Re: BGP routes flap with neighbor weight command

Bill19795_2 · ‎01-27-2011

I am trying to simulate our production network in a lab to implement an internet failover project. The purpose right now is not the external internet BGP routing but the internal routing from the MPLS provider and how I advertise the default route to the remote sites. Currently I am setting up a mockup of our network in the lab and I am having a problem getting the routing to work with my test “MPLS” provider. On my production equipment I am using BGP to the provider and EIGRP internally. I have all of the redistribution setup and I am using the weight command on the BGP router to prefer the locally learned BGP route from the EIGRP routes learned internally. (Thanks Guiseppe!!)

Everything works great on the production network but when I use the weight command on HQR1 or RS1R1 in my lab to my “MPLS” provider the routes flap and I lose connectivity. If I remove the weight command everything works as expected and I am able to connect to the remote sites. My MPLS router is not actually MPLS but just a router running BGP in a different AS number than what I run internally. This is the only thing that is different between the lab and the production equipment that works fine.

Here is a diagram along with the configurations. Thanks.

Bill19795_2 · ‎01-27-2011

Did some more testing today. When I put the weight comand in HQR1 and run some show commands I get

results that are not correct. It appears from the MPLS1 router that HQR1

is advertising routes to the network that RS1R1 has. This must be creating some type of loop but I am only putting the wight command on the HQR1 side.

HQR1

router bgp 65010
no synchronization
bgp log-neighbor-changes
network 12.100.1.0 mask 255.255.255.252
network 192.168.1.0
neighbor 12.100.1.1 remote-as 1000
neighbor 12.100.1.1 allowas-in 2
neighbor 12.100.1.1 weight 40000
no auto-summary

MPLS1

MPLS1#show ip route 192.168.2.0
Routing entry for 192.168.2.0/24
Known via "bgp 1000", distance 20, metric 0
Tag 65010, type external
Last update from 12.100.1.6 00:04:16 ago
Routing Descriptor Blocks:
* 12.100.1.6, from 12.100.1.6, 00:04:16 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 65010

Routing entry for 192.168.1.0/24
Known via "bgp 1000", distance 20, metric 0
Tag 65010, type external
Last update from 12.100.1.2 00:00:20 ago
Routing Descriptor Blocks:
* 12.100.1.2, from 12.100.1.2, 00:00:20 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 65010

MPLS1#show ip bgp 192.168.1.0 255.255.255.0
BGP routing table entry for 192.168.1.0/24, version 5631
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Not advertised to any peer
65010
12.100.1.2 from 12.100.1.2 (192.168.1.253)
Origin IGP, metric 0, localpref 100, valid, external, best
MPLS1#

MPLS1#show ip bgp 192.168.2.0 255.255.255.0
BGP routing table entry for 192.168.2.0/24, version 5
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
        1
65010
    12.100.1.6 from 12.100.1.6 (192.168.2.253)
      Origin IGP, metric 0, localpref 100, valid, external, best
MPLS1#

MPLS1#show ip bgp neighbors 12.100.1.6 advertised-routes
BGP table version is 5645, local router ID is 12.100.1.17
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 12.100.1.0/30    0.0.0.0                  0         32768 i
*> 12.100.1.4/30    0.0.0.0                  0         32768 i
*> 192.168.1.0      12.100.1.2               0             0 65010 i
*> 192.168.2.0      12.100.1.6               0             0 65010 i

Total number of prefixes 3
MPLS1#show ip bgp neighbors 12.100.1.2 advertised-routes
BGP table version is 5643, local router ID is 12.100.1.17
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 12.100.1.0/30    0.0.0.0                  0         32768 i
*> 12.100.1.4/30    0.0.0.0                  0         32768 i
*> 192.168.2.0      12.100.1.6               0             0 65010 i

MPLS1#show ip bgp neighbors 12.100.1.2 advertised-routes
BGP table version is 5643, local router ID is 12.100.1.17
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 12.100.1.0/30    0.0.0.0                  0         32768 i
*> 12.100.1.4/30    0.0.0.0                  0         32768 i
*> 192.168.2.0      12.100.1.6               0             0 65010 i

Bill19795_2 · ‎01-28-2011

Anyone?