Subject: [Idr] Clarification about MP (rfc4760)

From: "Thomas Mangin" <[email-masked]>
Date: Mon, 24 Aug 2015 17:05:21 +0100

Hello,

I am seeking clarification on how an implementation implementing RFC 
4760 should behave when it does not announce the family IPv4/Unicast but 
receive it from its peers and then:
  - receive an UPDATE with normal IPv4 routes
  - receive a MP_(U)REACH update with IPv4 NLRI
As it would seems that some implementation send normal IPv4 NLRI even if 
the MP negotiation is excluding this family.

For the later, the best I found was 
https://tools.ietf.org/html/draft-ietf-idr-error-handling-19#section-5.4 
which ignores ignore typed NLRI not announced.
I assume it would be logical to behave the same way for the former.

Sorry if this was already clarified and if I missed it - my googling and 
use of tools.ietf.org would have failed me.

Thank you,

Thomas

---

From: Jeffrey Haas <[email-masked]>
Date: Thu, 27 Aug 2015 12:02:41 -0400

On Mon, Aug 24, 2015 at 05:05:21PM +0100, Thomas Mangin wrote:
> 4760 should behave when it does not announce the family IPv4/Unicast
> but receive it from its peers and then:
> As it would seems that some implementation send normal IPv4 NLRI
> even if the MP negotiation is excluding this family.

When the multi-protocol extensions were introduced, initially covering
adding multicast reachability, there really wasn't any provision made to
*exclude* existing IPv4-unicast behavior if the capability wasn't announced.
At best, if you announce the capability, it suggests that you could encode
ipv4-unicast in the MP section if you wanted to.

There was also a rather ugly mess covering SAFI 3, but thankfully we got
beyond that. :-)

> For the later, the best I found was https://tools.ietf.org/html/draft-ietf-idr-error-handling-19#section-5.4

I wouldn't apply this to regular IP reachability.  The typed routes in
question are literally route types, 1..N in the NLRI in question.  Basically
structured routes that derive a portion of their structure from a type
field.

-- Jeff