IBgp issue

[feroz syed]

AS 2 Ibpg  configured with ospf, on Router 3 and Router 5 both ebgp routes appear in route table, but on R4 and R6 there is no Ebgp routes.Goal is need to ping from R1 to R2 loop back address.

R5

R5#sh ip bgp 

BGP table version is 6, 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

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*>i1.1.1.1/32       3.3.3.3                  0    100      0 1 i

*> 2.2.2.2/32       192.168.52.2             0             0 3 i

*>i192.168.13.0     3.3.3.3                  0    100      0 1 i

r> 192.168.52.0     192.168.52.2             0             0 3 i

R5#sh ip route bgp

     1.0.0.0/32 is subnetted, 1 subnets

B       1.1.1.1 [200/0] via 3.3.3.3, 00:26:14

B    192.168.13.0/24 [200/0] via 3.3.3.3, 00:26:14

     2.0.0.0/32 is subnetted, 1 subnets

B       2.2.2.2 [20/0] via 192.168.52.2, 00:26:19

R5#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 2

neighbor 3.3.3.3 update-source Loopback0

neighbor 3.3.3.3 next-hop-self

neighbor 4.4.4.4 remote-as 2

neighbor 4.4.4.4 update-source Loopback0

neighbor 6.6.6.6 remote-as 2

neighbor 6.6.6.6 update-source Loopback0

neighbor 192.168.52.2 remote-as 3

no auto-summary

R3

R3#sh ip bgp

BGP table version is 6, 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

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*> 1.1.1.1/32       192.168.13.1             0             0 1 i

*>i2.2.2.2/32       5.5.5.5                  0    100      0 3 i

r> 192.168.13.0     192.168.13.1             0             0 1 i

*>i192.168.52.0     5.5.5.5                  0    100      0 3 i

R3#sh ip route bgp

     1.0.0.0/32 is subnetted, 1 subnets

B       1.1.1.1 [20/0] via 192.168.13.1, 00:26:47

     2.0.0.0/32 is subnetted, 1 subnets

B       2.2.2.2 [200/0] via 5.5.5.5, 00:26:47

B    192.168.52.0/24 [200/0] via 5.5.5.5, 00:26:47

R3#sh run | sec bp

R3#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 4.4.4.4 remote-as 2

neighbor 4.4.4.4 update-source Loopback0

neighbor 5.5.5.5 remote-as 2

neighbor 5.5.5.5 update-source Loopback0

neighbor 5.5.5.5 next-hop-self

neighbor 6.6.6.6 remote-as 2

neighbor 6.6.6.6 update-source Loopback0

neighbor 192.168.13.1 remote-as 1

no auto-summary

R3#

R4

R4#sh ip bgp

BGP table version is 5, local router ID is 4.4.4.4

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

* i1.1.1.1/32       192.168.13.1             0    100      0 1 i

* i2.2.2.2/32       192.168.52.2             0    100      0 3 i

* i192.168.13.0     192.168.13.1             0    100      0 1 i

* i192.168.52.0     192.168.52.2             0    100      0 3 i

R4#sh ip route bgp

R4#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 2

neighbor 3.3.3.3 update-source Loopback0

neighbor 5.5.5.5 remote-as 2

neighbor 5.5.5.5 update-source Loopback0

neighbor 6.6.6.6 remote-as 2

neighbor 6.6.6.6 update-source Loopback0

no auto-summary

R6#sh ip bgp

BGP table version is 5, local router ID is 6.6.6.6

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

* i1.1.1.1/32       192.168.13.1             0    100      0 1 i

* i2.2.2.2/32       192.168.52.2             0    100      0 3 i

* i192.168.13.0     192.168.13.1             0    100      0 1 i

* i192.168.52.0     192.168.52.2             0    100      0 3 i

R6#sh ip route bgp

R6#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 2

neighbor 3.3.3.3 update-source Loopback0

neighbor 4.4.4.4 remote-as 2

neighbor 4.4.4.4 update-source Loopback0

neighbor 5.5.5.5 remote-as 2

neighbor 5.5.5.5 update-source Loopback0

no auto-summary

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

     1.0.0.0/32 is subnetted, 1 subnets

C       1.1.1.1 is directly connected, Loopback0

C    192.168.13.0/24 is directly connected, Serial1/0

     2.0.0.0/32 is subnetted, 1 subnets

B       2.2.2.2 [20/0] via 192.168.13.3, 00:28:25

B    192.168.52.0/24 [20/0] via 192.168.13.3, 00:28:25

R1#sh ip ngp

          ^

% Invalid input detected at '^' marker.

R1#sh ip bgp

BGP table version is 5, 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

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*> 1.1.1.1/32       0.0.0.0                  0         32768 i

*> 2.2.2.2/32       192.168.13.3                           0 2 3 i

*> 192.168.13.0     0.0.0.0                  0         32768 i

*> 192.168.52.0     192.168.13.3                           0 2 3 i

R1#sh run | sec bgp

router bgp 1

no synchronization

bgp log-neighbor-changes

network 1.1.1.1 mask 255.255.255.255

network 192.168.13.0

neighbor 192.168.13.3 remote-as 2

no auto-summary

R2

R2#sh ip bgp

BGP table version is 5, local router ID is 2.2.2.2

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

*> 1.1.1.1/32       192.168.52.5                           0 2 1 i

*> 2.2.2.2/32       0.0.0.0                  0         32768 i

*> 192.168.13.0     192.168.52.5                           0 2 1 i

*> 192.168.52.0     0.0.0.0                  0         32768 i

R2#sh ip route bgp

     1.0.0.0/32 is subnetted, 1 subnets

B       1.1.1.1 [20/0] via 192.168.52.5, 00:29:29

B    192.168.13.0/24 [20/0] via 192.168.52.5, 00:29:29

R2#sh run | sec bgp

router bgp 3

no synchronization

bgp log-neighbor-changes

network 2.2.2.2 mask 255.255.255.255

network 192.168.52.0

neighbor 192.168.52.5 remote-as 2

no auto-summary

[Jon Marshall]

If you do a "sh ip route" on R4 is there is route for 192.168.52.2 ?

It looks like the same problem as before. R4 may have entry in it's BGP table for 192.168.52.2 but it needs it in the IP routing table.

So if that route is not in the IP routing table on R4 and R6 add the "next-hop self" command to R3 and R5 for their peerings with R4 and R6.

Jon

[feroz syed]

0kay now i have bgp routes in R4 and R6 but still not able to ping 1.1.1.1 or 2.2.2.2

R6#sh ip route bgp

     1.0.0.0/32 is subnetted, 1 subnets

B       1.1.1.1 [200/0] via 3.3.3.3, 00:07:59

B    192.168.13.0/24 [200/0] via 3.3.3.3, 00:07:59

     2.0.0.0/32 is subnetted, 1 subnets

B       2.2.2.2 [200/0] via 5.5.5.5, 00:08:38

B    192.168.52.0/24 [200/0] via 5.5.5.5, 00:08:38

R6#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 2

neighbor 3.3.3.3 update-source Loopback0

neighbor 3.3.3.3 next-hop-self

neighbor 4.4.4.4 remote-as 2

neighbor 5.5.5.5 remote-as 2

neighbor 5.5.5.5 update-source Loopback0

neighbor 5.5.5.5 next-hop-self

no auto-summary

[Jon Marshall]

When you ping from R4 or R6 the source IP will 192.168.45/65.x respecitvely but R2 does not have routes in it's IP routing table for these subnets.

If you want to be able to ping from R4/R6 you would need to advertise those subnets to R2. You can do this with -

1)   "network ..." commands on R5 under the BGP configuration

or

2) a "redistribute connected" under the BGP configuration on R5

Jon

[feroz syed]

Okay, if remove bgp from  R4 and R6, can we able to ping from As 1 to As 3 using R5 and R3 ?

[cadet alain]

Hi,

In this case you'll have to redistribute those specific BGP routes into your IGP or run MPLS in your core.

Regards

Alain

Don't forget to rate helpful posts.

[feroz syed]

If i do so, it will receive lot of prefix from bgp to ospf, and ospf not going handle 350k + prefix

[Jon Marshall]

You do not need to redistribute BGP into OSPF because you have an IBGP peering between R3 and R5. OSPF in your setup is simply used to provide reachability between R3 and R5.

So as long as you use the "next-hop self" command you should be fine.

Bear in mind that when you had IBGP on R4/R6 any routes received by R5 from R2 were advertised to R3, R4 and R6 but R4 and R6 did then not advertise the same routes to R3.

This is because an IBGP router that learns a route from an IBGP peer cannot then advertise it to another IBGP peer. Your setup worked because you also had an IBGP peering between R3 and R5 even though it actually went via R4 or R6 ie. there is no direct link between R3 and R5.

You can overcome the IBGP issue with a full mesh ie. every IBGP router peers with every other IBGP router whether over direct links or indirect links although direct are better or you can use route reflectors.

Jon

[cadet alain · Accepted solution]

Hi Jon,

if only  r3 and r5 are BGP peers in AS2 then the middle routers will be blackholing the traffic  because they don't know about the BGP routes  from external ASes.

Regards

Alain

Don't forget to rate helpful posts.

[Jon Marshall]

Hi Alain

You are completely correct, my mistake.

Thanks for correcting.

Jon

[Jon Marshall]

Alain

I'm must remember to save this post for when there is yet another discussion about ratings in the social forums and everyone (except myself and Rick) argues for removing the lower marks.

It's posts like the one above that should actually get that rating because it's just basic routing.

Once again, thanks for stepping in and clearing things up

Jon

[cadet alain]

Hi Jon,

I don't mind about ratings so much as to ask the deletion of 1 or 2 marks but sometimes we solve problems(whether they are basic or not is just a point of view and what is basic for me may not be for the poster) and we only get 1-2 marks then indeed it is disappointing but this is very rare and my first objective here is not points even if my signature could be interpreted in another way 

By the way thanks for the +5 

Regards

Alain

Don't forget to rate helpful posts.

[cadet alain]

Hi,

If i do so, it will receive lot of prefix from bgp to ospf, and ospf not going handle 350k + prefix 

that's why I said:

In this case you'll have to redistribute those specific BGP routes into your IGP or run MPLS in your core.

Using a route-map.

Regards

Alain

Don't forget to rate helpful posts.

[paul driver]

Hello

Alain - As I see it you dont need to to redistribute bgp into ospf-

As long as the IBGP "core* has  a full mesh with synchronization turned off and full NRLI via ospf  then all should be fine- and R1=R2 should be able to reach each other via their loopbacks

Would be nice to see the IGP config for routers R3-6

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

[cadet alain]

Hi Paul,

If there is no BGP on the middle routers then how wil they know about the BGP prefixes unless we redistribute or use static routes ?

Regards

Alain

Don't forget to rate helpful posts.