OSPF database question

[tinhnho123]

Hello guys,

I have 3 x layer 3 switches which named A, B and C. The switch A is connected to B and C (B and C don't connect each other).

I made a mistake on switch B, under its ospf network statement  I had  'network 10.10.10.2/32 area 0' instead of 'network 10.10.10.1/32 area 0'. I had corrected it yesterday but from switch C I still can't ping 10.10.10.1 of VLAN 10 which on switch B.

.

Below are current configuration of 3 switches:

Switch B:

interface vlan 10
 ip 10.10.10.1 255.255.255.0
 no shut

interface e1/1
 ip address 172.20.1.1/30
 no shut

interface loopback 0
 ip add 10.10.255.1/32

router ospf 2
 network 10.10.255.1/32 area 0
 network 10.10.10.1/32 area 0
 network 172.20.1.1/32 area 0

================================
Switch A:

interface e1/1
 ip address 172.20.1.2/30
 no shut

interface e1/2
 ip address 172.22.1.5/30
 no shut

interface loopback 0
 ip address 10.10.255.2/32
 no shut

router ospf 2
 network 10.10.255.2/32 area 0
 network 172.20.1.2/30 area 0
 network 172.22.1.5/32 area 0

=================================
Switch C:

interface e1/2
 ip address 172.22.1.6/30
 no shut

interface loopback 0
 ip address 10.10.255.3/32

router ospf 2
 network 10.10.255.3/32 area 0
 network 172.22.1.6/30 area 0

I could be wrong but I think the problem is from switch A, as of today I see SW A's ospf database still showing the old ip address of vlan 10 which from switch B :

Switch-A# sh ip ospf database
        OSPF Router with ID (10.10.255.2) (Process ID 2 VRF default)

                Router Link States (Area 0.0.0.0)
 

Link ID         ADV Router      Age        Seq#       Checksum Link Count
10.10.10.2    10.10.255.2       2        0x8000008c   0x7d9f

My question is how do i update the ospf database of switch A? I was thinking about run 'clear ip ospf process' on switch A but worried about it would drop other routes on switch A. Any suggestions?

The attachment is the map how these switches are connected.

Thanks.

[Peter Paluch]

Hello,

That show ip ospf database output says something different. First of all, the heading of the output - Router Link States - contradicts the entry that is shown. If that was truly a LSA-1, the Router Link State, then the Link ID and ADV Router columns would have an identical number there - but in your output, they differ. Furthermore, a LSA-1 would have a number indicated in the Link Count column, but your output does not show any number in that column. Finally, the output says that the Switch A has its Router ID of 10.10.255.2. Also, the database entry shown in your output is originated by 10.10.255.2 so it means that this is something that is originated by Switch A, not by Switch B.

What I strongly suggest as the first thing to do is to check whether your three switches have unique Router IDs. You can use show ip ospf, among other commands, to check for the Router ID.

Second, would it be possible to actually post the entire output of show ip ospf database on Switch A?

Best regards,
Peter

[tinhnho123]

Hi,

I did take a look again and see that i pasted wrong output of 'sh ip ospf database' of switch A. Below are the output of 3 switches.

Switch-C(config-if)# sh ip ospf database
        OSPF Router with ID (10.10.255.3) (Process ID 2 VRF default)

                Router Link States (Area 0.0.0.0)

Link ID         ADV Router      Age        Seq#       Checksum    Link Count
10.10.255.1     10.10.255.1     574        0x80000006 0xec64   2
10.10.255.2     10.10.255.2     86         0x80000006 0x89f9     3
10.10.255.3     10.10.255.3     85         0x80000003 0x392f     1

                Network Link States (Area 0.0.0.0)

Link ID         ADV Router      Age        Seq#       Checksum
172.20.1.1      10.10.255.1     575        0x80000002 0x95c3
172.22.1.6      10.10.255.3     85         0x80000002 0x53fa

Switch-C(config-if)#
===============================
Switch A:
Switch-A(config-if)# sh ip ospf database
        OSPF Router with ID (10.10.255.2) (Process ID 2 VRF default)

                Router Link States (Area 0.0.0.0)

Link ID         ADV Router      Age        Seq#       Checksum Link Count
10.10.255.1     10.10.255.1     635        0x80000006 0xec64   2
10.10.255.2     10.10.255.2     147        0x80000006 0x89f9   3
10.10.255.3     10.10.255.3     147        0x80000003 0x392f   1

                Network Link States (Area 0.0.0.0)

Link ID         ADV Router      Age        Seq#       Checksum
172.20.1.1      10.10.255.1     636        0x80000002 0x95c3
172.22.1.6      10.10.255.3     148        0x80000002 0x53fa
Switch-A(config-if)#
================================
Switch B:
Switch-B(config-router)# sh ip ospf database
        OSPF Router with ID (10.10.255.1) (Process ID 2 VRF default)

                Router Link States (Area 0.0.0.0)

Link ID         ADV Router      Age        Seq#       Checksum Link Count
10.10.255.1     10.10.255.1     690        0x80000006 0xec64   2
10.10.255.2     10.10.255.2     203        0x80000006 0x89f9   3
10.10.255.3     10.10.255.3     203        0x80000003 0x392f   1

                Network Link States (Area 0.0.0.0)

Link ID         ADV Router      Age        Seq#       Checksum
172.20.1.1      10.10.255.1     690        0x80000002 0x95c3
172.22.1.6      10.10.255.3     204        0x80000002 0x53fa

As of today, I still can't ping 10.10.10.1 (SVI 10 on switch-A) from switch-C.

Thanks.

[Jon Marshall · Accepted solution]

The OSPF database output shows a link count of 2 for 10.10.255.1 ie. switch B.

But it should be a link count of 3 because that is the number of links it has.

Can you check whether the SVI is actually up/up on switch B ie. do you have a trunk link to another switch or an access port in vlan 10 that is up/up ?

Jon

[tinhnho123]

Thanks a lot Jon! the trunk port to another access switch was down. I fixed and it's all good now.

Also I wanted to thank to Peter.