The MPLS WG Archive

[Janardan Ramesh <JRamesh@shastanets.com>]

RFC-2547.bis says that format for vpn-ipv4 address
is 8 byte RD + 4 byte prefix. Suresh sent out a
question regarding the prefix length.

In the reply received from Yakov, it said that the
prefix length is endoded as per multiprotocol extensions to
BGP (rfc2858).

My undertanding of the MPLS_REACH_NLRI (based on 2858 and
carrying labels in BGP draft is as follows)


NLRI Len (1 byte), Label (3bytes), NLRI variable.

The draft says that the length includes the length of the label and
the NLRI length.


For the VPN-ipv4 case, the MP_REACH_NLRI will look like

NLRI Len (1byte) = 14, Label (bytes), NLRI Len=prefixlen, 8 byte NLRI + 4
byte prefix.

I feel that this model has deviated from the representation of IP prefix in
traditional
ipv4 BGP.

Should the format for vpn-ipv4 address be as follows?

8 byte RD + 1 byte prefix len + 4 bytes prefix  (with trailing zeros)

What is the current format used both when conveying the information
and storing the routes in the routing table?

Regards
Ramesh