Configuring PIX to allow DHCPRelay Agent

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Nov 15th, 2007
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I'm attempting to pass IP's from my pix501 (which is the dhcp server) to clients on the wireless lan controller. The controller acts a dhcp relay agent and I get this in my pix debug:

DHCPD: DHCPDISCOVER received from client 0100.18de.19ab.b9 through relay 192.168


, packet discarded

What can I do to force the pix to allow this through and reply with an IP for the client?



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irisrios Wed, 11/21/2007 - 12:03
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On the controller you would normally associate an interface to a WLAN. While creating an interface that corresponds to the WLAN you have an option to specify DHCP server . Configure PIX as a DHCP server and see if this works.

shensimpson Thu, 02/06/2014 - 07:18
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I am having the same issue, just wondering if anyone has found a solution.  I am trying to configure an Alcatel Wireless controller to use a PIX firewall.  Wireless clients are not able to obtain an ip address via DHCP.  The PIX reports:

DHCPD: DHCPDISCOVER received from client 0100.1302.5e8f.50 through relay

, packet discarded

Notice that the client Mac address is too long  "01" is being added to the beginning.  I have verifified that the Alcatel controller works when connected to a "Linksys" broadband router.

I would greatly appreciate any help you can offer.


Jouni Forss Thu, 02/06/2014 - 14:28
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To my understanding no Cisco firewall model will support acting as a DHCP server for hosts which DHCP messages are relayed by another device in between the client and the firewall. They would only be able to act as a DHCP server to a directly connected network or relay DHCP messages from a directly connected hosts to a server behind another interface of the same firewall.

- Jouni

shensimpson Fri, 02/07/2014 - 07:12
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Yeah that's the conclusion I came to as well.  From the Cisco PIX command reference:

"The PIX Firewall DHCP server daemon does not support clients that are not directly connected to a

firewall interface"

Thanks for your help!


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