remember, if you do not configure "no bgp default ipv4-unicast" and if you configure a neighbor statement, it will try to establish IPv4 peering with the remote BGP speaking router.

Hope this answers your question

Regards

Vinit

[F Martinez]

Yes, this answered my question. Thanks a lot!