Solved: Re: OSPF - BGP redistribution problem

m.lammerse · ‎08-19-2006

Gents,

I have here a connected route, redistributed into OSPF, that is not making it into BGP. Any ideas as to why?

R8#sh ip ospf database external 150.50.4.0

OSPF Router with ID (200.0.0.8) (Process ID 1)

Type-5 AS External Link States

LS age: 1232

Options: (No TOS-capability, DC)

LS Type: AS External Link

Link State ID: 150.x.4.0 (External Network Number )

Advertising Router: 200.0.0.8

LS Seq Number: 80000001

Checksum: 0x7C86

Length: 36

Network Mask: /24

Metric Type: 2 (Larger than any link state path)

TOS: 0

Metric: 20

Forward Address: 0.0.0.0

External Route Tag: 0

R8#

R8 Config :

router bgp 65078

no synchronization

bgp log-neighbor-changes

bgp confederation identifier 200

bgp confederation peers 65256

redistribute ospf 1 match internal external 1 external 2

neighbor 150.x.5.68 remote-as 65078

neighbor 150.x.5.68 next-hop-self

no auto-summary

But no cigar:

R8#sh ip bgp

BGP table version is 3, local router ID is 200.0.0.8

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

*> 8.8.8.0/24 0.0.0.0 0 32768 ?

*> 150.50.5.64/27 0.0.0.0 0 32768 ?

R8#

IOS version:

R8#sh ver

Cisco IOS Software, 2800 Software (C2800NM-ADVENTERPRISEK9-M), Version 12.4(3a), RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Compiled Fri 30-Sep-05 13:24 by hqluong

Configuration:

R8#sh run

Building configuration...

Current configuration : 1704 bytes

!

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

service password-encryption

!

hostname R8

!

boot-start-marker

boot-end-marker

!

enable secret xxx

!

no aaa new-model

!

resource policy

!

memory-size iomem 15

ip subnet-zero

!

ip cef

!

no ip domain lookup

!

interface Loopback0

ip address 200.0.x.x.255.255.255

!

interface Loopback1

ip address 8.8.x.x.255.255.0

ip ospf network point-to-point

!

interface FastEthernet0/0

ip address 150.x.4.x.255.255.0

duplex auto

speed auto

!

interface FastEthernet0/1

no ip address

shutdown

duplex auto

speed auto

!

interface Serial0/0/0

ip address 150.x.5.x.255.255.224

!

router ospf 1

log-adjacency-changes

redistribute connected subnets route-map Conn

network 8.8.8.1 0.0.0.0 area 0

network 150.x.5.x.0.0.0 area 0

!

router bgp 65078

no synchronization

bgp log-neighbor-changes

bgp confederation identifier 200

bgp confederation peers 65256

redistribute ospf 1 match internal external 1 external 2

neighbor 150.50.5.68 remote-as 65078

neighbor 150.x.5.68 next-hop-self

no auto-summary

!

ip classless

!

no ip http server

no ip http secure-server

!

access-list 1 permit 150.x.4.x.0.0.255

!

route-map Conn permit 10

match ip address 1

!

control-plane

!

banner motd ^CC Blah, Blah, Blah... If you are not an authorized user, go away!!! ^C

alias configure sir show ip route

alias configure siib show ip interface brief

!

line con 0

exec-timeout 0 0

password 7 121015120A1B09163E

logging synchronous

line aux 0

line vty 0 4

login

!

warm-reboot

scheduler allocate 20000 1000

!

end

Richard Burts · ‎08-19-2006

Marcel

There are several possible causes. I think that the first one to consider is that the route that you are interested in is a connected route. If you enter the command show ip route and look for the prefix 150.50.4.0 it shows up as a connected route ("C") not OSPF External ("O E2"). When BGP redistributes routes it will be looking in the routing table for routes with an O indicator not a C indicator.

One way to fix this would be to change the BGP config so that it redistributes connected instead of redistributing OSPF. If you use the same route map to control redistribution you would get just the single connected route. Another potential fix is to put a network statement into OSPF for 150.50.4.0 and let it become an OSPF internal route. And perhaps the solution that I would favor would be to put a network statement into BGP for that prefix instead of trying to redistribute.

HTH

Rick

HTH

Rick

View solution in original post

Richard Burts · ‎08-19-2006

Marcel

There are several possible causes. I think that the first one to consider is that the route that you are interested in is a connected route. If you enter the command show ip route and look for the prefix 150.50.4.0 it shows up as a connected route ("C") not OSPF External ("O E2"). When BGP redistributes routes it will be looking in the routing table for routes with an O indicator not a C indicator.

One way to fix this would be to change the BGP config so that it redistributes connected instead of redistributing OSPF. If you use the same route map to control redistribution you would get just the single connected route. Another potential fix is to put a network statement into OSPF for 150.50.4.0 and let it become an OSPF internal route. And perhaps the solution that I would favor would be to put a network statement into BGP for that prefix instead of trying to redistribute.

HTH

Rick

HTH

Rick

m.lammerse · ‎08-19-2006

Hi Rick,

thanks for your quick response. Clear and insightful as always.

I now realize the error of my ways and you are spot on. The specific solution does not matter, it's understanding the mechanism which is what I was after. And you explained it perfectly.

Cheers,

Marcel

Richard Burts · ‎08-19-2006

Marcel

Thank you for rating the post and marking that it did solve your question. It makes the forum more useful when people can read a question and know that an answer was provided which solved it.

And I certainly agree with you that understanding the principles involved is more important that the particular details. And redistribution can be a tricky thing to understand.

HTH

Rick

HTH

Rick