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DaeHeon Kang
Beginner

OSPF routes in database but not in routing table

I have been looking for the reason why R4 doesn't show R1 and R2 loopback IP addresses on the routing table. The R1 & R2 loopback IP addresses are seen on the OSPF datebase as Router Link State on the R4.

However, It shows it's unreachable when checked those loopback IP addresses by command, show ip ospf datebase router 1.1.1.1 or 2.2.2.2.  Interestingly, The problem was solved when I changed the OSPF network type between R2 and R3 from broadcast to point to point. 

OSPF routing.jpg

11 REPLIES 11
omz
VIP Collaborator VIP Collaborator
VIP Collaborator

Loopbacks are considered host routes in OSPF, and they are advertised as /32.

If the ip ospf network point-to-point command is configured under loopbacks OSPF advertises the loopback subnet as the actual subnet configured on loopbacks.

 

This is not about ospf network type under loobpback interfaces. There are no any command ospf network type point to point on the all looback interfaces. 

paul driver
VIP Mentor

Hello

Really shouldn't make any difference -  Were this rtr's all in the same area, Was it is possible the interfaces between r2-r3 were in a ospf  state other than full or the loopbacks interfaces were disabled



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future

The ospf broadcast type is only the link betwwen R2-R3 as there is no any ospf network type configuration.

And also there are no ip ospf network type point to point command under all loopback interfaces.

 

All routers are in thw same area 0 and all routers including R4 show loopback addresses of each router as router link state on OSPF database. The weird thing is only R4 doesn’t show R1 and R2 loopback addrsses on the routing table.

Hello 

that is indeed strange - did or can you by any chance clear the ospf process of all 4 rtrs?

Can your reach R1/2 physical interfaces from R4?

 



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future

Sorry this problems has been solved by put ospf netwok type point to point on the link between R2-R3. And this is the production network which is hard to try to make the duplicate issue.

it’s really weird m. I haven’t seen this kind of thing before. Even I was considering about ios bug..

omz
VIP Collaborator VIP Collaborator
VIP Collaborator

If the state of the interface is Loopback, add a Type 3
link (stub network) as long as this is not an interface
to an unnumbered point-to-point network.  The Link ID
should be set to the IP interface address, the Link Data
set to the mask 0xffffffff (indicating a host route),
and the cost set to 0.

RFC2328 

Hello

@omz

This will just show the route are a host route even if the loopback address isnt a host address, However it shouldnt negate it being advertised and entering the rib



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
omz
VIP Collaborator VIP Collaborator
VIP Collaborator

@paul driver That's absolutely right Paul

 

R1#sh run int lo0 | b int
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
 ip ospf network point-to-point
end

R2#sh run int lo0 | b int
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
end

R3#sh run int lo0 | b int
interface Loopback0
 ip address 3.3.3.3 255.255.255.0
end

R4#sh run int lo0 | b int
interface Loopback0
 ip address 4.4.4.4 255.255.255.255
end

R2#sh ip rou | i 1.0.0.0|1.1
      1.0.0.0/24 is subnetted, 1 subnets
O        1.1.1.0 [110/11] via 10.10.12.1, 00:00:05, Ethernet0/0
R2#sh ip rou | i 4.0.0.0|4.4
      4.0.0.0/32 is subnetted, 1 subnets
O        4.4.4.4 [110/21] via 10.10.23.3, 00:00:05, Ethernet0/1
R2#sh ip rou | i 3.0.0.0|_3.3
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/11] via 10.10.23.3, 00:14:48, Ethernet0/1 R1#sh ip ospf int lo0 | i Type Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1 R1# R1#sh ip ospf int e0/0 | i Type Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10 R1# R2#sh ip ospf int lo0 | i Type Process ID 1, Router ID 2.2.2.2, Network Type LOOPBACK, Cost: 1 R2# R1#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/6 ms R1#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/6 ms R1#ping 4.4.4.4 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/3 ms R1# R2#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/6 ms R2#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/7 ms R2#ping 4.4.4.4 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/6 ms R2# R3#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/7 ms R3#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/5 ms R3#ping 4.4.4.4 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/5 ms R3# R4#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 2/4/6 ms R4#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/5 ms R4#ping 3.3.3.3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/5 ms R4#

R1 lo 0 configured with /24 and network type point-to-point

R4 lo 0 configured with /32 

No connectivity issues between the routers

You cannot change the loopback network type to broadcast 

There are no any ospf point to point network type command under all router’s loopback interfaces. All routers show /32 for each loopback address. This problem seems narrowing down about the ospf network type between R2-R3 as it was solved or happened depend on the network type of the link.