[c-nsp] BGP not advertising supernet to RR's

[CiscoNSP List]

Thanks James - Apologies for the top post.


I've tried static route to a loop, and it also matched successfully, but still no community tags


Yes - Ive tried clear ip bgp soft out  (And a hard clear also) - Still no luck


I dont see the /20 in sh ip bgp nei xxx adv-routes  (But as I am matching on community tags, I dont expect to....all the other prefixes within the /20 are being advertised)

debug bgp ipv4 etc on RR, I do not see any mention of the /20 (Only smaller prefixes (/29,/28,/24 etc)

debugging updates on PE when removal / re-add of supernet:  logs seem to state that the prefix is good post re-adding:

Sep 29 2017 00:02:40.276 aest: BGP(0): route 2cc.ccc.ccc.0/20 down
Sep 29 2017 00:02:40.276 aest: BGP: no valid path for 2cc.ccc.ccc.0/20
Sep 29 2017 00:02:40.276 aest: BGP(0): nettable_walker 2cc.ccc.ccc.0/20 no best path
Sep 29 2017 00:04:03.860 aest: BGP(0): route 2cc.ccc.ccc.0/20 up
Sep 29 2017 00:04:03.860 aest: BGP(0): route 2cc.ccc.ccc.0/20 up
Sep 29 2017 00:04:03.860 aest: BGP(0): nettable_walker 2cc.ccc.ccc.0/20 route sourced locally

...but, still no community tags (And not advertised to any peer)

#sh ip bgp 2cc.ccc.ccc.0 255.255.240.0
BGP routing table entry for 2cc.ccc.ccc.0/20, version 782198
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
  Not advertised to any peer
  Local
    0.0.0.0 from 0.0.0.0 (2vv.vvv.vvv.vv8)
      Origin IGP, metric 0, localpref 100, weight 32768, valid, sourced, local, best


Thanks again for your assistance.



________________________________
From: cisco-nsp <cisco-nsp-bounces at puck.nether.net> on behalf of James Bensley <jwbensley at gmail.com>
Sent: Thursday, 28 September 2017 6:22 PM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP not advertising supernet to RR's

On 27 September 2017 at 17:44, CiscoNSP List <CiscoNSP_list at hotmail.com> wrote:
>
> To answer my own question, I tested this by trying a /22 within the supernet statically routed to a next hop on the router....community tags applied correctly, prefix advertised to RR's, so then I tried routing the /22 to Null0 (Expecting it not to work - but it did? Community tags applied/RR advertisement worked).....so I tried the supernet again to null0, and again, it didnt get tagged with the correct communities, and no RR advertisement.....Need to revisit this again tomorrow, but the route-map / PL "looks" ok to me...matching the /20 le 32 - If the le 32 was the issue, you'd think the /22 would be impacted? I cant see anything else that would be causing the /20 to not get tagged though?
>
>
> Any suggestions are greatly appreciated.

What about when you set the static /20 route to a valid next-hopt IP,
not Null0? (e.g. a static route of a.fake.ip.addr which points to
Null0, and your /20 which points to a.fake.ip.addr).

Have you taken the usual action of performing a "soft clear out" on
the PE or "soft clear in" on the RR?

The /20 to Null0 route, do you see that on the PE in the output of
"show bgp ipv4 uni nei x.x.x.x advertised-routes" ?

If you see the /20 in the "advertised-routes" output, what do you see
on the RR when using "debug bgp ipv4 unicast updates pe.ip.addr.ess"
on the RR? (you will need to "flap" that static route).

If you don't see the /20 on in the "advertised-routes" output, what do
you see on the PE when using "debug bgp ipv4 unicast updates" [1] when
you remove and then re-add the static route, re-triggering the BGP
UPDATE?

Can you capture the BGP UPDATE message on the wire?

Can you replicate this in the lab, have you, what were the result?

Cheers,
James.

[1] Note that this could cause a lot of debugging output
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