dhcrelay over wireless mesh

Alex Bligh alex at alex.org.uk
Wed Jul 11 14:45:00 UTC 2012

--On 11 July 2012 16:06:20 +0200 Luca Tavanti <luca.tavanti at iet.unipi.it> 

> "we completely bypass the Linux IP stack" (btw, does this means also that
> iptables won't work with the ISC dhcp suite?).

Pass, but what it means is it isn't using the UDP stack the kernel provides
to the application (not that it is directly accessing the hardware). It's
doing something similar to what running tcpdump on the interface would do.

> Now, my setup is as follwos:
> ((( 0 ))) ((( 1 ))) ((( 2 ))) ((( 3 )))
> I put the dhcp server on node 0, and both a dhclient and a dhcrelay on
> nodes 1,2,and 3.
> In this way both nodes 1 and 2 gets an IP from the server (directly for
> node 1, through the relay on node 1 for node 2).

Run tcpdump on node 0, and see if you receive the bootp packet, but
earlier you wrote:

> However, OLSR does not seem to route BOOTP packets.

If true, that would be an issue, as bootp/dhcp packets when relayed
are still bootp packets.

Perhaps you meant "OLSR does not seem to forward *broadcasted* BOOTP
packets". Unless OLSR works very differently from every other routing
protocol, OLSR won't forward any packets at all. It will simply populate
the RIB/FIB (the kernel routing table on Linux) and should be agnostic
as to what those packets contain.

Alex Bligh

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