Cisco VLAN Routing to an HP Switch

Posted on 2014-09-04
Last Modified: 2014-09-06
We have an existing C3750X-24 stack and have installed a 10GB module to connect to a new HP switch supplied by a vendor.
The hp switch is on a 192.168.40.xx vlan, and they will be responsible for it's configuration.

We are responsible for configuring the cisco switch (currently just the management default vlan1) 192.168.41.xx

IP routing is enabled, and I can create a vlan for the hp's subnet.... just not sure if I only need to add the 10GB module to the HP VLAN, or all the ports?

If I only add the 10GB interface, will all the other ports see it as a gateway and route through the 10GB module automatically?
Question by:PeppeLaPew
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Expert Comment

ID: 40304675
Generally speaking, vlans only need to be configured where they need to be accessed directly. On the 3750, you will likely need to enable ip routing as you mentioned you have already done, configure the new vlan (both l2 and l3), then configure the 10G port to have that vlan. Although you could configure it as an access port, I would recommend that all switch-to-switch connections be configured as a trunk even if you are only allowing a single vlan to communicate. The HP switch, and any other devices that use the new vlan should be addressed in the new subnet and use the IP on the 3750 (in the new vlan) as a default gateway.

Author Comment

ID: 40305806
OK... So I have created the new VLAN. Assigned it an IP address, added the 10GB module port to the VLAN, Enabled trunking, and dot1q.

I haven't connected the 2 switches yet... is there anything else to do?

I'll attach the cisco config

Author Comment

ID: 40305819
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Accepted Solution

rauenpc earned 500 total points
ID: 40306066
For starters... a hostname of Twinky - awesome.

I don't see the "vlan 2" command in there (but that doesn't mean you didn't enter the command). Make sure that vlan 2 is actually defined from a layer 2 aspect. I've been caught numerous times where I made the "interface vlan x" to create the L3 vlan, but not the required "vlan x" to make the l2 vlan.

The only potential thing left to do is configure the HP switch. You will have to set the 10G port to tag vlan 2, and untag vlan 1 (if you want vlan 1 to be available on the HP). From there, you will probably need to configure vlan 2 on the rest of the ports - usually this would be untagged for the average end device.

One thing to bear in mind... HP doesn't run spanning-tree by default (or at least not in my experience). They also don't necessarily play nice with pvst which is a Cisco technology. If you want to match everything up, you would have to use either STP or MST. That being said, if you have a single connection to the HP switch and will never have a redundant connection, spanning tree doesn't really matter.

Author Comment

ID: 40306331
Dang... connected the 2 switches, and lost access to the Cisco switch... wouldn't respond to anything at the ip address.

Disconnected, and it came back to life.

The HP switch appeared unaffected, but they were not passing traffic.
LVL 20

Expert Comment

ID: 40306673
Please be more specific... you lost access to the Cisco switch as in the whole network went down, or when connected to the HP switch you couldn't access the Cisco switch? Are you able to post the HP configuration?

Also, looking back at the config, you can add the following to the 10G interface:
switchport mode trunk
switchport nonegotiate

Author Comment

ID: 40307447
I was remote to the switch, so all I could tell was the switch stopped responding on it's IP interface. Regardless got it working... not the way I originally wanted, but working. Had to untag packets from the HP switch, and put the port into access mode. (may have changed it to trunk mode after I uploaded the config... I don't really remember)
So it's working, but I think there will be issues if I ever need another VLAN.

Thanks for your help

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