DHCP Across Wireless Bridge

[Glenn Satchell]

Hi Anthony

That config looks like it should be ok. As you are seeing the discover
packets, then traffic is getting through from the clients and the dhcp
server is replying. However the next thing should be a dhcp request packet
from the client which you're not seeing.

Can you run a packet capture on a client connected to the wireless bridge
and see which parts of the traffic you can see? What you'd be looking for
is whether the client sees the offer from the dhcp server, and if it does
whether it then sends a dhcp request back to the server.

Perhaps also try a packet capture on the dhcp server to see if the request
is coming in, but is somehow not accepted by the dhcp server daemon.

Two minor things with the config: the top end of the range is the
broadcast address (10.7.17.255), perhaps reduce that to 10.7.17.254. The 
host dwight has a fixed ip address that is inside the dynamic range. While
it may never be a problem, it's better to either break the range around
that address (have two ranges: 100-199 and 201-254) or change it to have
an ip outside the dynamic range. Neither of these two problems would stop
dhcp working though.

regards,
-glenn

On Sun, December 29, 2013 6:36 pm, Anthony Hoppe wrote:
> Hello All,
>
> I've been experimenting with isc-dhcp-server on my home network and have
> run into a snag.  I have three devices (Xbox 360, Samsung Blu-Ray Player,
> and a Dish VIP 722 HD-DVR) connected to a switch which connects to a
> wireless bridge.  In my previous setup (using my Cisco 871 router running
> C870-ADVIPSERVICESK9-M ver 12.4(24)T as a DHCP server) these devices were
> able to receive DHCP addresses without any problems.  However, with
> isc-dhcp-server, they are unable to receive addresses.  Reviewing
> /var/log/syslog shows many DHCPDISCOVER/DHCPOFFER pairings as seen below
> (an example of one device):
>
> -----
>
> Dec 28 23:28:13 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:13 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:15 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:15 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:17 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:17 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:31 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:31 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:33 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:33 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:35 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:35 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:49 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:49 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:51 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:51 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
> Dec 28 23:28:53 dns dhcpd: DHCPDISCOVER from 00:08:89:e4:dd:df via eth0
> Dec 28 23:28:53 dns dhcpd: DHCPOFFER on 10.7.17.101 to 00:08:89:e4:dd:df
> via eth0
>
> -----
>
> Connecting a known working computer to the switch behind the wireless
> bridge also results the same...it is not able to obtain a DHCP address.
>  DHCP works anywhere else on the network without a hitch.
>
> Some Googling around leads me to believe the culprit is likely the
> wireless
> bridge.  I am using an EnGenius WAP (I can't find and/or recall the model
> at the moment) in client bridge mode.  However, like I said earlier, DHCP
> worked fine in my previous setup.  Is there a way to configure
> isc-dhcp-server so that it will work, too?
>
> Here is my dhcpd.conf:
>
> -----
>
> authoritative;
> option domain-name "hhsn.net";
> option domain-name-servers 10.7.17.24;
>
> ddns-updates on;
> ddns-update-style interim;
> ignore client-updates;
> update-static-leases on;
>
> default-lease-time 86400;
> max-lease-time 86400;
> log-facility local7;
>
>
> include "/etc/dhcp/ddns.key";
>
> zone hhsn.net. {
>   primary 10.7.17.24;
>   key DDNS_UPDATE;
> }
>
> zone 17.7.10.in-addr.arpa. {
>   primary 10.7.17.24;
>   key DDNS_UPDATE;
> }
>
>
> subnet 10.7.17.0 netmask 255.255.255.0 {
>         range 10.7.17.100 10.7.17.255;
>         option routers 10.7.17.1;
>         option broadcast-address 10.7.17.255;
>         option subnet-mask 255.255.255.0;
> }
>
> host dwight {
>  hardware ethernet 00:23:DF:7F:28:04;
>  fixed-address 10.7.17.200;
> }
>
> host nettalk {
>  hardware ethernet 00:25:F6:00:3A:B4;
>  fixed-address 10.7.17.20;
> }
>
> -----
>
> Any assistance would be greatly appreciated.  I am using isc-dhcp-server
> version 4.2.2 on Debian 7.
>
> Thanks!
>
> ~ Anthony