Problem with Nexus 5596 and Cat 3750

[Vinny]

Hi guys,

I have a problem right now.

We are migrating a servers rooms from Catalyst switches to a Nexus 5596 network.

During the migration, I need to connect my old network to my new one.

In this case, I connected a stack a three 3750 to both Nexus. I created a VPC on the Nexus.

Problem is...when both connections are up, I have a lot of lost packet (about 1 of 4 pings are lost). If I unplug one of the connections of the etherchannel, everything works fine. I changed all SPF and fiber cables so I don't think it's a hardware problem.

Take a look of this on the picture. I'm using 1gb SFP because my 3750 don't support 10gb connections

What am I missing ?

Please note that the IOS on the 3750 isn't up to date and I have the latest on Nexus.

Thank you

[dominic.caron]

Hi,

What's the source or the ping?

Can you do a on both nexus switch?

[Vinny]

Sorry forget this detail.

Source is a server on the new network (Nexus) and destination is a server on the old one (3750). In fact the problem occurs on several servers so it's not a problem  related to this particular one.

Nexus-1# sh vpc 2

vPC status

----------------------------------------------------------------------------

id     Port        Status Consistency Reason                     Active vlans

------ ----------- ------ ----------- -------------------------- -----------

2      Po2         up     success     success                   LIST_OF_VLAN

Nexus-2# sh vpc 2

vPC status

----------------------------------------------------------------------------

id     Port        Status Consistency Reason                     Active vlans

------ ----------- ------ ----------- -------------------------- -----------

2      Po2         down*  success     success                    -

Note that Active vlans on the second nexus aren't there because right now the second cable is disconnected.

[dominic.caron]

Did you check the SFP and fiber of the peer-link? If you are the lastest version, bring uldl up.

[Vinny]

Yes I checked them but I pretty sure the problem is between nexus and 3750 because if I move both servers I was pinging on the nexus then I have no problem.

uldl is already up

[dominic.caron]

And if you unplug the other link of the channel

[Vinny]

unfortunately, that's the kind of test I can't make during production time.

There are a lot of tests I want to do during the next maintenance schedule and I'll do this one next time for sure.

[dominic.caron]

I’ve did some test when I first installed this platform but it was with a switch running 12.2(50). I have only a single 5000 in my lab and a pair of 7000.

[Vinny]

I did some tests too a few weeks ago in lab with both nexus running 5.0 (instead of 5.1) with a Catalyst 3560-X (latest IOS) with 10gb interface.

I pretty sure it was working fine...

I have another nexus 5548 in lab, I'll make some tests again.