Solved: Re: WLC4402: same VLAN, different subnet - can it work?

PetriSignal · ‎02-27-2011

Hi,

I bumped into a interesting issue with WLC4402. Management interface and prod-interface were in a same vlan, but they have different subnets. It seems that "there are two subnets in a same vlan" - 192.168.66.0/24 is defined as primary network in the router and 192.168.72.0/24 as secondary. See the pic attached.

At the moment there is v.4.2.176.0 running and it works. When I tried to upgrade it to v.6.0.199.4 something goes wrong. Controller changed prod-interface port to 0 and I can't change it back to 1 or 2. My best quess is that the WLC is not able to handle this kind of setup...but why is it working at the moment??

Any comments would be most appreciated. Thank you.

-Petri

Nicolas Darchis · ‎02-27-2011

It's actually a wonder/miracle that someone was able to configure this in the first place, to my opinion.

Maybe it was configured with an old WLC release and survived with the upgrade to 4.2

For sure, this is definitely something that the WLC now prevents you to configure. It's not supposed to work, just an example, if you get layer 2 traffic on that vlan (arp for example), where to reply ? you can't know from which subnet it comes from. So it basically means that you are bridging the 2 subnets together and then why not just giving them the same vlan id then ? effect would be the same.

It's anyway going against the linux routing engine, so I'm still wondering how it was working on 4.2

It was probably bridging vlans and doing some unefficient forwarding without you realizing it. So definitely something you should avoid configuring.

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Nicolas Darchis · ‎02-27-2011

It's actually a wonder/miracle that someone was able to configure this in the first place, to my opinion.

Maybe it was configured with an old WLC release and survived with the upgrade to 4.2

For sure, this is definitely something that the WLC now prevents you to configure. It's not supposed to work, just an example, if you get layer 2 traffic on that vlan (arp for example), where to reply ? you can't know from which subnet it comes from. So it basically means that you are bridging the 2 subnets together and then why not just giving them the same vlan id then ? effect would be the same.

It's anyway going against the linux routing engine, so I'm still wondering how it was working on 4.2

It was probably bridging vlans and doing some unefficient forwarding without you realizing it. So definitely something you should avoid configuring.

George Stefanick · ‎02-27-2011

yea Nicky is right ... wont work with newer code. In fact, I was messing around with a anchor controller and tried to put

managment and dynnamic interface in the same subnet and the WLC flagged it as an error.

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
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PetriSignal · ‎03-02-2011

Thanks for the answers. Maybe I leave it like it is and hope the network stays up. Changes in the lan aren't welcome when I consulted the customer.

-Petri