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New Member

BGP Router issue

HI All,

I have set a BGP routing Lab in GNS3  (topology and routers config attached)

Everyting seems to be fine but whenever I shutdown the fa0/1 on Router R2 , R3 is not able to reach R2 networks (15,16,17 networks)

Any help is highly appreciated.

Thanks

Sri

4 REPLIES
Purple

BGP Router issue

Hi,

there is no routing protocol between R2 and R3 so the prefixes are known to R3 via R1 so I don't see how sutting the interface between R2 and R3 can have any influence.

Can you post sh ip route on all routers before shutting then enable debug ip routing on all routers and shut the interface then post the output from the debug as well as sh ip route.

Regards

Alain

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New Member

BGP Router issue

Hi Alain,

I followed the steps what you have suggested. Please find attached logs and let me know if I missed some configuration.

Note :  I did NOT notice any routing changes on R1.

Thank

Sri

------------------------

=~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2013.07.04 14:39:18 =~=~=~=~=~=~=~=~=~=~=~=
            sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     17.0.0.0/21 is subnetted, 1 subnets
D       17.1.0.0 [90/156160] via 100.100.100.2, 00:14:32, FastEthernet0/0
     16.0.0.0/22 is subnetted, 1 subnets
D       16.1.0.0 [90/156160] via 100.100.100.2, 00:14:32, FastEthernet0/0
     100.0.0.0/30 is subnetted, 1 subnets
C       100.100.100.0 is directly connected, FastEthernet0/0
     11.0.0.0/24 is subnetted, 1 subnets
C       11.1.1.0 is directly connected, Loopback0
     12.0.0.0/22 is subnetted, 1 subnets
C       12.1.0.0 is directly connected, Loopback1
     13.0.0.0/21 is subnetted, 1 subnets
C       13.1.0.0 is directly connected, Loopback2
     150.1.0.0/30 is subnetted, 1 subnets
--More--                           C       150.1.1.0 is directly connected, FastEthernet0/1
     15.0.0.0/24 is subnetted, 1 subnets
D       15.1.1.0 [90/156160] via 100.100.100.2, 00:14:42, FastEthernet0/0
R1#debug ip route
R1#debug ip route
                ^
% Invalid input detected at '^' marker.

R1#debug ip route   ing
R1#debug ip routing
IP routing debugging is on
R1#
R1#
R1#
R1#
R1#
R1#
R1#
R1#
R1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     17.0.0.0/21 is subnetted, 1 subnets
D       17.1.0.0 [90/156160] via 100.100.100.2, 00:20:20, FastEthernet0/0
     16.0.0.0/22 is subnetted, 1 subnets
D       16.1.0.0 [90/156160] via 100.100.100.2, 00:20:20, FastEthernet0/0
     100.0.0.0/30 is subnetted, 1 subnets
C       100.100.100.0 is directly connected, FastEthernet0/0
     11.0.0.0/24 is subnetted, 1 subnets
C       11.1.1.0 is directly connected, Loopback0
     12.0.0.0/22 is subnetted, 1 subnets
C       12.1.0.0 is directly connected, Loopback1
     13.0.0.0/21 is subnetted, 1 subnets
C       13.1.0.0 is directly connected, Loopback2
     150.1.0.0/30 is subnetted, 1 subnets
--More--                           C       150.1.1.0 is directly connected, FastEthernet0/1
     15.0.0.0/24 is subnetted, 1 subnets
D       15.1.1.0 [90/156160] via 100.100.100.2, 00:20:33, FastEthernet0/0
R1#    

------------------------------------

=~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2013.07.04 14:41:01 =~=~=~=~=~=~=~=~=~=~=~=
sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     17.0.0.0/21 is subnetted, 1 subnets
C       17.1.0.0 is directly connected, Loopback2
     16.0.0.0/22 is subnetted, 1 subnets
C       16.1.0.0 is directly connected, Loopback1
     100.0.0.0/30 is subnetted, 1 subnets
C       100.100.100.0 is directly connected, FastEthernet0/0
     11.0.0.0/24 is subnetted, 1 subnets
D       11.1.1.0 [90/156160] via 100.100.100.1, 00:15:37, FastEthernet0/0
     12.0.0.0/22 is subnetted, 1 subnets
D       12.1.0.0 [90/156160] via 100.100.100.1, 00:15:37, FastEthernet0/0
     13.0.0.0/21 is subnetted, 1 subnets
D       13.1.0.0 [90/156160] via 100.100.100.1, 00:15:46, FastEthernet0/0
     150.1.0.0/30 is subnetted, 1 subnets
--More--                           C       150.1.1.4 is directly connected, FastEthernet0/1
     15.0.0.0/24 is subnetted, 1 subnets
C       15.1.1.0 is directly connected, Loopback0
R2#debug ip route   ing
R2#debug ip routing
IP routing debugging is on
R2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#int fa0./1         /1
R2(config-if)#sh
R2(config-if)#
*Mar  1 00:17:44.095: RT: is_up: FastEthernet0/1 0 state: 6 sub state: 1 line: 1 has_route: True
*Mar  1 00:17:44.095: RT: interface FastEthernet0/1 removed from routing table
*Mar  1 00:17:44.095: RT: del 150.1.1.4/30 via 0.0.0.0, connected metric [0/0]
*Mar  1 00:17:44.099: RT: delete subnet route to 150.1.1.4/30
*Mar  1 00:17:44.099: RT: NET-RED 150.1.1.4/30
*Mar  1 00:17:44.099: RT: delete network route to 150.1.0.0
*Mar  1 00:17:44.103: RT: NET-RED 150.1.0.0/16
R2(config-if)#
R2(config-if)#
*Mar  1 00:17:44.111: %BGP-5-ADJCHANGE: neighbor 150.1.1.5 Down Interface flap
R2(config-if)#
*Mar  1 00:17:46.087: %LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administratively down
R2(config-if)#
*Mar  1 00:17:46.087: RT: is_up: FastEthernet0/1 0 state: 6 sub state: 1 line: 1 has_route: False
*Mar  1 00:17:47.087: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
R2(config-if)#
*Mar  1 00:17:47.087: RT: is_up: FastEthernet0/1 0 state: 6 sub state: 1 line: 1 has_route: False
R2(config-if)#
R2(config-if)#
R2(config-if)#end
R2#sh ip
*Mar  1 00:19:55.511: %SYS-5-CONFIG_I: Configured from console by console
R2#sh ip bgp sum
BGP router identifier 17.1.1.1, local AS number 200
BGP table version is 8, main routing table version 8
7 network entries using 819 bytes of memory
14 path entries using 728 bytes of memory
5/2 BGP path/bestpath attribute entries using 620 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 2191 total bytes of memory
BGP activity 7/0 prefixes, 14/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
100.100.100.1   4   100      24      24        8    0    0 00:19:06        7
150.1.1.5       4   300      14      16        0    0    0 00:02:15 Idle
R2#sh ip bgp sum
BGP router identifier 17.1.1.1, local AS number 200
BGP table version is 8, main routing table version 8
7 network entries using 819 bytes of memory
14 path entries using 728 bytes of memory
5/2 BGP path/bestpath attribute entries using 620 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 2191 total bytes of memory
BGP activity 7/0 prefixes, 14/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
100.100.100.1   4   100      25      25        8    0    0 00:20:16        7
150.1.1.5       4   300      14      16        0    0    0 00:03:25 Idle
R2#

---------------------------------------------------

=~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2013.07.04 14:41:28 =~=~=~=~=~=~=~=~=~=~=~=
sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     17.0.0.0/21 is subnetted, 1 subnets
B       17.1.0.0 [20/0] via 150.1.1.6, 00:08:25
     16.0.0.0/22 is subnetted, 1 subnets
B       16.1.0.0 [20/0] via 150.1.1.6, 00:08:25
     100.0.0.0/30 is subnetted, 1 subnets
B       100.100.100.0 [20/0] via 150.1.1.6, 00:08:25
     11.0.0.0/24 is subnetted, 1 subnets
B       11.1.1.0 [20/156160] via 150.1.1.6, 00:08:25
     12.0.0.0/22 is subnetted, 1 subnets
B       12.1.0.0 [20/156160] via 150.1.1.6, 00:08:25
     13.0.0.0/21 is subnetted, 1 subnets
B       13.1.0.0 [20/156160] via 150.1.1.6, 00:08:34
     150.1.0.0/30 is subnetted, 2 subnets
--More--                           C       150.1.1.4 is directly connected, FastEthernet0/1
C       150.1.1.0 is directly connected, FastEthernet0/0
     15.0.0.0/24 is subnetted, 1 subnets
B       15.1.1.0 [20/0] via 150.1.1.6, 00:08:36
R3#     debug
R3#     debug ip routing
R3#     debug ip routing
IP routing debugging is on
R3#
R3#
R3#
R3#
*Mar  1 00:20:05.003: %BGP-5-ADJCHANGE: neighbor 150.1.1.6 Down BGP Notification sent
R3#
*Mar  1 00:20:05.003: %BGP-3-NOTIFICATION: sent to neighbor 150.1.1.6 4/0 (hold time expired) 0 bytes
*Mar  1 00:20:06.007: RT: 11.1.1.0/24 gateway changed from 150.1.1.6 to 150.1.1.2
*Mar  1 00:20:06.007: RT: bgp's 11.1.1.0/24 (via 150.1.1.2) metric changed from distance/metric [20/156160] to [20/0]
*Mar  1 00:20:06.007: RT: NET-RED 11.1.1.0/24
*Mar  1 00:20:06.007: RT: 12.1.0.0/22 gateway changed from 150.1.1.6 to 150.1.1.2
*Mar  1 00:20:06.007: RT: bgp's 12.1.0.0/22 (via 150.1.1.2) metric changed from distance/metric [20/156160] to [20/0]
*Mar  1 00:20:06.007: RT: NET-RED 12.1.0.0/22
*Mar  1 00:20:06.007: RT: 13.1.0.0/21 gateway changed from 150.1.1.6 to 150.1.1.2
*Mar  1 00:20:06.007: RT: bgp's 13.1.0.0/21 (via 150.1.1.2) metric changed from distance/metric [20/156160] to [20/0]
*Mar  1 00:20:06.007: RT: NET-RED 13.1.0.0/21
*Mar  1 00:20:06.007: RT: 15.1.1.0/24 gateway changed from 150.1.1.6 to 150.1.1.2
*Mar  1 00:20:06.007: RT: bgp's 15.1.1.0/24 (via 150.1.1.2) metric changed from distance/metric [20/0] to [20/156160]
*Mar  1 00:20:06.007: RT: NET-RED 15.1.1.0/24
*Mar  1 00:20:06.007: RT: 16.1.0.0/22 gateway changed from 150.1.1.6 to 150.1.1.2
*Mar  1 00:20:06.007: RT: bgp's 16.1.0.0/22 (via 150.1.1.2) metric changed from distance/metric [20/0] to [20/156160]
*Mar  1 00:20:06.007: RT: NET-RED 16.1.0.0/22
*Mar  1 00:20:06.007: RT: 17.1.0.0/21 gateway changed from 150.1.1.6 to 150.1.1.2
*Mar  1 00:20:06.007: RT: bgp's 17.1.0.0/21 (via 150.1.1.2) metric changed from distance/metric [20/0] to [20/156160]
*Mar  1 00:20:06.007: RT: NET-RED 17.1.0.0/21
*Mar  1 00:20:06.007: RT: 100.100.100.0/30 gateway changed from 150.1.1.6 to 150.1.1.2
*Mar  1 00:20:06.007: RT: NET-RED 100.100.100.0/30
R3#
R3#
R3#
R3#ship bpg                       ip bgp sum
BGP router identifier 150.1.1.5, local AS number 300
BGP table version is 15, main routing table version 15
7 network entries using 819 bytes of memory
7 path entries using 364 bytes of memory
3/2 BGP path/bestpath attribute entries using 372 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 1579 total bytes of memory
BGP activity 7/0 prefixes, 14/7 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
150.1.1.2       4   100      19      21       15    0    0 00:10:13        7
150.1.1.6       4   200      16      18        0    0    0 00:01:09 Active
R3#

Purple

BGP Router issue

Hi,

in your initial post there was no BGP config in R3 but now there is.

Initially R1 knows these prefixes via EIGRP from R2, they are redistributed into BGP  but in intial config of R1 there is no BGP config with R3 but again this is incorrect information you sent as in the outputs you just provided we see a BGP neighbourship on R3 with R1.So considering this BGP is advertising these prefixes to R3 but R2 which is also redistributing EIGRP into BGP advertises these prefixes to R3 via eBGP too.So only the best path is installed in the routing table and it is from R2 because the AS-PATH is shorter.

Now when you shut the interface on R2 you bring down the BGP neighbourship with R3 and so the other path from R1 becomes the best path( it is the only path now) and these prefixes should be installed as BGP routes with the next-hop of R2(150.1.1.2)

This is what we observe here:

*Mar  1 00:20:06.007: RT: 15.1.1.0/24 gateway changed from 150.1.1.6 to 150.1.1.2

*Mar  1 00:20:06.007: RT: bgp's 15.1.1.0/24 (via 150.1.1.2) metric changed from distance/metric [20/0] to [20/156160]

*Mar  1 00:20:06.007: RT: NET-RED 15.1.1.0/24

*Mar  1 00:20:06.007: RT: 16.1.0.0/22 gateway changed from 150.1.1.6 to 150.1.1.2

*Mar  1 00:20:06.007: RT: bgp's 16.1.0.0/22 (via 150.1.1.2) metric changed from distance/metric [20/0] to [20/156160]

*Mar  1 00:20:06.007: RT: NET-RED 16.1.0.0/22

*Mar  1 00:20:06.007: RT: 17.1.0.0/21 gateway changed from 150.1.1.6 to 150.1.1.2

*Mar  1 00:20:06.007: RT: bgp's 17.1.0.0/21 (via 150.1.1.2) metric changed from distance/metric [20/0] to [20/156160]

*Mar  1 00:20:06.007: RT: NET-RED 17.1.0.0/21

Can you post  sh ip route on R3 to prove this. Now when you ping from R3 to these prefixes your source IP is 150.1.1.1( subnet 150.1.1.0/30) and it seems that R2 doesn't know about this subnet so it can't reply back and that's why you can't communicate with these prefixes on R2.

Just configure a loopback on R3,advertise it with BGP to R1 and R2 and then ping these prefixes with the source interface of this loopback or the source IP of this loopback and everything will work even when R2-R3 goes down.

Regards

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.
New Member

BGP Router issue

are you advertising the 150.1.1.4/30 route anywhere?

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