topic Re: OSPF learnt route difference with VOSS. in ExtremeSwitching (VSP/Fabric Engine)

OSPF learnt route difference with VOSS.

Anonymous — Thu, 27 May 2021 15:44:26 GMT

Hoping someone more clever then myself can help me workout why a route on the Palo Alto shown below (10.119.71.0) is add a route via the EXOS devices on the EOS switches as you would expect, but I am not seeing anything via the VSP.

I think its to do with the same routes via the VSP being seen as type 3 LSA’s?

In essence I am migrating the the L3 links on the firewalls from EXOS to the VSP’s. The whole Data Centre is run North of the firewall. So I want to be careful about moving the L3 links across so not to cause any disruption.

I don’t think there is anything necessarily wrong, as the VSP learned routes will I believe kick in when fully migrated across, but what to fully understand what I am seeing to be sure it is safe.

Many thanks in advance.

Martin

Re: OSPF learnt route difference with VOSS.

Miguel-Angel_RO — Thu, 27 May 2021 15:50:55 GMT

Martin,

Probably related with ecmp.

Check this:

show ip route alternative

show ip ecmp max-path

Mig

Re: OSPF learnt route difference with VOSS.

Anonymous — Thu, 27 May 2021 16:01:17 GMT

Hi Mig,

Thanks for getting back.

Here is the output taken from VSP-CR1

show ip route alternative | 10.119.71

***********************************************************************************
                Command Execution Time: Thu May 27 08:52:24 2021 GMT
************************************************************************************
=====================================================================================================
                                       IP Route - GlobalRouter
=====================================================================================================
                                                     NH                      INTER
DST             MASK            NEXT                 VRF/ISID         COST   FACE     PROT AGE TYPE PRF
-----------------------------------------------------------------------------------------------------
10.119.71.0    255.255.255.0   172.20.251.65        GlobalRouter     20     3501     OSPF 0   IB   25

show ip ecmp max-path
************************************************************************************
                Command Execution Time: Thu May 27 08:52:37 2021 GMT
************************************************************************************
====================================================================================================
         ecmp-max-path Info - VRF "GlobalRouter" (Global Routing Table)
====================================================================================================
               ecmp-max-path : 8

Which the output looks identical to just looking at the active routing table.

The route is in the VOSS switch, just seems the on the EOS switch it sees the same route learnt via the EXOS switches differently and VOSS - I think, and not sure why, or how to correct (if that is necessary).

Is it that the EOS switch sees the route via EXOS as interarea and VOSS as external? So EOS is just adding the more least expensive route?

Re: OSPF learnt route difference with VOSS.

Miguel-Angel_RO — Thu, 27 May 2021 17:49:56 GMT

Martin,

What are the neighbours on the VSP?

“show ip ospf neig”

Re: OSPF learnt route difference with VOSS.

Anonymous — Thu, 27 May 2021 18:11:51 GMT

Here you go….

Basically what you are seeing is the adjacency on VSP-Core1 & 2 back to the Palo Alto.

VSP-Core1 has an adjacency back to the EOS switch (172.20.250.217 - 2.2.2.2)

Noticed an error in my diagram. There is actually x4 VSP8400’s in this topology, but only added two to the diagram with one of the links to the EOS switches being incorrectly placed, but effectively it will be the same thing.

The other adjacencies are basically a /29 subnet (VLAN 3401) to all the x4 VSP’s mentioned..

One thing to note is that all the subnets north of the Palo are in area 0.0.0.255, but all the connections to all the switches are in area 0.0.0.0

VSP-Core1:1#% show ip ospf neighbor
************************************************************************************
                Command Execution Time: Thu May 27 10:55:03 2021 GMT
************************************************************************************
====================================================================================================
                         OSPF Neighbors - GlobalRouter
====================================================================================================
INTERFACE       NBRROUTERID     NBRIPADDR       PRIO    STATE    RTXQLEN PERM TTL
----------------------------------------------------------------------------------------------------
172.20.250.217  2.2.2.2         172.20.250.218  1    Full     0       Dyn   35
172.20.251.66   172.20.255.111  172.20.251.65   1    Full     0       Dyn   35
172.20.250.129  172.20.248.212  172.20.250.130  1    TwoWay   0       Dyn   31
172.20.250.129  172.20.248.221  172.20.250.131  1    Full     0       Dyn   35
172.20.250.129  172.20.248.222  172.20.250.132  1    Full     0       Dyn   33



VSP-Core2:1#% show ip ospf neighbor
************************************************************************************
                Command Execution Time: Thu May 27 10:55:36 2021 GMT
************************************************************************************
====================================================================================================
                         OSPF Neighbors - GlobalRouter
====================================================================================================
INTERFACE       NBRROUTERID     NBRIPADDR       PRIO    STATE    RTXQLEN PERM TTL
----------------------------------------------------------------------------------------------------
172.20.251.70   172.20.255.111  172.20.251.69   1    Full     0       Dyn   33
172.20.250.130  172.20.248.222  172.20.250.132  1    Full     0       Dyn   40
172.20.250.130  172.20.248.221  172.20.250.131  1    Full     0       Dyn   32
172.20.250.130  172.20.248.211  172.20.250.129  1    TwoWay   0       Dyn   31

Thanks

Re: OSPF learnt route difference with VOSS.

Miguel-Angel_RO — Fri, 28 May 2021 15:51:06 GMT

Martin,

It seems that the EOS is not sending the ip routes to the VOSS.

Can you check with “show ip route protocol ospf”?

Mig

Re: OSPF learnt route difference with VOSS.

Anonymous — Tue, 01 Jun 2021 15:22:00 GMT

On close examination the Palo Alto is using a cost of 10, EXOS is using 14 and VOSS is using 20. So have come to an conclusion the EOS switch is installing the route via EXOS with a preference of 24 rather then 30 via VOSS.

What I expected to see in the EOS routing table (subject to not having a command like show alternative), was the additional route shown via VOSS under the EXOS route, but showing the higher cost - think that’s how its done in EOS. This is what has effectively thrown me off as I have no way of validating it (that I know)

Anyway, the plan is to add some config on the EXOS links to increase the cost to see if the route via the VOSS switch is installed. The premise is that generally everything seems to be OK, adjacencies are all up, routes are being shared, so in theory it should work.

Once I’ve done it and got the results I will post back.

Re: OSPF learnt route difference with VOSS.

Anonymous — Thu, 01 Jul 2021 01:38:24 GMT

Just updating this post based on the results.

After removing the path via EXOS, the routes on EOS showed that via VOSS, so in the end was just related to cost.

The switch over from EXOS to VOSS worked seamlessly as the routes via VOSS kicked in on the EOS switch.