Solved: Re: Stuck on this network

Steven Williams · ‎01-28-2014

Routers 1 - 8 are running IS-IS and they are tag-switching. I can reach all routers loopbacks within the core network.

Now I am peering eBGP with R4 and R7 and I have R4 and R7 peering iBGP. Now from R4 and R7 I can see routes from end to end, but R12 and R9 cannot see each others routes/networks.

I need to redistribute these from R4 and R7 so that R9 and R12 can see them....How can I do this without those routers seeing all the subnets and routes in the core of the network?

Jon Marshall · ‎01-28-2014

Steven

Apologies but i should have said you need to redistribute BGP into IS-IS but not the other way round. This is because the intermediate routers between R4 and R7 need to know about the networks on R9 and R12.

The alternative is to run a full IBGP mesh between every router within your AS or use route reflectors.

Once again sorry i made the same stupid mistake in another thread recently.

Edit - by redistributing BGP into IS-IS you could actually leave synchronization on but you would still have needed to fix the next-hop self issue.

Jon

View solution in original post

Jon Marshall · ‎01-28-2014

Steven

So is R4 peering with R9 via EBGP and the same for R7 to R12 ?

If so, on R4 for one of the networks connected to R12 eg 192.168.12.0/24 when you do a "sh ip bgp 192.168.12.0 255.255.255.0" what is the next hop showing as ?

And if you do a "sh ip route 192.168.12.0 255.255.255.0" on R4 do you see it ?

Jon

Steven Williams · ‎01-28-2014

Yes eBGP peering PE to CE.

iBGP peering PE to PE

This is weird....

R4#show ip bgp
BGP table version is 4, local router ID is 10.10.10.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 172.16.9.0/30    172.16.9.1               0             0 64709 ?
* i172.16.12.0/30   172.16.12.1              0    100      0 64712 ?
*> 192.168.9.0      172.16.9.1               0             0 64709 ?
* i192.168.12.0     172.16.12.1              0    100      0 64712 ?
*> 192.168.99.0     172.16.9.1               0             0 64709 ?
* i192.168.112.0    172.16.12.1              0    100      0 64712 ?
R4#show ip route 192.168.12.1 255.255.255.0
% Network not in table
R4#

I see it in the table?

Steven Williams · ‎01-28-2014

AHHHH but not in the route table.....

R4#show ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
       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    192.168.9.0/24 [20/0] via 172.16.9.1, 00:35:33
     172.16.0.0/30 is subnetted, 1 subnets
C       172.16.9.0 is directly connected, FastEthernet0/0
B    192.168.99.0/24 [20/0] via 172.16.9.1, 00:35:33
     10.0.0.0/8 is variably subnetted, 16 subnets, 2 masks
i L1    10.10.10.8/32 [115/40] via 10.1.1.13, Serial1/0
i L1    10.1.1.8/30 [115/30] via 10.1.1.13, Serial1/0
C       10.1.1.12/30 is directly connected, Serial1/0
i L1    10.10.10.2/32 [115/20] via 10.1.1.13, Serial1/0
i L1    10.10.10.3/32 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.0/30 [115/20] via 10.1.1.13, Serial1/0
i L1    10.10.10.1/32 [115/20] via 10.1.1.13, Serial1/0
i L1    10.10.10.6/32 [115/40] via 10.1.1.13, Serial1/0
i L1    10.10.10.7/32 [115/40] via 10.1.1.13, Serial1/0
i L1    10.1.1.4/30 [115/20] via 10.1.1.13, Serial1/0
C       10.10.10.4/32 is directly connected, Loopback0
i L1    10.10.10.5/32 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.24/30 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.28/30 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.16/30 [115/20] via 10.1.1.13, Serial1/0
i L1    10.1.1.20/30 [115/30] via 10.1.1.13, Serial1/0
R4#

So whats wrong here?

Jon Marshall · ‎01-28-2014

Steven

Add this to R4 -

router bgp

neighbor next-hop self

do the same on R7 and use R4 as the neighbor address.

The issue is when an EBGP peer advertises a route to an IBGP peer the next hop for that route is the remote EBGP peer eg.

R12 advertises 192.168.12.0/24 to R7 ia EBGP. R7 then advertises this to R4 via IBGP with the same next hop. But R4 does not have a route to 172.16.12.1 so it cannot add it to the IP routing table and therefore cannot advertise it to R9.

Using the next-hop self command tells R7 to change the next hop to be itself when it advertises it to R4. R4 knows how to get to R7 so it can install it in the IP routing table and can then advertise it out.

Jon

Steven Williams · ‎01-28-2014

did that, cleared BGP, and no change.

R7#

router bgp 65000

bgp log-neighbor-changes

neighbor 10.10.10.4 remote-as 65000

neighbor 10.10.10.4 update-source Loopback0

neighbor 10.10.10.4 next-hop-self

neighbor 172.16.12.1 remote-as 64712

neighbor 172.16.12.1 update-source FastEthernet0/0

R4#

router bgp 65000

bgp log-neighbor-changes

neighbor 10.10.10.7 remote-as 65000

neighbor 10.10.10.7 update-source Loopback0

neighbor 10.10.10.7 next-hop-self

neighbor 172.16.9.1 remote-as 64709

neighbor 172.16.9.1 update-source FastEthernet0/0

R4#show ip route
Codes: C - connected, S - static, I - IGRP, 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, E - EGP
       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    192.168.9.0/24 [20/0] via 172.16.9.1, 00:02:52
     172.16.0.0/30 is subnetted, 1 subnets
C       172.16.9.0 is directly connected, FastEthernet0/0
B    192.168.99.0/24 [20/0] via 172.16.9.1, 00:02:52
     10.0.0.0/8 is variably subnetted, 16 subnets, 2 masks
i L1    10.10.10.8/32 [115/40] via 10.1.1.13, Serial1/0
i L1    10.1.1.8/30 [115/30] via 10.1.1.13, Serial1/0
C       10.1.1.12/30 is directly connected, Serial1/0
i L1    10.10.10.2/32 [115/20] via 10.1.1.13, Serial1/0
i L1    10.10.10.3/32 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.0/30 [115/20] via 10.1.1.13, Serial1/0
i L1    10.10.10.1/32 [115/20] via 10.1.1.13, Serial1/0
i L1    10.10.10.6/32 [115/40] via 10.1.1.13, Serial1/0
i L1    10.10.10.7/32 [115/40] via 10.1.1.13, Serial1/0
i L1    10.1.1.4/30 [115/20] via 10.1.1.13, Serial1/0
C       10.10.10.4/32 is directly connected, Loopback0
i L1    10.10.10.5/32 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.24/30 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.28/30 [115/30] via 10.1.1.13, Serial1/0
i L1    10.1.1.16/30 [115/20] via 10.1.1.13, Serial1/0
i L1    10.1.1.20/30 [115/30] via 10.1.1.13, Serial1/0
R4#

Jon Marshall · ‎01-28-2014

Can you post "sh ip bgp 192.168.12.0 255.255.255.0" again ?

Jon

Steven Williams · ‎01-28-2014

R4#show ip bgp 192.168.12.0 255.255.255.0
BGP routing table entry for 192.168.12.0/24, version 0
Paths: (1 available, no best path)
Not advertised to any peer
64712
10.10.10.7 (metric 40) from 10.10.10.7 (10.10.10.7)
Origin incomplete, metric 0, localpref 100, valid, internal, not synchronized
R4#

Steven Williams · ‎01-28-2014

Looks R9 isnt seeing anything excepted connected routes? I have configured redistribute connected on both R9 and R12

R9#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

C    192.168.9.0/24 is directly connected, Loopback9
     172.16.0.0/30 is subnetted, 1 subnets
C       172.16.9.0 is directly connected, FastEthernet0/0
C    192.168.99.0/24 is directly connected, Loopback99
R9#show ip bgp
BGP table version is 4, local router ID is 192.168.99.1
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
*> 172.16.9.0/30    0.0.0.0                  0         32768 ?
*> 192.168.9.0      0.0.0.0                  0         32768 ?
*> 192.168.99.0     0.0.0.0                  0         32768 ?
R9#show ip bgp sum
R9#show ip bgp summary
BGP router identifier 192.168.99.1, local AS number 64709
BGP table version is 4, main routing table version 4
3 network entries using 351 bytes of memory
3 path entries using 156 bytes of memory
2/1 BGP path/bestpath attribute entries using 248 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 755 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
172.16.9.2 4 65000 61 63 4 0 0 00:10:44 0
R9#

Jon Marshall · ‎01-28-2014

Steven

I think you have two problems. The first was the one we fixed as this would have stopped it working even without the second problem.

Can you add this to R4 and R7 and retest -

router bgp

no synchronization

Jon

Steven Williams · ‎01-28-2014

Stupid IOS 12.2...old version which required no syn command.

Ok it looks like R4 and R7 are fixed....kinda.

R4#show ip bgp 192.168.12.0 255.255.255.0
BGP routing table entry for 192.168.12.0/24, version 5
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to non peer-group peers:
172.16.9.1
64712
    10.10.10.7 (metric 40) from 10.10.10.7 (10.10.10.7)
      Origin incomplete, metric 0, localpref 100, valid, internal, best
R4#ping 192.168.12.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.12.1, timeout is 2 seconds:
U.U.U
Success rate is 0 percent (0/5)
R4#

R9 and R12 still arent receiving any routes so they dont how to get back.

Steven Williams · ‎01-28-2014

Ok a clear ip bgp * now has R9 and R12 recieving 3 routes prefixes... But how can I do a ping...what do I have to source it from?

R12#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

C    192.168.12.0/24 is directly connected, Loopback12
B    192.168.9.0/24 [20/0] via 172.16.12.2, 00:03:06
     172.16.0.0/30 is subnetted, 2 subnets
C       172.16.12.0 is directly connected, FastEthernet0/0
B       172.16.9.0 [20/0] via 172.16.12.2, 00:03:06
B    192.168.99.0/24 [20/0] via 172.16.12.2, 00:03:06
C    192.168.112.0/24 is directly connected, Loopback112
R12#ping 192.168.9.1 source 172.16.9.26

% Invalid source address- IP address not on any of our up interfaces
R12#show ip int br
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            172.16.12.1     YES NVRAM up                    up
FastEthernet1/0            unassigned      YES NVRAM administratively down down
Loopback12                 192.168.12.1    YES NVRAM up                    up
Loopback112                192.168.112.1   YES NVRAM up                    up
R12#ping 192.168.9.1 source 172.16.12.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.9.1, timeout is 2 seconds:
Packet sent with a source address of 172.16.12.1
.....
Success rate is 0 percent (0/5)
R12#

Steven Williams · ‎01-28-2014

or do I now have redistribute those bgp routes into IS-IS somehow?

Jon Marshall · ‎01-28-2014

Steven

You posted while i was answering. You need to ping with a source IP that R12 has a route for. You do not need any redistribution between IS-IS and BGP.

Edit - my mistake, you do need to redistribute BGP into IS-IS.

Jon

Jon Marshall · ‎01-28-2014

Steven

If you ping from R4 to 192.168.12.1 it will use the 10.1.1.x IP as the source and R12 has no idea how to get to this network.

You need to ping from R9 and use a source IP that R12 has a route for.

R9 and R12 should now be receiving those routes. Are you saying they are not because R4 is showing that route as being advertised to R9 ?

If not can you post a "sh ip bgp 192.168.12.0 255.255.255.0" and a "sh ip route 192.168.12.0" from R9 ?

Jon