static IP assignment through a bridge ...

Glenn Satchell Glenn.Satchell at
Tue Feb 20 13:35:22 UTC 2007

The dhcp server never sees a packet with the MAC address of the
*bridge* so it will not be able to do assignment based on this. The
bridge forwards packets with their original MAC address. So you will
need to do this another way.

One possibility is to get the bridge to add an option 82 to the packet,
the option agent.circuit-id or option agent.remote-id if the bridge
supports these. See the man page for dhcp-options for more info. You
could use these with a class or sub-class. These are covered in the
dhcpd.conf man page, and a search of th elist archives will also give
useful information.


>From: "Frank Bulk" <frnkblk at>
>To: <dhcp-users at>
>Bridges are layer-2 devices, so if it auto-learns the MAC addresses on each
>connected segment, as most of them do, this should work just fine.
>If I understand your question correctly, if you create a static assignment
>in your DHCP config, your router, which has a fixed MAC address on its WAN
>interface, should get the same IP address every time.
>-----Original Message-----
>From: dhcp-users-bounce at [mailto:dhcp-users-bounce at] On Behalf
>Of Eoin Verling
>Sent: Tuesday, February 20, 2007 6:32 AM
>To: dhcp-users at
>Subject: static IP assignment through a bridge ...
>I'm wondering if the following is possible
>dhcp server  -> ethernet -> Bridge device -> ethernet -> router (dhcp  
>Is it possible to statically assign an IP address, to the router,  
>based on the MAC address of the Bridge? ie, no matter what device is  
>put inside the bridge, an IP will be given to it, same one each time?

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