[j-nsp] JunOS interop problems with RFC5549

[Bjørn Mork]

Brian Rak <brak at gameservers.com> writes:

> I'm running into an issue where JunOS will not accept BGP updates
> containing a MP_REACH_NLRI attribute with a 32 byte nexthop.  As soon
> as I send one, the session gets closed and the following logged:
>
> rpd[16187]: bgp_read_v4_update:12111: NOTIFICATION sent to
> fe80::ae1f:6bff:fe8a:435d (External AS 64555): code 3 (Update Message
> Error) subcode 9 (error with optional attribute)
> rpd[16187]: Received malformed update from fe80::ae1f:6bff:fe8a:435d
> (External AS 64555)
> rpd[16187]:   Family inet-unicast, prefix 0.0.0.0/0
> rpd[16187]:   Malformed Attribute MP_REACH(14) flag 0x80 length 42.
>
> The other end of the BGP session is a Cumulus router (or a linux
> machine running FRR).  If I patch that end to only send 16 byte
> nexthops, JunOS accepts the route and seems to work just fine.
>
> RFC5549 states:
>
>>   o  Length of Next Hop Address = 16 or 32
>>   o  Next Hop Address = IPv6 address of next hop (potentially followed
>       by the link-local IPv6 address of the next hop).  This field is to
>       be constructed as per Section 3 of [RFC2545].


and also:

   A BGP speaker MUST only advertise to a BGP peer the IPv4 or VPN-IPv4
   NLRI with an IPv6 Next Hop if the BGP speaker has first ascertained
   via BGP Capability Advertisement that the BGP peer supports the
   Extended Next Hop Encoding capability for the relevant AFI/SAFI pair.


And I guess your Cumulus router failed to do this?


Bjørn