Dual homed trunks from C9300 to C9606R one 10G and one 1G

[wickedevo]

I have a question pertaining to trunks with C9300 and C9600. The C9600s are my core nodes and C9300 is an end building node. I was upgrading the 1G trunks to 10G trunks that I have dual homed from the C9300 to two separate C9600s. I did one at a time and after swapping in the 10G SFPs on the first trunk link it came right up and was passing L2 and L3 traffic no problem but then I noticed on the 1G trunk that is going to my second C9600 that my OSPF Point-to-Point went down. So I SSH'd into both switches and started looking around. I did a "sh int trunk" and no VLANs were being fwd out of either side and like I said the OSPF link was down. When I did a "sho int status" both sides showed as connected and looking at the switches both still had green lights. It seemed as soon as that 10G trunk came up the 1G trunk just stopped passing traffic. With that in mind I ran out and swapped out the 1G SFPs with 10G SFPs so now both are 10G trunks and when I did that all traffic started passing again and OSPF link came right up. It is probably my ignorance and not understanding the network module that is in the C9300 (C9300-NM-8X) and how the 10G and 1G ports work on it.

So, my question is once I change one trunk to 10G do all others after that have to be 10G? Or is it something to the effect that once I bring up a 10G port on that network module the first 4 ports are used for 10G and the last 4 are for 1G?

I have tried googling and finding an answer but to no avail. Any wisdom from the gurus out there would be greatly appreciated. The more I learn the better!

[wickedevo]

Yes OSPF neighbor dropped. Our STP mode is MST so (theoretically) based on the instances we have setup some VLANs should go over one link and some over the other right? Unless I need to brush up on STP a bit more again I understood it as whether one uplink has more BW or not those VLANs should stay split (per our MST config) on those uplinks UNLESS an uplink goes down/down right? I think I am going to go into work tomorrow and set up a little sandbox NET with some spare equipment and see if the same thing happens on a basic little NET. Again thanks for everyone’s input!

[MHM Cisco World]

the VLAN use for OSPF in both C9600 only add it to C9300 and the issue will solved 

[Joseph W. Doherty]

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@wickedevo wrote:

Yes OSPF neighbor dropped. Our STP mode is MST so (theoretically) based on the instances we have setup some VLANs should go over one link and some over the other right? Unless I need to brush up on STP a bit more again I understood it as whether one uplink has more BW or not those VLANs should stay split (per our MST config) on those uplinks UNLESS an uplink goes down/down right? I think I am going to go into work tomorrow and set up a little sandbox NET with some spare equipment and see if the same thing happens on a basic little NET. Again thanks for everyone’s input!

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Correct, you can place multiple VLANs into MST, and if using more than one MST instance, you can have some VLANs use one path while others use an alternative path.

As to fail-over, you would need to have the same MST region allowed to use multiple paths (do you?), you then cost to determine which is to be preferred.  If you break the current preferred path, MST should re-converge to the alternative path, which could take a few seconds.  If you break the alternative path, I believe there should not be any service interruption.

As to OSPF dropping, I'm thinking if MST blocked the lessor bandwidth link, it would also block OSPF hellos. Much depends on how you've configured L2 and L3 interaction.

[MHM Cisco World]

I know what issue here' I run lab to show you issue here 

[paul driver]

Hello
If the two links were independent of each other It somewhat negates a physical issue.
Did you try removing the new 10GB and see if the 1GB ospf peering re-established?
Can you remember what ospf state the 1GB peering failed back to?
Do you have ospf reference BW parity on all L3 ospf processes?