Having problems sending DHCP information over wireless bridge

Jouni Malinen jkmaline at cc.hut.fi
Tue Oct 5 23:45:02 EDT 2004


On Tue, Oct 05, 2004 at 09:58:53AM -0700, Jonathan Shahariw wrote:
> Hi I have a network where we use a linux box with hostap running dhcpd to
> allocate addresses.  Some of the wireless clients for this system are
> Linksys WET11's that are a wireless to ethernet bridge.  The WET11's don't
> have a problem associating to the wireless network.  However, the AP does
> not send the dhcp replys to the hosts on the otherside of the wet11's
> because they are not associated as they don't have wireless cards but talk
> to the network via the WET11.  All other traffic goes through fine if the IP
> address is set statically.  It seems that only the DHCP traffic is blocked
> by hostap.

Host AP is not blocking "DHCP traffic". It will not send unicast packets
to addresses that have not associated because IEEE 802.11 standard does
not really allow such addresses to be used as the source address in the
other direction..

Are you sure your DHCP server is sending the reply back to the expected
layer 2 address? All the requests are coming in with WET11's address as
the source L2 address, but they are likely to have the wired client
address in one or more DHCP packet fields. If the reply is from DHCP
server is going to one of these addresses and not the L2 src address of
the request, it will not get through..

Which DHCP server are you using? Would you happen to have a sniffer log
(e.g., tcpdump/Ethereal with full packet data) from the AP?

-- 
Jouni Malinen                                            PGP id EFC895FA



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