Having both dhcp3 server and dhcp3 relay on the same host
dhcp1 at thehobsons.co.uk
Wed Mar 21 17:34:02 UTC 2007
Laurent CARON wrote:
>I'm considering installing dhcp3 relay on my linux boxes.
>I already have dhcp3 server running.
>Wouldn't those packages conflict ?
Yes, they both listen on the same port - and because they deal with
broadcast packets you cannot get around this by adding a second IP
>Is it a correct behavior to run dhcp3 relay as a fallback if the dhcp3
>server is unavailable (misconfigured, crashed...)?
You can run a relay agent and a server on the same subnet, in the
same way as you can run two servers on the same subnet*. However, you
MUST take steps to avoid conflicts and it is generally inadvisable
unless the two servers are running as a failover pair.
* From the clients point of view, dealing via a relay agent is very,
very similar to dealing with a local dhcp server.
Don't forget that a relay agent does not have to run on a router, it
can run on any machine on the subnet.
As for availability, don't forget that the DHCP server dying will not
make your network crash - it will only prevent clients
obtaining/renewing leases. For Windows clients, they will continue to
use their existing lease even after a shutdown as long as it is still
valid. Not having a dhcp server will have most impact on Macs
(release their lease on shutdown) and on laptops moved from another
network. If your lease times are measured in weeks, then loss of a
dhcp server may go unnoticed for a few days !
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