Cat 6509 Assign a port to Two VLANS

[Cedrick]

Hello,

How can you assign a port to two VLANS on a Catalyst 6509? I have a server that I would like to have two IP addresses on and be a member of two VLANS.

Thanks!

 

[BuckWeet]

IOS or CAT OS?

If its IOS, you need to do a trunk port, and if its CAT OS you need to do an AUX vlan.

 

[Cedrick]

It's IOS. Gimme a hint? Thanks.

 

[ADB100]

With either CatOS or IOS you can't do Multi-VLAN ports like you can with a 2900XL/3500XL. If you want a port in multiple VLANs with a Cat 6500 then you must use trunking - either 802.1q or ISL - but your Server NIC must support trunking as well (most Intel NIC's support this anyway).

I really think you should look at what you are trying to achieve here anyway - why not just let the MSFC (Routers) handle the inter-VLAN routing and not bother on the Server? It will only get more complex if you have to maintain a routing table on the Server as well as the Routers?

Don't try and over-complicate things as trouble-shooting just turns into a nightmare

Andy

 

[lui3]

another option is to use two nics and two ports on the switch. place each port in a different vlan on the switch adn make sure the subnets correspond to the configurations on the nics on the server. and voila two vlans/subnets on the same server. just make sure the server is setup for routing or if it is bridging make sure it doesn't loop up.

 

[bierhunter]

Cedrick,

What are you really wanting to do here?

I'm guessing one of the following:

1. Two vlans talking to the same server.
In this case, the server could be in either vlan as long as there is a route to it.

2. Two vlans talking to the same server, but not able to talk to each other.
In this case, I would put the server in a 3rd vlan and apply access lists to control traffic between the vlans.

3. Two vlans talking to the same server, but no layer-3 capability.
You could throw in a 2nd NIC and plug into two ports.

4. Two subnets on one vlan.
Here, I'd just add a second subnet to the vlan. Although, I'd prefer supernetting, there are times when two distinct subnets are required on one vlan (ie...migrations, etc).

If you could give us an idea of what you're really wanting to do, we may be able to assist in a solution.

Thanks.

BierHunter
CNE, MCSE, CCNP

 

[Cedrick]

Well, the reason I'd like to do this is because the server in question is running software that communicates to our big UPS (via SNMP on a card on a Liebert 80KVA NPower). This server, the UPS agent, monitors other servers that have a UPS client on them and they in turn talk to the UPS agent as well.

This software is by no means intelligent. We've added second gig NICs to many of the UPS clients on a private VLAN for backup purposes. The UPS software randomly attaches its service to any NIC in the client (I spoke to the UPS software support people and they verified this and, as luck would have it, the software does not support multiple NICs). Some servers have the UPS service attached to the public NIC we would like to use and others to the private NIC, which we would rather not use, but are being forced to. Once attaced to a specific NIC, the service stays attached to that NIC. Also, we do not want to route the private backup VLAN for security purposes.

I have tried putting a second NIC in the private backup VLAN on the UPS agent and have noticed using a sniffer that some communications to UPS clients are "leaking" through the private NIC even though they should be sent out the public NIC. The local routing tables on the servers look OK. This software is very frustrating. So my thinking was to try to multinet a single NIC hoping to try to get around the UPS software limitations by having all communications to the UPS clients, either on a public VLAN or the private VLAN, pass through one NIC. I’ve also looked into trying to force the UPS service to attach to the NIC we’d like it to be attached to with no luck…So if anyone has any ideas about that please let me know!

Thanks again.