Redistributing BGP Confederation learned routes in OSPF

[west33637]

Hello all. When redistributing BGP routes learned from an IBGP confederation peer into OSPF, do I need to enter the bgp redistribute-internal command under the BGP process in order to ensure that BGP allows the routes to get redistributed? or does BGP treat routes learned from confederation peers like ebgp routes for all intents and purposes.

Thanks,
 

[milan.kulik]

Hi,

do you mean a situation like this:

c2811-R1#sh ip bgp
BGP table version is 7, local router ID is 200.1.1.1
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

...

*>i200.8.8.8/32     192.168.20.3             0    100      0 (65002) i
 

c2811-R1#sh run | sec bgp
router bgp 65001
 bgp confederation identifier 200
 bgp confederation peers 65000 65002
 ...

 neighbor 192.168.20.3 remote-as 65001
 

So an iBGP neigbor is advertising a prefix received from other AS within the same confederation.

c2811-R1#sh run | sec ospf
router ospf 1
 redistribute bgp 65001 subnets
 network 192.168.20.0 0.0.0.255 area 0

c2811-R1#sh ip ospf data

            OSPF Router with ID (200.1.1.1) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
200.1.1.1       200.1.1.1       575         0x8000152F 0x002DAA 1

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
10.200.238.0    200.1.1.1       315         0x80000007 0x00C857 0
192.168.11.0    200.1.1.1       575         0x80000007 0x00CD9F 0
c2811-R1#

The prefix 200.8.8.8/32  is not redistributed to OSPF.

After adding

c2811-R1(config)#router bgp 65001
c2811-R1(config-router)#bgp redistribute-internal
 

I can see:

c2811-R1#sh ip ospf data

            OSPF Router with ID (200.1.1.1) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
200.1.1.1       200.1.1.1       660         0x8000152F 0x002DAA 1

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
10.200.238.0    200.1.1.1       400         0x80000007 0x00C857 0
192.168.11.0    200.1.1.1       660         0x80000007 0x00CD9F 0
192.168.22.0    200.1.1.1       34          0x80000001 0x00BF28 0
200.3.3.0       200.1.1.1       34          0x80000001 0x00ECAB 0
200.8.8.8       200.1.1.1       34          0x80000001 0x008B12 65002
c2811-R1#

Now the prefix is redistributed.

Does this answer your question?

Best regards,

Milan

[west33637]

No, this does not answer my question. Im aware about the bgp redistribute-internal command to redistribute iBGP routes into IGP.

My question is whether you need the redistribute-internal command in order to redistribute routes learned from a BGP confederation peer.

To use your example above:

c2811-R1#sh run | sec bgp
router bgp 65001

bgp confederation identifier 200
 bgp confederation peers 65000 65002
neighbor 192.168.20.3 remote-as 65002
 

router ospf 1

redistribute bgp 65001 subnets

[milan.kulik]

Hi,

ok, so here is my lab router config:

router ospf 1
 redistribute bgp 65001 subnets
 network 192.168.20.0 0.0.0.255 area 0
!
router bgp 65001
 bgp confederation identifier 200
 bgp confederation peers 65000 65002
 network 10.200.238.0 mask 255.255.255.0
 neighbor 192.168.11.8 remote-as 65002
!
 

I can see:

c2811-R1#sh ip bgp
...

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.200.238.0/24  0.0.0.0                  0         32768 i
*> 200.8.8.8/32     192.168.11.8             0    100      0 (65002) i
 

And

c2811-R1#sh ip ospf data

            OSPF Router with ID (200.1.1.1) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
200.1.1.1       200.1.1.1       285         0x8000172C 0x002DAB 1

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
10.200.238.0    200.1.1.1       285         0x80000203 0x00CA57 0
200.8.8.8       200.1.1.1       262         0x80000001 0x002CF1 65002
c2811-R1#

So the answer to your question is:

No, you don't need  redistribute-internal command in order to redistribute routes learned from a BGP confederation peer.

Best regards,

Milan