One of my clients has installed an IP telephone system. Addresses are
assigned to the phones by the Novell DHCP server on a 10 day lease. All is
well until the DHCP server is rebooted. This causes the telephone switch
and all the phones to reset, disconnecting any calls that are in progress at
the time.

I moved the DHCP server to a different Netware box which is rebooted much
more infrequently. I expected the phones to all reset when I did this but
they didn't, suggesting that all they need is an available DHCP server when
they decide to renew.

Has anyone tried running multiple DHCP servers on the same subnet,
allocating from the same address pool? The way I understand it, a client
broadcasts a DHCPREQUEST and may subsequently receive multiple offers from
DHCP servers. After accepting one offer, the client ignores further offers
from other servers, then broadcasts to all DHCP servers that it has accepted
an offer from the identified DHCP server. The IP address is then sent to
the client by the 'winning' DHCP server.

Is this how Novell DHCP server works? If I can have DHCP running on 2
servers, the likelyhood that both will be unavailable when the phones need
to renew (or whatever they are doing) is minimal.