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smp_86112's avatar
smp_86112
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Jan 08, 2009

Routing multiple VLANs to single LTM interface

Let me apologize up front if I mangle the terminology I'm about to use. This type of discussion does not fall within my area of expertise.

 

 

Up until now, we have been routing one VLAN to the floating IP address of the external VLAN on our Active/Standby LTM pair. We now have a requirement to route multiple VLANs to that same LTM interface. So, for example, today we might be routing VLAN 100 to 192.168.0.254, which would be the floating IP address of the external VLAN on our LTMs. In the future, we want to route both VLAN 100 and VLAN 200 to 192.168.0.254.

 

 

What I'm hoping you can clarify is what, if anything, I need to do on the LTM to support this.

 

 

Thanks.

 

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design
  • dennypayne's avatar
    dennypayne
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    Jan 08, 2009
    I'm not sure exactly which scenario you're trying to support here, so I'll try to explain the procedures for both:

     

     

    1. LTM is directly attached to VLAN 100 now and you want LTM to be directly attached to both VLAN 100 and VLAN 200

     

     

    When you define the VLAN you set up the VLAN tag, so you'd have one with tag 100 and another with VLAN 200. Then you assign the same interface under both VLANs as a tagged interface (instead of untagged). The switch then needs to be configured as an 802.1q "trunk" (confusing to some because on an LTM a "trunk" is a 802.3ad aggregate interface).

     

     

    However you will not be able to have the same self IP of 192.168.0.254 on both VLANs. The self IP's on each VLAN will need to be on separate networks.

     

     

    2. LTM is forwarding traffic for VLAN 100 currently and you want it to forward both VLAN 100 and VLAN 200 traffic. (I don't think this is what you are asking but I'm a little confused when you say you are "routing" the VLAN to LTM)

     

     

    Depending on how your forwarding virtual server is currently configured you may not need to do anything. If it's currently a wildcard virtual then just enabling it on the new VLAN should be sufficient.

     

     

    Denny

     

     

  • smp_86112's avatar
    smp_86112
    Icon for Cirrostratus rankCirrostratus
    Jan 09, 2009
    Thank you for the info. It is difficult for me to explain exactly what I mean by "routing the VLAN to the LTM", as our company's routing infrastructure is managed by a different team. My understanding is there is a route on our router which sends traffic on VLAN 100 to our external floating IP address. I realize that is mixing L2 and L3 terms, but I just don't know how to say it the right way, I guess.

     

     

    In any case, you were smart enough to get my point and correctly lay it out in scenario 1. And you have clearly outlined the steps I was looking to understand. Thanks also for the tidbits both about the term "trunk" (which has always confused me), and the note about the networks. I hadn't considered the self-IP item, but that makes sense.

     

     

    Thanks again.