Bootp through WLC 4400 - out of ideas

Unanswered Question
Nov 20th, 2007

We use several (80) wireless bootp devices in our network. They of course have been running great on autonomous APs but refuse to work on our WLC wlans. I did a packet capture on the vlan only to find that the wlc 4404 is retagging the bootp packet source as it's own IP instead of This of course causes the bootp server to send out a bootp reply specifically to that IP instead of a broadcast (where I hope the WLC would behave normally since broadcast forwarding has been enabled).

I'm running version and the results are identical on our 4404 and 4402. I'm out of ideas guys any advice?

proper.pdf shows the process on an autonomous AP at packet 1 and 5. Other packets show the same process through a WLC.

.254 is the bootp server, .240 is WLC

I have this problem too.
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Scott Fella Wed, 11/21/2007 - 19:08

The WLC acts as a dhcp relay so it will use it's IP and will not forward any broadcast.

Richard Atkin Wed, 11/21/2007 - 23:54

On the newer code (either, or 4.2) you can modify how the WLC treats broadcast traffic (ie, forward or drop).

Try enabling broadcast forwarding (from the 'Controller' tab on the WLC GUI) and see if that helps.

mlrtime99 Thu, 11/22/2007 - 06:54

Broadcast forwarding is already enabled, I believe if the wlc wasn't sourcing with it's own IP and gunking up the whole process it would work fine. Look at the packet capture again.

Richard Atkin Thu, 11/22/2007 - 09:46

Okay, well if your DHCP Server doesn't like proxied requests, you've got three options;

1 - Use a DHCP server that will accept proxied requests like a Cisco Switch, the WLC it's self, a Microsoft Server, etc...

2 - Scrap lightweight and go back to IOS

3 - Employ H-REAP, which will then bridge traffic straight on to a VLAN from the AP. This means it won't go via the WLC, and the requests will therefore go un-altered. H-REAP requires 1030, 1130, 1240 or 1250 APs, and the switchport to be altered to a Trunk port.



mlrtime99 Wed, 11/28/2007 - 12:50

DHCP works great, we have several wlans using different servers (cisco 6509, Server 03) and those all obtain IPs effectively

I've done captures on the wired and wifi side and the reply stops when it hits the wireless lan controller.

H-REAP is not as option as one of our partners has supplied about 40 1231's


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