On Thu, 6 Feb 2014 18:02:05 -0000, Andrew Mawson wrote:

Both have fixed IP addresses and work fine, EXCEPT - if not used for a
few hours or sometimes days they are liable to vanish from the network,
not to return unless switched off and then back on again.

I get the same with an HP colour laserjet CP1515n, but it's only the
printing that stops. You can still ping it and explore it's web based
setup pages. The easy way to make it print again is a power cycle. It
doesn't happen very often, maybe once a month. This is on DHCP but
the server is set up so that everything that it has seen before gets
the IP address it had before.

--
Cheers
Dave.