Routes Not Advertised Through EBGP

[tigerpaws]

Hello,

I have a question that I hope someone can help.  For some reason, I cannot ping the networks behind MGGS1-RR1 from the Core-RT and vice versa.  When I issued the "show ip route" command on MGGS1-RR1, I only saw the two directly connected networks on the routing table.  It looks like its routes are not advertised on the neighbor router, NRR1.  I would appreciate it if someone could point to where the missing step(s) is/are.  Please refer to the configuration files and the diagram below:

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

hostname Core-RT
!
interface Loopback0
 description "Core Router Loopback IP Address"
 ip address 1.1.1.1 255.255.255.255
 ip ospf 100 area 0
!
interface Ethernet0/0
 description "Link to RSW1"
 ip address 10.10.10.1 255.255.255.0
 ip ospf 100 area 0
!
router ospf 100
 router-id 1.1.1.1
!
router bgp 400
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 redistribute connected
 neighbor 10.10.30.2 remote-as 400
 neighbor 10.10.30.2 update-source Ethernet0/0
!
Core-RT#

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

hostname RSW
!
interface Loopback0
 description "RSW Loopback IP Address"
 ip address 4.4.4.4 255.255.255.255
 ip ospf 100 area 0
!
interface Ethernet0/0
 description "Link to Core Router Ethernet0/0"
 no switchport
 ip address 10.10.10.2 255.255.255.0
 ip ospf 100 area 0
!
interface Ethernet0/1
 description "Link to RR #1 Ethernet0/0"
 no switchport
 ip address 10.10.30.1 255.255.255.0
 ip ospf 100 area 0
!
router ospf 100
 router-id 4.4.4.4

!

RSW#

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

hostname RR1
!
interface Loopback0
 description "RR#1 Loopback IP Address"
 ip address 2.2.2.2 255.255.255.255
 ip ospf 100 area 0
!
interface Ethernet0/1
 description "Link to RSW"
 ip address 10.10.30.2 255.255.255.0
 ip ospf 100 area 0
!
interface Ethernet1/0
 description "Link to NRR1"
 ip address 10.10.20.2 255.255.255.0
!
router ospf 100
 router-id 2.2.2.2
 redistribute bgp 400 subnets
!
router bgp 400
 bgp router-id 2.2.2.2
 bgp log-neighbor-changes
 bgp redistribute-internal
 network 2.2.2.2 mask 255.255.255.255
 network 10.10.20.0 mask 255.255.255.0
 redistribute ospf 100 route-map OSPF-To-BGP
 neighbor 10.10.10.1 remote-as 400
 neighbor 10.10.10.1 update-source Ethernet0/1
 neighbor 10.10.10.1 next-hop-self
 neighbor 10.10.20.1 remote-as 300
 neighbor 10.10.20.1 ebgp-multihop 2
 neighbor 10.10.20.1 update-source Ethernet1/0
 neighbor 10.10.20.1 next-hop-self
!
route-map OSPF-To-BGP permit 10
 match ip address 1
 set metric 150
 set tag 10
!
access-list 1 permit 1.1.1.1 log
access-list 1 permit 4.4.4.4 log
access-list 1 permit 10.10.10.0 0.0.0.255 log
access-list 1 permit 10.10.30.0 0.0.0.255 log
access-list 1 deny   any log
!
end

RR1#

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

hostname NRR1
!
interface Loopback0
 description "NRR1 Loopback IP Address"
 ip address 3.3.3.3 255.255.255.255
!
interface Ethernet0/0
 description "Link to MGGS1 - RR1"
 ip address 10.10.40.2 255.255.255.0
!
interface Ethernet1/0
 description "Link to RR1"
 ip address 10.10.20.1 255.255.255.0
!
router bgp 300
 bgp router-id 3.3.3.3
 bgp log-neighbor-changes
 network 3.3.3.3 mask 255.255.255.255
 network 10.10.20.0 mask 255.255.255.0
 network 10.10.40.0 mask 255.255.255.0
 neighbor 10.10.20.2 remote-as 400
 neighbor 10.10.20.2 ebgp-multihop 2
 neighbor 10.10.20.2 update-source Ethernet1/0
 neighbor 10.10.40.1 remote-as 400
 neighbor 10.10.40.1 ebgp-multihop 2
 neighbor 10.10.40.1 update-source Ethernet0/0
!
end

NRR1#

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

hostname MGGS1-RR1
!
interface Loopback0
 description "MGGS-1 - RR1 Loopback IP Address"
 ip address 5.5.5.5 255.255.255.255
!
interface Ethernet0/0
 description "Link to RR1"
 ip address 10.10.40.1 255.255.255.0
!
router bgp 400
 bgp router-id 5.5.5.5
 bgp log-neighbor-changes
 network 5.5.5.5 mask 255.255.255.255
 neighbor 10.10.40.2 remote-as 300
 neighbor 10.10.40.2 ebgp-multihop 2
 neighbor 10.10.40.2 update-source Ethernet0/0
!
end

MGGS1-RR1#

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

+ Output from show commands:

Core-RT#sho ip bgp summary

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.10.30.2      4          400     278     274       19    0    0 04:03:40        8
Core-RT#

Core-RT#sho ip bgp

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.1/32       0.0.0.0                  0         32768 ?
 * i                  10.10.30.2             150    100      0 ?
 r>i 2.2.2.2/32       10.10.30.2               0    100      0 i
 r>i 3.3.3.3/32       10.10.30.2               0    100      0 300 i
 r>i 4.4.4.4/32       10.10.30.2             150    100      0 ?
 *>  10.10.10.0/24    0.0.0.0                  0         32768 ?
 * i                  10.10.30.2             150    100      0 ?
 r>i 10.10.20.0/24    10.10.30.2               0    100      0 i
 r>i 10.10.30.0/24    10.10.30.2             150    100      0 ?
 r>i 10.10.40.0/24    10.10.30.2               0    100      0 300 i

Core-RT#sho ip route

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
C        1.1.1.1 is directly connected, Loopback0
      2.0.0.0/32 is subnetted, 1 subnets
O        2.2.2.2 [110/21] via 10.10.10.2, 20:39:37, Ethernet0/0
      3.0.0.0/32 is subnetted, 1 subnets
O E2     3.3.3.3 [110/1] via 10.10.10.2, 03:57:03, Ethernet0/0
      4.0.0.0/32 is subnetted, 1 subnets
O        4.4.4.4 [110/11] via 10.10.10.2, 20:41:13, Ethernet0/0
      10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C        10.10.10.0/24 is directly connected, Ethernet0/0
L        10.10.10.1/32 is directly connected, Ethernet0/0
O E2     10.10.20.0/24 [110/1] via 10.10.10.2, 20:28:03, Ethernet0/0
O        10.10.30.0/24 [110/20] via 10.10.10.2, 20:41:13, Ethernet0/0
O E2     10.10.40.0/24 [110/1] via 10.10.10.2, 03:57:03, Ethernet0/0
Core-RT#

RSW#sho ip ospf neigh

Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   FULL/DR         00:00:37    10.10.10.1      Ethernet0/0
2.2.2.2           1   FULL/BDR        00:00:32    10.10.30.2      Ethernet0/1

RSW#sho ip route

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
O        1.1.1.1 [110/11] via 10.10.10.1, 20:42:23, Ethernet0/0
      2.0.0.0/32 is subnetted, 1 subnets
O        2.2.2.2 [110/11] via 10.10.30.2, 20:40:43, Ethernet0/1
      3.0.0.0/32 is subnetted, 1 subnets
O E2     3.3.3.3 [110/1] via 10.10.30.2, 03:58:09, Ethernet0/1
      4.0.0.0/32 is subnetted, 1 subnets
C        4.4.4.4 is directly connected, Loopback0
      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C        10.10.10.0/24 is directly connected, Ethernet0/0
L        10.10.10.2/32 is directly connected, Ethernet0/0
O E2     10.10.20.0/24 [110/1] via 10.10.30.2, 20:29:10, Ethernet0/1
C        10.10.30.0/24 is directly connected, Ethernet0/1
L        10.10.30.1/32 is directly connected, Ethernet0/1
O E2     10.10.40.0/24 [110/1] via 10.10.30.2, 03:58:09, Ethernet0/1

RR1#sho ip bgp summary

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.10.10.1      4          400     270     273       11    0    0 03:59:31        2
10.10.20.1      4          300     281     269       11    0    0 03:59:38        3

RR1#sho ip bgp

     Network          Next Hop            Metric LocPrf Weight Path
 * i 1.1.1.1/32       10.10.10.1               0    100      0 ?
 *>                   10.10.30.1             150         32768 ?
 *>  2.2.2.2/32       0.0.0.0                  0         32768 i
 *>  3.3.3.3/32       10.10.20.1               0             0 300 i
 *>  4.4.4.4/32       10.10.30.1             150         32768 ?
 * i 10.10.10.0/24    10.10.10.1               0    100      0 ?
 *>                   10.10.30.1             150         32768 ?
 *>  10.10.20.0/24    0.0.0.0                  0         32768 i
 *                    10.10.20.1               0             0 300 i
 *>  10.10.30.0/24    0.0.0.0                150         32768 ?
 *>  10.10.40.0/24    10.10.20.1               0             0 300 i

RR1#sho ip route

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
O        1.1.1.1 [110/21] via 10.10.30.1, 20:41:20, Ethernet0/1
      2.0.0.0/32 is subnetted, 1 subnets
C        2.2.2.2 is directly connected, Loopback0
      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [20/0] via 10.10.20.1, 03:58:49
      4.0.0.0/32 is subnetted, 1 subnets
O        4.4.4.4 [110/11] via 10.10.30.1, 20:41:20, Ethernet0/1
      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
O        10.10.10.0/24 [110/20] via 10.10.30.1, 20:41:20, Ethernet0/1
C        10.10.20.0/24 is directly connected, Ethernet1/0
L        10.10.20.2/32 is directly connected, Ethernet1/0
C        10.10.30.0/24 is directly connected, Ethernet0/1
L        10.10.30.2/32 is directly connected, Ethernet0/1
B        10.10.40.0/24 [20/0] via 10.10.20.1, 03:58:49

NRR1#sho ip bgp summary

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.10.20.2      4          400     270     282       28    0    0 04:00:35        6
10.10.40.1      4          400     280     291       28    0    0 04:00:41        1

NRR1#sho ip bgp

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.1/32       10.10.20.2             150             0 400 ?
 *>  2.2.2.2/32       10.10.20.2               0             0 400 i
 *>  3.3.3.3/32       0.0.0.0                  0         32768 i
 *>  4.4.4.4/32       10.10.20.2             150             0 400 ?
 *>  5.5.5.5/32       10.10.40.1               0             0 400 i
 *>  10.10.10.0/24    10.10.20.2             150             0 400 ?
 *   10.10.20.0/24    10.10.20.2               0             0 400 i
 *>                   0.0.0.0                  0         32768 i
 *>  10.10.30.0/24    10.10.20.2             150             0 400 ?
 *>  10.10.40.0/24    0.0.0.0                  0         32768 i

NRR1#sho ip route

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
B        1.1.1.1 [20/150] via 10.10.20.2, 03:29:44
      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [20/0] via 10.10.20.2, 03:29:44
      3.0.0.0/32 is subnetted, 1 subnets
C        3.3.3.3 is directly connected, Loopback0
      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [20/150] via 10.10.20.2, 03:29:44
      5.0.0.0/32 is subnetted, 1 subnets
B        5.5.5.5 [20/0] via 10.10.40.1, 03:29:44
      10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
B        10.10.10.0/24 [20/150] via 10.10.20.2, 03:29:44
C        10.10.20.0/24 is directly connected, Ethernet1/0
L        10.10.20.1/32 is directly connected, Ethernet1/0
B        10.10.30.0/24 [20/150] via 10.10.20.2, 03:29:44
C        10.10.40.0/24 is directly connected, Ethernet0/0
L        10.10.40.2/32 is directly connected, Ethernet0/0
C        10.10.100.0/24 is directly connected, Ethernet0/1
L        10.10.100.2/32 is directly connected, Ethernet0/1

MGGS1-RR1#sho ip bgp summary

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.10.40.2      4          300     292     281       14    0    0 04:01:32        3

MGGS1-RR1#sho ip bgp

     Network          Next Hop            Metric LocPrf Weight Path
 *>  3.3.3.3/32       10.10.40.2               0             0 300 i
 *>  5.5.5.5/32       0.0.0.0                  0         32768 i
 *>  10.10.20.0/24    10.10.40.2               0             0 300 i
 r>  10.10.40.0/24    10.10.40.2               0             0 300 i

MGGS1-RR1#sho ip route

Gateway of last resort is not set

      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [20/0] via 10.10.40.2, 01:08:18
      5.0.0.0/32 is subnetted, 1 subnets
C        5.5.5.5 is directly connected, Loopback0
      10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
B        10.10.20.0/24 [20/0] via 10.10.40.2, 01:08:18
C        10.10.40.0/24 is directly connected, Ethernet0/0
L        10.10.40.1/32 is directly connected, Ethernet0/0

Thank you in advance.

[Dennis Mink]

your 1.1.1.1 route exists on NRR1. so the problem seems to be between NRR1 and MSGC-RR1

if you do sh bgp nei 10.10.40.1 advertised-routes on NRR1 does it actually advertise its routes out to MSG-RR1?

[tigerpaws]

Hi Mink,

Please see the output from the show command that you suggested.

NRR1#sho ip bgp neighbors 10.10.40.1 advertised-routes
BGP table version is 22, local router ID is 3.3.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.1/32       10.10.40.1                             0 400 ?
 *>  2.2.2.2/32       10.10.20.2               0             0 400 i
 *>  3.3.3.3/32       0.0.0.0                  0         32768 i
 *>  4.4.4.4/32       10.10.20.2             150             0 400 ?
 *>  5.5.5.5/32       10.10.40.1               0             0 400 i
 *>  10.10.10.0/24    10.10.40.1                             0 400 ?
 *>  10.10.20.0/24    0.0.0.0                  0         32768 i
 *>  10.10.30.0/24    10.10.20.2             150             0 400 ?
 *>  10.10.40.0/24    0.0.0.0                  0         32768 i

Total number of prefixes 9
NRR1#

[tigerpaws]

Hello Mink,

The output provided earlier was generated after I inserted the static route into MGGS1-RR1 as follows:

ip route 10.10.10.0 255.255.255.0 10.10.40.2

I really want the routes to learn through BGP and not static routes.  Is there a way to do that?

Thanks

[Dennis Mink]

Yes you shouldnt need to use static routes when you have BGP, you can but its not a requirement.

is the BGP neighbour ship between your mscg-rr1 and nrr1 established at all?

[cofee · Accepted solution]

Hi,

I am not sure about this static route and why would you need it, but you don't have any static routes in your first post and you don't need any.

The reason you don't have connectivity to 5.5.5.5 from Core RT or RR1 because they are in the AS 400 and 5.5.5.5 also originates from AS 400, this is a loop prevention mechanism used by BGP, when a BGP speaking router receives a prefix that includes it's own AS in the AS PATH it won't accept it. So MGGS1-RR1 won't accept any prefix advertised by Core RT or RR1 and vice versa.

There are two ways to resolve this issue and I am sharing the one that I used:

On RR1 use this command:
 router bgp 400

neighbor 10.10.20.1 allowas-in

On MGGS1-RR1 use this command:

router bgp 400

neighbor 10.10.40.2 allowas-in

- After making all these changes I was able to ping 5.5.5.5 from loop back 0 of core RT

Core-RT#ping 5.5.5.5 source loop 0 repeat 1000
Type escape sequence to abort.
Sending 1000, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (1000/1000), round-trip min/avg/max = 44/125/172 ms

Core-RT#sh ip bgp
BGP table version is 57, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external, f RT-Filter
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
* i1.1.1.1/32       10.10.30.2             150    100      0 ?
*>                  0.0.0.0                  0         32768 ?
r>i2.2.2.2/32       10.10.30.2               0    100      0 i
r>i3.3.3.3/32       10.10.30.2               0    100      0 300 i
r>i4.4.4.4/32       10.10.30.2             150    100      0 ?
r>i5.5.5.5/32       10.10.30.2               0    100      0 300 400 i
* i10.10.10.0/24    10.10.30.2             150    100      0 ?
*>                  0.0.0.0                  0         32768 ?
r>i10.10.20.0/24    10.10.30.2               0    100      0 i
r>i10.10.30.0/24    10.10.30.2             150    100      0 ?
r>i10.10.40.0/24    10.10.30.2               0    100      0 300 i

MGGS1-RR1#sh ip bgp
BGP table version is 14, local router ID is 5.5.5.5
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external, f RT-Filter
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 1.1.1.1/32       10.10.40.2                             0 300 400 ?
*> 2.2.2.2/32       10.10.40.2                             0 300 400 i
*> 3.3.3.3/32       10.10.40.2               0             0 300 i
*> 4.4.4.4/32       10.10.40.2                             0 300 400 ?
*  5.5.5.5/32       10.10.40.2                             0 300 400 i
*>                  0.0.0.0                  0         32768 i
*> 10.10.10.0/24    10.10.40.2                             0 300 400 ?
*> 10.10.20.0/24    10.10.40.2               0             0 300 i
*> 10.10.30.0/24    10.10.40.2                             0 300 400 ?
r> 10.10.40.0/24    10.10.40.2               0             0 300 i

- BGP rib failure is occurring in AS 400 because you are learning loopback address from ospf which has AD of 110 vs iBGP AD of 200, nothing to do with static routes. Also you don't need to use to ebgp-multihop command since you are peering using directly connected interfaces and neighbor is only 1 hop away anyways and also the update source because by default it will use the directly connected interface.

[tigerpaws]

You rock!!!  I am able to ping back and forth after adding the recommended changes and removing the unnecessary lines in the BGP configuration files.  I am truly amazed by the knowledge and expert advices from this Support Group.

Thank you very much for your help coffee...