BGP:I do next-hop-self, but getting 'network unreachable'

Unanswered Question
Nov 30th, 2009
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Hi, I am testing BGP peer-group in the lab and so far I can't figure out why from R3 I can't ping host on network 112.0.0.0.

Please find attached my troubleshooting rationale in red. I'd appreciate if you can help me find what I am missing. Thanks again in advance.



Rack4R3#
Rack4R3#ping 112.0.0.1 source lo 0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 112.0.0.1, timeout is 2 seconds:
Packet sent with a source address of 150.4.3.3
U.U.U
Success rate is 0 percent (0/5)
Rack4R3#show ip bgp
BGP table version is 80, local router ID is 150.4.3.3
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
*>i28.119.16.0/24   150.4.4.4                0    100      0 54 i
*>i28.119.17.0/24   150.4.4.4                0    100      0 54 i
*>i112.0.0.0        150.4.4.4                0    100      0 54 50 60 i <= I see next hop is R4 (150.4.4.4). Before going to R4, I go to peer-group R1 and see if I can ping 112.0.0.1 from there.
*>i113.0.0.0        150.4.4.4                0    100      0 54 50 60 i
*>i114.0.0.0        150.4.4.4                0    100      0 54 i
*>i115.0.0.0        150.4.4.4                0    100      0 54 i
*>i116.0.0.0        150.4.4.4                0    100      0 54 i
*>i117.0.0.0        150.4.4.4                0    100      0 54 i
*>i118.0.0.0        150.4.4.4                0    100      0 54 i
*>i119.0.0.0        150.4.4.4                0    100      0 54 i
r>i150.4.1.0/24     150.4.1.1                0    100      0 i
*> 150.4.3.0/24     0.0.0.0                  0         32768 i
r>i150.4.4.0/24     150.4.4.4                0    100      0 i
r>i150.4.5.0/24     150.4.5.5                0    100      0 i
r>i150.4.6.0/24     150.4.6.6                0    100      0 i
Rack4R3#
RSRack4AS>1
[Resuming connection 1 to R1 ... ]

Rack4R1#show ip bgp
BGP table version is 80, local router ID is 150.4.1.1
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
*>i28.119.16.0/24   150.4.4.4                0    100      0 54 i
* i                 150.4.6.6                0    100      0 54 i
*>i28.119.17.0/24   150.4.4.4                0    100      0 54 i
* i                 150.4.6.6                0    100      0 54 i
*>i112.0.0.0        150.4.4.4                0    100      0 54 50 60 i <== This points to R4. It is expected to me.
* i                 150.4.6.6                0    100      0 54 50 60 i
*>i113.0.0.0        150.4.4.4                0    100      0 54 50 60 i
* i                 150.4.6.6                0    100      0 54 50 60 i
*>i114.0.0.0        150.4.4.4                0    100      0 54 i
* i                 150.4.6.6                0    100      0 54 i
*>i115.0.0.0        150.4.4.4                0    100      0 54 i
* i                 150.4.6.6                0    100      0 54 i
*>i116.0.0.0        150.4.4.4                0    100      0 54 i
* i                 150.4.6.6                0    100      0 54 i
*>i117.0.0.0        150.4.4.4                0    100      0 54 i
* i                 150.4.6.6                0    100      0 54 i
*>i118.0.0.0        150.4.4.4                0    100      0 54 i

Rack4R1#
Rack4R1#ping 112.0.0.1 source lo 0                           <====== I confirm that R1 can ping 112.0.0.1 OK

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 112.0.0.1, timeout is 2 seconds:
Packet sent with a source address of 150.4.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/33/36 ms

Rack4R1#show run | s bgp
router bgp 100
no synchronization
bgp log-neighbor-changes
network 150.4.1.0 mask 255.255.255.0
neighbor IBGP_PEERS peer-group
neighbor IBGP_PEERS remote-as 100
neighbor IBGP_PEERS update-source Loopback0
neighbor IBGP_PEERS route-reflector-client
neighbor 150.4.3.3 peer-group IBGP_PEERS  < ==== It correctly makes R3 as a peer-group member. So I can't see where the failure is.
neighbor 150.4.4.4 peer-group IBGP_PEERS
neighbor 150.4.5.5 peer-group IBGP_PEERS
neighbor 150.4.6.6 peer-group IBGP_PEERS
no auto-summary
Rack4R1#


RSRack4AS>4
[Resuming connection 4 to R4 ... ]

Rack4R4#ping 112.0.0.1 source lo 0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 112.0.0.1, timeout is 2 seconds:      <=== I can ping just OK from R4. What is expected since R1 could ping too.
Packet sent with a source address of 150.4.4.4
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/32/36 ms
Rack4R4#show ip bgp
BGP table version is 20, local router ID is 150.4.4.4
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
*> 28.119.16.0/24   204.12.4.254             0             0 54 i
*> 28.119.17.0/24   204.12.4.254             0             0 54 i
*> 112.0.0.0        204.12.4.254                           0 54 50 60 i            <=== This makes sense to me.
*> 113.0.0.0        204.12.4.254                           0 54 50 60 i
*> 114.0.0.0        204.12.4.254                           0 54 i
*> 115.0.0.0        204.12.4.254                           0 54 i
*> 116.0.0.0        204.12.4.254                           0 54 i
*> 117.0.0.0        204.12.4.254                           0 54 i
*> 118.0.0.0        204.12.4.254                           0 54 i
*> 119.0.0.0        204.12.4.254                           0 54 i
r>i150.4.1.0/24     150.4.1.1                0    100      0 i
r>i150.4.3.0/24     150.4.3.3                0    100      0 i
*> 150.4.4.0/24     0.0.0.0                  0         32768 i
r>i150.4.5.0/24     150.4.5.5                0    100      0 i
r>i150.4.6.0/24     150.4.6.6                0    100      0 i
Rack4R4#show run | s bgp
router bgp 100
no synchronization
bgp log-neighbor-changes
network 150.4.4.0 mask 255.255.255.0
neighbor 150.4.1.1 remote-as 100
neighbor 150.4.1.1 update-source Loopback0
neighbor 150.4.1.1 next-hop-self            <== This is the loopback0 of R1. It is correct.
neighbor 204.12.4.254 remote-as 54
no auto-summary
Rack4R4#
RSRack4AS>6
[Resuming connection 6 to R6 ... ]

Rack4R6#show ip bgp
BGP table version is 25, local router ID is 150.4.6.6
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
* i28.119.16.0/24   150.4.4.4                0    100      0 54 i
*>                  54.4.1.254                             0 54 i
* i28.119.17.0/24   150.4.4.4                0    100      0 54 i
*>                  54.4.1.254                             0 54 i
* i112.0.0.0        150.4.4.4                0    100      0 54 50 60 i
*>                  54.4.1.254               0             0 54 50 60 i
* i113.0.0.0        150.4.4.4                0    100      0 54 50 60 i
*>                  54.4.1.254               0             0 54 50 60 i
* i114.0.0.0        150.4.4.4                0    100      0 54 i
*>                  54.4.1.254               0             0 54 i
* i115.0.0.0        150.4.4.4                0    100      0 54 i
*>                  54.4.1.254               0             0 54 i
* i116.0.0.0        150.4.4.4                0    100      0 54 i
*>                  54.4.1.254               0             0 54 i
* i117.0.0.0        150.4.4.4                0    100      0 54 i
*>                  54.4.1.254               0             0 54 i
* i118.0.0.0        150.4.4.4                0    100      0 54 i

Rack4R6#
Rack4R6#ping 112.0.0.1 source lo 0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 112.0.0.1, timeout is 2 seconds:
Packet sent with a source address of 150.4.6.6
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/33/36 ms
Rack4R6#show run | s bgp
router bgp 100
no synchronization
bgp log-neighbor-changes
network 150.4.6.0 mask 255.255.255.0
neighbor 54.4.1.254 remote-as 54
neighbor 150.4.1.1 remote-as 100
neighbor 150.4.1.1 update-source Loopback0
neighbor 150.4.1.1 next-hop-self <== This is correct too. It points to R1.
no auto-summary
Rack4R6#
RSRack4AS>4
[Resuming connection 4 to R4 ... ]

Rack4R4#3

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Jon Marshall Mon, 11/30/2009 - 14:11
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Marlon


Can you post routing tables from R1 and R3 ?


Jon

news2010a Mon, 11/30/2009 - 14:31
User Badges:

Sure. Here it is:


Rack4R1#   show 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

B    119.0.0.0/8 [200/0] via 150.4.4.4, 00:50:29
B    118.0.0.0/8 [200/0] via 150.4.4.4, 00:50:29
B    117.0.0.0/8 [200/0] via 150.4.4.4, 00:50:29
     155.4.0.0/24 is subnetted, 15 subnets
C       155.4.146.0 is directly connected, FastEthernet0/0
D       155.4.23.0 [90/3193856] via 155.4.0.5, 02:12:54, Serial0/0.1
C       155.4.13.0 is directly connected, Serial0/1
D       155.4.10.0 [90/2175232] via 155.4.0.5, 02:12:54, Serial0/0.1
D       155.4.9.0 [90/31232] via 155.4.146.6, 02:12:54, FastEthernet0/0
D       155.4.8.0 [90/2172672] via 155.4.0.5, 02:12:55, Serial0/0.1
D       155.4.7.0 [90/30976] via 155.4.146.6, 02:12:55, FastEthernet0/0
D       155.4.5.0 [90/2172416] via 155.4.0.5, 02:12:55, Serial0/0.1
C       155.4.0.0 is directly connected, Serial0/0.1
D       155.4.58.0 [90/2172416] via 155.4.0.5, 02:12:56, Serial0/0.1
D       155.4.45.0 [90/2172416] via 155.4.146.4, 02:12:53, FastEthernet0/0
D       155.4.37.0 [90/33280] via 155.4.146.6, 02:12:56, FastEthernet0/0
D       155.4.79.0 [90/30976] via 155.4.146.6, 02:12:56, FastEthernet0/0
D       155.4.67.0 [90/30720] via 155.4.146.6, 02:12:56, FastEthernet0/0
D       155.4.108.0 [90/2174976] via 155.4.0.5, 02:12:56, Serial0/0.1
B    116.0.0.0/8 [200/0] via 150.4.4.4, 00:50:31
B    115.0.0.0/8 [200/0] via 150.4.4.4, 00:50:31
B    114.0.0.0/8 [200/0] via 150.4.4.4, 00:50:31
B    113.0.0.0/8 [200/0] via 150.4.4.4, 00:50:31
B    112.0.0.0/8 [200/0] via 150.4.4.4, 00:50:31
     28.0.0.0/24 is subnetted, 2 subnets
B       28.119.17.0 [200/0] via 150.4.4.4, 00:50:31
B       28.119.16.0 [200/0] via 150.4.4.4, 00:50:31
     150.4.0.0/24 is subnetted, 5 subnets
D       150.4.3.0 [90/161280] via 155.4.146.6, 02:00:38, FastEthernet0/0
C       150.4.1.0 is directly connected, Loopback0
D       150.4.6.0 [90/156160] via 155.4.146.6, 01:57:34, FastEthernet0/0
D       150.4.4.0 [90/156160] via 155.4.146.4, 01:59:32, FastEthernet0/0
D       150.4.5.0 [90/2297856] via 155.4.0.5, 01:58:49, Serial0/0.1
Rack4R1#
RSRack4AS#3
% 3 is not an open connection
RSRack4AS#r3
Trying R3 (1.1.1.1, 2003)... Open

Rack4R3#sho 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

B    119.0.0.0/8 [200/0] via 150.4.4.4, 00:50:42
B    118.0.0.0/8 [200/0] via 150.4.4.4, 00:50:42
B    117.0.0.0/8 [200/0] via 150.4.4.4, 00:50:42
     155.4.0.0/24 is subnetted, 15 subnets
D       155.4.146.0 [90/30976] via 155.4.37.7, 02:13:10, FastEthernet0/0
C       155.4.23.0 is directly connected, Serial1/3
C       155.4.13.0 is directly connected, Serial1/2
D       155.4.10.0 [90/2180608] via 155.4.37.7, 02:13:07, FastEthernet0/0
D       155.4.9.0 [90/28672] via 155.4.37.7, 02:13:07, FastEthernet0/0
D       155.4.8.0 [90/2178048] via 155.4.37.7, 02:13:09, FastEthernet0/0
D       155.4.7.0 [90/28416] via 155.4.37.7, 02:13:09, FastEthernet0/0
D       155.4.5.0 [90/2177792] via 155.4.37.7, 02:13:09, FastEthernet0/0
C       155.4.0.0 is directly connected, Serial1/0.1
D       155.4.58.0 [90/2177792] via 155.4.37.7, 02:13:10, FastEthernet0/0
D       155.4.45.0 [90/2175232] via 155.4.37.7, 02:13:07, FastEthernet0/0
C       155.4.37.0 is directly connected, FastEthernet0/0
D       155.4.79.0 [90/28416] via 155.4.37.7, 02:13:10, FastEthernet0/0
D       155.4.67.0 [90/28416] via 155.4.37.7, 02:13:10, FastEthernet0/0
D       155.4.108.0 [90/2180352] via 155.4.37.7, 02:13:10, FastEthernet0/0
B    116.0.0.0/8 [200/0] via 150.4.4.4, 00:50:44
B    115.0.0.0/8 [200/0] via 150.4.4.4, 00:50:44
B    114.0.0.0/8 [200/0] via 150.4.4.4, 00:50:44
B    113.0.0.0/8 [200/0] via 150.4.4.4, 00:50:44
B    112.0.0.0/8 [200/0] via 150.4.4.4, 00:50:44
     28.0.0.0/24 is subnetted, 2 subnets
B       28.119.17.0 [200/0] via 150.4.4.4, 00:50:44
B       28.119.16.0 [200/0] via 150.4.4.4, 00:50:44
     150.4.0.0/24 is subnetted, 5 subnets
C       150.4.3.0 is directly connected, Loopback0
D       150.4.1.0 [90/158976] via 155.4.37.7, 02:01:54, FastEthernet0/0
D       150.4.6.0 [90/156416] via 155.4.37.7, 01:57:48, FastEthernet0/0
D       150.4.4.0 [90/158976] via 155.4.37.7, 01:59:46, FastEthernet0/0
D       150.4.5.0 [90/2303232] via 155.4.37.7, 01:59:02, FastEthernet0/0
Rack4R3#
RSRack4AS#r4
Trying R4 (1.1.1.1, 2004)... Open

Rack4R4#show 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

B    119.0.0.0/8 [20/0] via 204.12.4.254, 00:51:05
B    118.0.0.0/8 [20/0] via 204.12.4.254, 00:51:05
B    117.0.0.0/8 [20/0] via 204.12.4.254, 00:51:05
     155.4.0.0/24 is subnetted, 15 subnets
C       155.4.146.0 is directly connected, FastEthernet0/1
D       155.4.23.0 [90/3193856] via 155.4.45.5, 02:13:28, Serial0/1/0
                   [90/3193856] via 155.4.0.5, 02:13:28, Serial0/0/0.1
D       155.4.13.0 [90/2172416] via 155.4.146.1, 02:13:28, FastEthernet0/1
D       155.4.10.0 [90/2175232] via 155.4.45.5, 02:13:28, Serial0/1/0
                   [90/2175232] via 155.4.0.5, 02:13:28, Serial0/0/0.1
D       155.4.9.0 [90/31232] via 155.4.146.6, 02:13:31, FastEthernet0/1
D       155.4.8.0 [90/2172672] via 155.4.45.5, 02:13:28, Serial0/1/0
                  [90/2172672] via 155.4.0.5, 02:13:28, Serial0/0/0.1
D       155.4.7.0 [90/30976] via 155.4.146.6, 02:13:33, FastEthernet0/1
D       155.4.5.0 [90/2172416] via 155.4.45.5, 02:13:30, Serial0/1/0
                  [90/2172416] via 155.4.0.5, 02:13:30, Serial0/0/0.1
C       155.4.0.0 is directly connected, Serial0/0/0.1
D       155.4.58.0 [90/2172416] via 155.4.45.5, 02:13:31, Serial0/1/0
                   [90/2172416] via 155.4.0.5, 02:13:31, Serial0/0/0.1
C       155.4.45.0 is directly connected, Serial0/1/0
D       155.4.37.0 [90/33280] via 155.4.146.6, 02:13:34, FastEthernet0/1
D       155.4.79.0 [90/30976] via 155.4.146.6, 02:13:34, FastEthernet0/1
D       155.4.67.0 [90/30720] via 155.4.146.6, 02:13:34, FastEthernet0/1
D       155.4.108.0 [90/2174976] via 155.4.45.5, 02:13:31, Serial0/1/0
                    [90/2174976] via 155.4.0.5, 02:13:31, Serial0/0/0.1
B    116.0.0.0/8 [20/0] via 204.12.4.254, 00:51:08
B    115.0.0.0/8 [20/0] via 204.12.4.254, 00:51:08
C    204.12.4.0/24 is directly connected, FastEthernet0/0
B    114.0.0.0/8 [20/0] via 204.12.4.254, 00:51:08
B    113.0.0.0/8 [20/0] via 204.12.4.254, 00:51:08
B    112.0.0.0/8 [20/0] via 204.12.4.254, 00:51:08
     28.0.0.0/24 is subnetted, 2 subnets
B       28.119.17.0 [20/0] via 204.12.4.254, 00:51:08
B       28.119.16.0 [20/0] via 204.12.4.254, 00:51:08
     150.4.0.0/24 is subnetted, 5 subnets
D       150.4.3.0 [90/161280] via 155.4.146.6, 02:01:15, FastEthernet0/1
D       150.4.1.0 [90/156160] via 155.4.146.1, 02:02:18, FastEthernet0/1
D       150.4.6.0 [90/156160] via 155.4.146.6, 01:58:11, FastEthernet0/1
C       150.4.4.0 is directly connected, Loopback0
D       150.4.5.0 [90/2297856] via 155.4.45.5, 01:59:27, Serial0/1/0
                  [90/2297856] via 155.4.0.5, 01:59:27, Serial0/0/0.1
Rack4R4#
RSRack4AS#6
% 6 is not an open connection
RSRack4AS#
RSRack4AS#r6
Trying R6 (1.1.1.1, 2006)... Open

Rack4R6#show 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

B    119.0.0.0/8 [20/0] via 54.4.1.254, 00:55:16
B    118.0.0.0/8 [20/0] via 54.4.1.254, 00:55:16
B    117.0.0.0/8 [20/0] via 54.4.1.254, 00:55:16
     155.4.0.0/24 is subnetted, 15 subnets
C       155.4.146.0 is directly connected, FastEthernet0/0.146
D       155.4.23.0 [90/3196416] via 155.4.146.4, 02:13:43, FastEthernet0/0.146
                   [90/3196416] via 155.4.146.1, 02:13:43, FastEthernet0/0.146
D       155.4.13.0 [90/2172416] via 155.4.146.1, 02:13:46, FastEthernet0/0.146
D       155.4.10.0 [90/2177792] via 155.4.146.4, 02:13:43, FastEthernet0/0.146
                   [90/2177792] via 155.4.146.1, 02:13:43, FastEthernet0/0.146
D       155.4.9.0 [90/28672] via 155.4.67.7, 02:13:46, FastEthernet0/0.67
D       155.4.8.0 [90/2175232] via 155.4.146.4, 02:13:43, FastEthernet0/0.146
                  [90/2175232] via 155.4.146.1, 02:13:43, FastEthernet0/0.146
D       155.4.7.0 [90/28416] via 155.4.67.7, 02:13:48, FastEthernet0/0.67
D       155.4.5.0 [90/2174976] via 155.4.146.4, 02:13:45, FastEthernet0/0.146
                  [90/2174976] via 155.4.146.1, 02:13:45, FastEthernet0/0.146
D       155.4.0.0 [90/2172416] via 155.4.146.4, 02:13:45, FastEthernet0/0.146
                  [90/2172416] via 155.4.146.1, 02:13:45, FastEthernet0/0.146
D       155.4.58.0 [90/2174976] via 155.4.146.4, 02:13:45, FastEthernet0/0.146
                   [90/2174976] via 155.4.146.1, 02:13:45, FastEthernet0/0.146
D       155.4.45.0 [90/2172416] via 155.4.146.4, 02:13:45, FastEthernet0/0.146
D       155.4.37.0 [90/30720] via 155.4.67.7, 02:13:48, FastEthernet0/0.67
D       155.4.79.0 [90/28416] via 155.4.67.7, 02:13:48, FastEthernet0/0.67
C       155.4.67.0 is directly connected, FastEthernet0/0.67
D       155.4.108.0
           [90/2177536] via 155.4.146.4, 02:13:45, FastEthernet0/0.146
           [90/2177536] via 155.4.146.1, 02:13:45, FastEthernet0/0.146
B    116.0.0.0/8 [20/0] via 54.4.1.254, 00:55:18
B    115.0.0.0/8 [20/0] via 54.4.1.254, 00:55:18
B    114.0.0.0/8 [20/0] via 54.4.1.254, 00:55:18
     54.0.0.0/24 is subnetted, 1 subnets
C       54.4.1.0 is directly connected, Serial0/0/0
B    113.0.0.0/8 [20/0] via 54.4.1.254, 00:55:18
B    112.0.0.0/8 [20/0] via 54.4.1.254, 00:55:18
     28.0.0.0/24 is subnetted, 2 subnets
B       28.119.17.0 [20/0] via 54.4.1.254, 00:55:18
B       28.119.16.0 [20/0] via 54.4.1.254, 00:55:19
     150.4.0.0/24 is subnetted, 5 subnets
D       150.4.3.0 [90/158720] via 155.4.67.7, 02:01:30, FastEthernet0/0.67
D       150.4.1.0 [90/156160] via 155.4.146.1, 02:02:32, FastEthernet0/0.146
C       150.4.6.0 is directly connected, Loopback0
D       150.4.4.0 [90/156160] via 155.4.146.4, 02:00:23, FastEthernet0/0.146
D       150.4.5.0 [90/2300416] via 155.4.146.4, 01:59:40, FastEthernet0/0.146
                  [90/2300416] via 155.4.146.1, 01:59:40, FastEthernet0/0.146
Rack4R6#

marikakis Mon, 11/30/2009 - 16:42
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  • Gold, 750 points or more

When troubleshooting routing issues have the following in mind:
1. Use "sh ip route", instead of "sh ip bgp" to determine the path that packets actually take. A route isn't necessarily installed by BGP. Could be from IGP or anything.
2. Observe the mask of the routes carefully.
3. Start the following procedure from R3
a. "sh ip route 112.0.0.1" => via
b. telnet to and repeat "sh ip route 112.0.0.1" => via
c. if reached originating router or edge router learning route from external connection, start tracing back the source IP of the ping  (150.4.3.3) from there, following a similar procedure, and you should be going back to R3, else there is a broken path or loop.
4. Use "traceroute" instead of "ping". Ping doesn't help troubleshoot routing issues. When it fails you don't know where the problem is, and when it succeeds you don't know the path actually taken (with trace you still don't know the return path, but you can sometimes trace in the opposite direction to overcome that). If previous procedure at 3 seemed confusing, you could trace from R3 to quickly view at which hop problems start. Similarly, you could go to R4 and trace towards the source.


I think there is a problem in the return path towards 150.4.3.3. Please see the following output:


R3
B    112.0.0.0/8 [200/0] via 150.4.4.4, 00:50:44


R4
B    112.0.0.0/8 [20/0] via 204.12.4.254, 00:51:08
C    204.12.4.0/24 is directly connected, FastEthernet0/0
D    150.4.3.0 [90/161280] via 155.4.146.6, 02:01:15, FastEthernet0/1


R6
D    150.4.3.0 [90/158720] via 155.4.67.7, 02:01:30, FastEthernet0/0.67


Should R4 be sending packets for 150.4.3.0 to 155.4.146.6?
R4 does receive BGP route to 150.4.3.0/24 from R3, but doesn't install it because some EIGRP router seems to know better. 
r>i150.4.3.0/24     150.4.3.3                0    100      0 i


Should R6 be sending packets for 150.4.3.0 to 155.4.67.7? Which router is 155.4.67.7?

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