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Beginner

Redistributing BGP aggregated routes int OSPF

Aloha,

 

I ran into a issue at work, and labbed it to see where is the error. 

 

Router 1 and Router 2 are sending BGP aggregated routes into Router 3

Router 1 is sending 10.200.10.0/24 Router 2 is sending 10.200.20.0/24

Router 3 redistributes all BGP routes into Router 4 via OSPF

Router 4 receives the aggregated routes via OSPF and redistributes into Router 5 via BGP

However I do not see the routes being sent out to router 5 using soft-configuration from R4 and I obviously do not see Router 5 receiving the aggregated routes via the soft-configuration command from R4

 

I can ping everything behind Router 1 and Router 2 from Router 4, however, can't ping from R5 to R1 or R2

 

Is this a bug on GNS3? The configuration looks good to me. I think there is an issue redistributing BGP sourced aggregated routes into OSPF? Because when I remove the redistribution from R4 to R5, R5 looses all its redistrubuted learned routes from R4. So this indicates that redistribution seems to be working correctly. Seems like only the aggregated routes is not being redistributed.

 

R4 routing configuration:

 

router ospf 100

 log-adjacency-changes

 redistribute bgp 80 subnets

 passive-interface default

 no passive-interface GigabitEthernet0/0

 network 10.200.70.0 0.0.0.3 area 0

 network 10.200.80.10 0.0.0.0 area 0

 network 10.200.80.20 0.0.0.0 area 0

router bgp 80

 no synchronization

 bgp log-neighbor-changes

 network 10.200.80.30 mask 255.255.255.255

 network 172.17.1.0 mask 255.255.255.252

 redistribute ospf 100

 neighbor 172.17.1.255 remote-as 100

 neighbor 172.17.1.255 description ASB-EDGE

 neighbor 172.17.1.255 ebgp-multihop 2

 neighbor 172.17.1.255 soft-reconfiguration inbound

 no auto-summary

 

Router 4 ip route table

 

   172.17.0.0/16 is variably subnetted, 7 subnets, 2 masks

S       172.17.1.255/32 [1/0] via 172.17.1.2

B       172.17.1.40/32 [20/0] via 172.17.1.255, 00:30:59

B       172.17.1.30/32 [20/0] via 172.17.1.255, 00:30:59

B       172.17.1.20/32 [20/0] via 172.17.1.255, 00:30:59

B       172.17.1.10/32 [20/0] via 172.17.1.255, 00:30:59

C       172.17.1.0/30 is directly connected, GigabitEthernet1/0

B       172.17.2.0/30 [20/0] via 172.17.1.255, 00:30:59

     10.0.0.0/8 is variably subnetted, 16 subnets, 3 masks

C       10.200.70.0/30 is directly connected, GigabitEthernet0/0

C       10.200.80.20/32 is directly connected, Loopback20

C       10.200.80.30/32 is directly connected, Loopback30

C       10.200.80.10/32 is directly connected, Loopback10

O E2    10.200.50.70/32 [110/1] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O       10.200.50.50/32 [110/3] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O E2    10.200.10.0/30 [110/1] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O E2    10.200.10.0/24 [110/1] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O       10.200.60.40/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O E2    10.200.20.0/30 [110/1] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O E2    10.200.20.0/24 [110/1] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O       10.200.60.30/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O       10.200.60.20/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O       10.200.50.0/30 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O       10.200.60.10/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

O       10.200.60.0/30 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

 

Router 4 BGP table

 

   Network          Next Hop            Metric LocPrf Weight Path

*> 10.200.50.0/30   10.200.70.2              2         32768 ?

*> 10.200.50.50/32  10.200.70.2              3         32768 ?

*> 10.200.60.0/30   10.200.70.2              2         32768 ?

*> 10.200.60.10/32  10.200.70.2              2         32768 ?

*> 10.200.60.20/32  10.200.70.2              2         32768 ?

*> 10.200.60.30/32  10.200.70.2              2         32768 ?

*> 10.200.60.40/32  10.200.70.2              2         32768 ?

*> 10.200.70.0/30   0.0.0.0                  0         32768 ?

*> 10.200.80.10/32  0.0.0.0                  0         32768 ?

*> 10.200.80.20/32  0.0.0.0                  0         32768 ?

*> 10.200.80.30/32  0.0.0.0                  0         32768 i

*> 172.17.1.0/30    0.0.0.0                  0         32768 i

*> 172.17.1.10/32   172.17.1.255             0             0 100 ?

*> 172.17.1.20/32   172.17.1.255             0             0 100 ?

*> 172.17.1.30/32   172.17.1.255             0             0 100 i

*> 172.17.1.40/32   172.17.1.255             0             0 100 i

*> 172.17.2.0/30    172.17.1.255             0             0 100 ?

 

 

Router 5 routing configuration:

 

router bgp 100

 no synchronization

 bgp log-neighbor-changes

 network 172.17.1.0 mask 255.255.255.255

 network 172.17.1.30 mask 255.255.255.255

 network 172.17.1.40 mask 255.255.255.255

 redistribute eigrp 200

 neighbor 172.17.1.1 remote-as 80

 neighbor 172.17.1.1 description HT-ASB-PE

 neighbor 172.17.1.1 soft-reconfiguration inbound

 no auto-summary

 

Router 5 routing table 

 

Gateway of last resort is not set

 

     172.17.0.0/16 is variably subnetted, 7 subnets, 2 masks

C       172.17.1.255/32 is directly connected, Loopback100

C       172.17.1.40/32 is directly connected, Loopback40

C       172.17.1.30/32 is directly connected, Loopback30

C       172.17.1.20/32 is directly connected, Loopback20

C       172.17.1.10/32 is directly connected, Loopback10

C       172.17.1.0/30 is directly connected, FastEthernet0/0

C       172.17.2.0/30 is directly connected, FastEthernet0/1

     10.0.0.0/8 is variably subnetted, 11 subnets, 2 masks

B       10.200.70.0/30 [20/0] via 172.17.1.1, 00:11:22

B       10.200.80.20/32 [20/0] via 172.17.1.1, 00:11:22

B       10.200.80.30/32 [20/0] via 172.17.1.1, 00:26:34

B       10.200.80.10/32 [20/0] via 172.17.1.1, 00:11:22

B       10.200.50.50/32 [20/3] via 172.17.1.1, 00:11:22

B       10.200.60.40/32 [20/2] via 172.17.1.1, 00:11:22

B       10.200.60.30/32 [20/2] via 172.17.1.1, 00:11:22

B       10.200.60.20/32 [20/2] via 172.17.1.1, 00:11:22

B       10.200.50.0/30 [20/2] via 172.17.1.1, 00:11:22

B       10.200.60.10/32 [20/2] via 172.17.1.1, 00:11:22

B       10.200.60.0/30 [20/2] via 172.17.1.1, 00:11:22

 

Router 5 BGP table

 

   Network          Next Hop            Metric LocPrf Weight Path

*> 10.200.50.0/30   172.17.1.1               2             0 80 ?

*> 10.200.50.50/32  172.17.1.1               3             0 80 ?

*> 10.200.60.0/30   172.17.1.1               2             0 80 ?

*> 10.200.60.10/32  172.17.1.1               2             0 80 ?

*> 10.200.60.20/32  172.17.1.1               2             0 80 ?

*> 10.200.60.30/32  172.17.1.1               2             0 80 ?

*> 10.200.60.40/32  172.17.1.1               2             0 80 ?

*> 10.200.70.0/30   172.17.1.1               0             0 80 ?

*> 10.200.80.10/32  172.17.1.1               0             0 80 ?

*> 10.200.80.20/32  172.17.1.1               0             0 80 ?

*> 10.200.80.30/32  172.17.1.1               0             0 80 i

r> 172.17.1.0/30    172.17.1.1               0             0 80 i

*> 172.17.1.10/32   0.0.0.0                  0         32768 ?

*> 172.17.1.20/32   0.0.0.0                  0         32768 ?

*> 172.17.1.30/32   0.0.0.0                  0         32768 i

*> 172.17.1.40/32   0.0.0.0                  0         32768 i

*> 172.17.2.0/30    0.0.0.0                  0         32768 ?

2 ACCEPTED SOLUTIONS

Accepted Solutions
VIP Mentor

Re: Redistributing BGP aggregated routes int OSPF

Hello,

 

not sure if this is a bug, what if you specifically configure:

 

R4

 

redistribute ospf 100 match internal external 1 external 2

Beginner

Re: Redistributing BGP aggregated routes int OSPF

This is what I found online:

IOS will not redistribute OSPF external information into BGP by default (internal only). You need to apply the 'match internal external' switch to your redistribute statement to get this to work.
11 REPLIES 11
VIP Mentor

Re: Redistributing BGP aggregated routes int OSPF

Hello,

 

not sure if this is a bug, what if you specifically configure:

 

R4

 

redistribute ospf 100 match internal external 1 external 2

Beginner

Re: Redistributing BGP aggregated routes int OSPF

Wow! That worked. Strange. Is this a bug, or must this be configured in order to redistribute BGP sourced aggregated routes?
Beginner

Re: Redistributing BGP aggregated routes int OSPF

Wow! That worked. Strange. Is this a bug, or must this be configured in order to redistribute BGP sourced aggregated routes?
VIP Mentor

Re: Redistributing BGP aggregated routes int OSPF

Hello,

 

in theory, without the keywords, only OSPF intra-area and inter-area routes should have been redistributed into BGP. So you shoud get at least the 'O' routes.

 

Which IOS are you running this on in GNS3 ?

Beginner

Re: Redistributing BGP aggregated routes int OSPF

BOOTLDR: 7200 Software (C7200-ADVIPSERVICESK9-M), Version 12.4(24)T8, RELEASE SOFTWARE (fc1)

Prob IOS bug?? The only way I know of to run good up-to date IOS images, is by spinning up a VM. Ugh! I dont have resources for that.
VIP Mentor

Re: Redistributing BGP aggregated routes int OSPF

Hello,

 

I am testing with 15.6(2)T...will let you know...

Beginner

Re: Redistributing BGP aggregated routes int OSPF

This is what I found online:

IOS will not redistribute OSPF external information into BGP by default (internal only). You need to apply the 'match internal external' switch to your redistribute statement to get this to work.
VIP Mentor

Re: Redistributing BGP aggregated routes int OSPF

Exactly. So by default you get only the 'O' and 'O-IA' routes (the latter you don't have')...

VIP Mentor

Re: Redistributing BGP aggregated routes int OSPF

Hello,

 

it works as designed in 15(6)2T.

 

Actually, looking at the routing table of your R4 router and the routing table of your R5 router, I think all the redistributed 'O' routes are there ?

 

O 10.200.50.50/32 [110/3] via 10.200.70.2, 00:31:25, GigabitEthernet0/0
O 10.200.60.40/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0
O 10.200.60.30/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0
O 10.200.60.20/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0
O 10.200.50.0/30 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0
O 10.200.60.10/32 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0
O 10.200.60.0/30 [110/2] via 10.200.70.2, 00:31:25, GigabitEthernet0/0

 

B 10.200.70.0/30 [20/0] via 172.17.1.1, 00:11:22
B 10.200.80.20/32 [20/0] via 172.17.1.1, 00:11:22
B 10.200.80.30/32 [20/0] via 172.17.1.1, 00:26:34
B 10.200.80.10/32 [20/0] via 172.17.1.1, 00:11:22
B 10.200.50.50/32 [20/3] via 172.17.1.1, 00:11:22
B 10.200.60.40/32 [20/2] via 172.17.1.1, 00:11:22
B 10.200.60.30/32 [20/2] via 172.17.1.1, 00:11:22
B 10.200.60.20/32 [20/2] via 172.17.1.1, 00:11:22
B 10.200.50.0/30 [20/2] via 172.17.1.1, 00:11:22
B 10.200.60.10/32 [20/2] via 172.17.1.1, 00:11:22
B 10.200.60.0/30 [20/2] via 172.17.1.1, 00:11:22

Beginner

Re: Redistributing BGP aggregated routes int OSPF

Yes. This is new to me since a lot of clients network I manage runs EIGRP versus OSPF. Knowledge added to the bucket. Thanks for your help Georg!
Beginner

Re: Redistributing BGP aggregated routes int OSPF

btw is this a OSPF flaw, BGP flaw, or by design?
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