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Re: VPN-IPv4 routes

  • From: "Rohit Gupta" <rohitgupta416@indiatimes.com>
  • Date: Mon, 05 Apr 2004 12:02:47 +0530
  • CC: "Roger Pottier"<roger_pottier@yahoo.com>, <l3vpn@ietf.org>, <mpls@UU.NET>
  • X-URL: http://indiatimes.com

No Rajesh, there is nothing in the BGP spec which says that the path attributes should be processed in order of their absolute type codes.

There is thus nothing wrong with MP_UNREACH_NLRI coming before MP_REACH_NLRI 

~Rohit

"Rajesh Potti" wrote:

Hi Robert,

 Another issue on similiar lines:
  When MP_REACH_NLRI and MP_UNREACH_NLRI are found in the same UPDATE, is there a particular order enforced?
  MP_REACH_NLRI has type code 14, and MP_UNREACH_NLRI has type code 15, hence should it be
  MP_REACH_NLRI followed by MP_UNREACH_NLRI in the same UPDATE.

Rajesh

Robert Raszuk wrote:

Hi Roger,

 > If they are present in the same UPDATE, and it also has a BGP Extended
 > Community attribute (Type code= 16) would the MP_UNREACH_NLRI also be
 > interpreted as, for those VRFs which are importing those route
 > targets?

Nope. For unreachable information in any address family none of the
attributes (incl BGP ext community attribute) are important and not
considered. Remember that the NLRI format there still is RD:IPv4 so it
uniquely identifies all by itself which remote destinations became
unreachable.

In other words checking against RTs would be required on the withdraw
only if any other PE would inject new set of RTs for previously
advertised VPNv4 routes before withdrawing those apriori. That would be
an illegal operation.

Cheers,
R.

 > Roger Pottier wrote:
 >
> Hi,
>
>  RFC 2858 (Multiprotocol Extensions for BGP) specifies how MP_REACH_NLRI
>  and MP_UNREACH_NLRI is carried in a packet. Can a single BGP Update
> packet contain both MP_REACH_NLRI (Type code = 14) and MP_UNREACH_NLRI
> (Type code=15). I saw an implementation, sending both the path
> attributes in the same
>  UPDATE.
>
> If they are present in the same UPDATE, and it also has a BGP Extended
> Community attribute (Type code= 16) would the MP_UNREACH_NLRI also be interpreted
> as, for those VRFs which are importing those route targets?
>
> Roger
>
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-- 
Rajesh Potti.
 

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