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New Member

piggybacking label in bgp update

Hi,

Label can be piggybacked in the BGP Update message by using the BGP-4 Multiprotocol Extensions attribute [RFC 2283]. The label is encoded into the NLRI field of the attribute, and the SAFI ("Subsequent Address Family Identifier") field is used to indicate that the NLRI contains a label.

Could anybody would confirm what would be the SAFI value for such piggybacking (though rfc 3107 presumes a value of 4),and also what could be the SAFI value for BGP carrying vpn4 routes with label piggybacked in it??

Thanks

Anand

5 REPLIES
Purple

Re: piggybacking label in bgp update

Anand,

The SAFI value will once again be 4.

Here's a link to the list of current SAFI values:

http://www.iana.org/assignments/safi-namespace

Hope that helps - pls rate the post if it does.

Paresh.

Here'sa

Purple

Re: piggybacking label in bgp update

Just an addendum to my last post...

The Subsequent Address Family Identifier provides additional information about the type of the Network Layer Reachability Information carried in the BGP attribute.

The SAFI is used to qualify the AFI associated with it. So when you use a SAFI value of 4, this means that the Network Layer Reachability Information associated with the AFI is carried with MPLS Labels.

Hope that helps - pls rate the post if it does.

Paresh

New Member

Re: piggybacking label in bgp update

Paresh,

However,its also says SAFI value of 128 for MPLS labeled VPN adress,whats the difference between these two(i,e 4&128)??

Thanks

Anand

New Member

Re: piggybacking label in bgp update

Paresh,

The SAFI value for NLRI carrying vpn routes would be 128,Refer http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hirp_c/ch05/brbover.htm

where it says ""RFC 3107 specifies how to add label information to multiprotocol BGP address families using a SAFI. The Cisco IOS implementation of MPLS uses RFC 3107 to provide support for sending IPv4 routes with a label. VPNv4 routes implicitly have a label associated with each route""

Thanks

Anand

Purple

Re: piggybacking label in bgp update

Actually, Anand, you are right...

The value of 4 is only used when the network layer protocol is IPv4, IPv6 etc. For vpnv4 routes in the rfc2547bis format, the SAFI will be 128..

Regards,

Paresh

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