WLC 2106 does not send DHCP request

Unanswered Question
Sep 7th, 2009
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I've several WLC2106 running 4.1(185) and all is working fine.

Now we started to migrate some of them to 4.2(207) but client didn't received anymore DHCP reply.

DHCP server is a Microsoft server with the address configuren under the dynamic interfaces parameter.

With the same config and 4402 all is working fine.

With the same config and 4.1.x with WLC2016 all is working fine.

It seems something changed from 4.2.

Any idea ? Here the log of DEBUG DHCP PACKET

00:22:fb:89:d1:dc DHCP received op BOOTREQUEST (1) (len 312, port 1, encap 0xec03)

00:22:fb:89:d1:dc DHCP processing DHCP DISCOVER (1)

00:22:fb:89:d1:dc DHCP op: BOOTREQUEST, htype: Ethernet, hlen: 6, hops: 0

00:22:fb:89:d1:dc DHCP xid: 0x5cbacd54 (1555746132), secs: 3, flags: 0

00:22:fb:89:d1:dc DHCP chaddr: 00:22:fb:89:d1:dc

00:22:fb:89:d1:dc DHCP ciaddr:, yiaddr:

00:22:fb:89:d1:dc DHCP siaddr:, giaddr:

00:22:fb:89:d1:dc DHCP requested ip:

00:22:fb:89:d1:dc DHCP successfully bridged packet to DS

00:10:18:3d:9c:2b DHCP received op BOOTREQUEST (1) (len 268, port 1, encap 0xec00)

00:10:18:3d:9c:2b DHCP dropping packet (no mscb) found - (giaddr, pktInfo->

Many thanks


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weterry Mon, 09/07/2009 - 09:00
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"00:22:fb:89:d1:dc DHCP successfully bridged packet to DS" means that you have dhcp proxy disabled on this controller.

If DHCP Proxy is disabled, then the controller is no longer involved in the DHCP process and this is requiring you to have IP HELPERS in place on your router to get these dhcp requests to the correct server.

If you want DHCP Proxy enabled (so that you can use the DHCP configuration under the interface or the WLAN on the controller) you can do "config dhcp proxy enable"

LUIGI PIETRONAVE Mon, 09/07/2009 - 12:18
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Thank You very much for the answer,

tomorrow i'll try but something changed from 4.1 to 4.2 ?

With the previour release all was working fine.

Many thanks


weterry Mon, 09/07/2009 - 13:01
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In 4.1, disabling DHCP proxy did just that, it disabled the "proxy". If you ever look at your dhcp lease of a wireless client, it comes from a dhcp server of (virtual IP of the controller). With proxy disabled, the address will no longer be masked.

In 4.2 and beyond, disabling dhcp proxy actually disables the DHCP Relay that is the process of the controller sending the dhcp requests to a specified server.

So if in 4.1, you had "dhcp proxy" disabled, in 4.2 and beyond, you are actually disabling the relay as well.

If this is indeed the case, enable dhcp proxy, or add an IP Helper adress to your router for this vlan, just like you would normally do for Wired clients.


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