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

CiscoNSP List CiscoNSP_list at hotmail.com
Wed Sep 27 12:44:55 EDT 2017 

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.


________________________________
From: cisco-nsp <cisco-nsp-bounces at puck.nether.net> on behalf of CiscoNSP List <CiscoNSP_list at hotmail.com>
Sent: Thursday, 28 September 2017 1:53 AM
To: Mattias Gyllenvarg; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP not advertising supernet to RR's

Hi,


Thanks for the reply - route-map show its  getting a hit for the supernet (And redist statements are not new unfortunately) - The route is in bgp table, and being advertised to upstreams.....just not to our  RRs....I did some further checking post identifying the "no community tag" issue - It seems all "other" static and connected routes are being tagged with the correct communities (And therefore, and being advertised to our RRs(route-map filters based on community tag).....Ive had a bit of a google, but found nothing (yet)....but is this "normal" behavior for a Cisco? To not tag static routes to Null0 with communities.....seems very odd, but all other static routes/and connected are being tagged.....just not the supernet?


Thanks in advance.


________________________________
From: Mattias Gyllenvarg <mattias at gyllenvarg.se>
Sent: Tuesday, 26 September 2017 4:32 PM
To: CiscoNSP List; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP not advertising supernet to RR's

You can test the hits in the route-map with "sh ip bgp route-map G----_RANGES" and see if it hits correctly.

If the redist statements are new then they will take time to be implemented, 20min I think for a full BGP rerun. If you are in a hurry, remove and re add the route.

Do you receive this route via BGP aswell? Perhaps this is not the best route as BGP sees it.

tis 26 sep. 2017 kl 08:10 skrev CiscoNSP List <CiscoNSP_list at hotmail.com<mailto:CiscoNSP_list at hotmail.com>>:
Hi Everyone,


Have a problem with supernet being advertised from an ASR1006 to our RR's - Prefix is in the routing table, and in bgp, but the router is only advertising smaller prefixes to the RR's (/30,/29, 28 etc)...I

dont *think* its due to the PL (As it should be allowing anything less that /32...which it appears to be doing as /30,/29 etc are being advertised?)


Appreciate any assistance.


** Ah - Update, just noticed as I was about to hit send that the supernet is not being tagged with any community.....smaller prefixes are though? So route-map is tagging "some" prefixes within the

supernet?


router bgp 1***6
 address-family ipv4
  redistribute connected route-map G----_RANGES
  redistribute static route-map G----_RANGES


neighbor xxx.xxx.76.204 route-map TO_ME1_RR out


route-map TO_ME1_RR permit 10
 match community CL_G----_RANGES
route-map TO_ME1_RR permit 20
 match community CL_G----_CUST_BGP_RANGES
route-map TO_ME1_RR permit 30
 match community CL_DEFAULT_ROUTE


ip community-list standard CL_G----_RANGES permit 1***6:1301
ip community-list standard CL_G----_RANGES permit 1***6:1302


route-map G----_RANGES permit 10
 match ip address prefix-list PL_G----_PREFIXES
 set community 1***6:1000 1***6:1301 1***6:11000
route-map G----_RANGES permit 20
 match ip address prefix-list PL_N***S_PREFIXES
 set community 1***6:1400


ip prefix-list PL_G----_PREFIXES description G---- _PREFIXES
ip prefix-list PL_G----_PREFIXES seq 5 permit xxx.xxx.xxx.xxx.0/20 le 32
ip prefix-list PL_G----_PREFIXES seq 10 permit yyy.yyy.yyy.yyy/21 le 32



#sh ip prefix-list PL_G----_PREFIXES seq 5
   seq 5 permit xxx.xxx.xxx.xxx.0/20 le 32 (hit count: 4833, refcount: 1)


#sh ip route xxx.xxx.xxx.xxx.0 255.255.240.0
Routing entry for xxx.xxx.xxx.xxx.0/20, supernet
  Known via "static", distance 1, metric 0 (connected)
  Redistributing via bgp 1***6, ospf 100
  Advertised by bgp 1***6 route-map G----_RANGES
  Routing Descriptor Blocks:
  * directly connected, via Null0
      Route metric is 0, traffic share count is 1


#sh ip bgp xxx.xxx.xxx.xxx.0 255.255.240.0
BGP routing table entry for xxx.xxx.xxx.xxx.0/20, version 311740657
Paths: (1 available, best #1, table default)
  Advertised to update-groups:
     544        552        555        591
  Refresh Epoch 1
  Local
    0.0.0.0 from 0.0.0.0 (xxx.xxx.76.253)
      Origin IGP, metric 0, localpref 100, weight 32768, valid, sourced, local, best
      rx pathid: 0, tx pathid: 0x0


#sh ip bgp neighbors xxx.xxx.76.204 advertised-routes

 *>  xxx.xxx.xxx.xxx.32/30 0.0.0.0                  0         32768 ?
 *>  xxx.xxx.xxx.xxx.40/30 0.0.0.0                  0         32768 ?
 *>  xxx.xxx.xxx.xxx.72/29 xxx.xxx.xxx.xxx.90            0         32768 ?
 *>  xxx.xxx.xxx.xxx.88/30 0.0.0.0                  0         32768 ?
 *>  xxx.xxx.xxx.xxx.100/30
                       0.0.0.0                  0         32768 ?
     Network          Next Hop            Metric LocPrf Weight Path
 *>  xxx.xxx.xxx.xxx.112/28
                       xxx.xxx.78.230           0         32768 ?
 *>  xxx.xxx.xxx.xxx.136/30
                       xxx.xxx.78.230           0         32768 ?
 *>  xxx.xxx.xxx.xxx.164/30
                       xxx.xxx.xxx.xxx.102           0         32768 ?


Thanks


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