On Fri, 2007-02-09 at 13:12 +1030, Kim Hawtin wrote:
[...]
> Jon Smirl wrote:
> > Is there any way for DHCP to work on an OLSR mesh? It seems like it
> > could propagate out from the DHCP server as each hop came up. A node
> > that wasn't part of the mesh yet would just send out broadcast
> > requests until it got assigned an address.
> 
> in a cisco environment you use IP Helper addresses to deal with it.
> that happens at layer 2, right?

Partly.
The DHCP clients broadcasts on layer 2 (because he can't initially do
anything else) and the relayer receives it and unicasts it to the DHCP
servers (as told in the DHCP relayers configuration) on the layer 3 (and
back the other way round).

> how about something like dhcp-relay on linux?

Yes, that would be the simple solution.
Practically I doubt that it actually makes that much sense in a really
meshed network.
Why?
- You need to run a DHCP relayer on each node. You have to configure it
there
   also. AFAIK there is no infrastructure/means.
   Docs and Patches welcome.
- If the the DHCP server is not reachable because some deciding link is
down for
   an hour, you have to wait.
   Of course you can configure large lease times and the client could
use an too
   old lease but than your violating the protocol.

Of course one can run redundant DHCP servers in different parts of the
mesh but I don't know if there is a free one out there (ISC dhcpd can
run as failover but you rally shouldn't risk to loose the connection in
between. As with all clusters the question is: What happens after a
split brain situation?).

Of course you can run several independent DHCP servers handing out IP
addresses from different IP networks in different parts of the mesh. But
that would defeat the idea of simplicity and central administration
which is IMHO the primary (if not only) reason to run a DHCP server.
And you risk that one DHCP servers runs out of IP addresses while
another has more than enough.

	Bernd
-- 
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