Just at holiday season begins, it looks very much as if various service providers and backbone connection suppliers have been very busy.

Lots of services have had their public IP addresses updated; I am getting calls from clients whose internal systems don’t genuinely use a domain name to get to a service. It’s not uncommon for all manner of software products (including router firmware) to let you type in www.pcpro.co.uk, and then look it up at that moment and convert it to 212.100.242.151 – which is what they then store for future connection attempts.

When we decide to change that underlying server address – which isn’t a bad thing to do, it’s a supported and allegedly seamless choice for a connectivity person to make – these various bits of software and hardware that use “one-shot lookup” simply fail to re-connect the PCs behind them.

According to a few webmasters, this effect includes some of the mass-market BT Broadband routers – you may well see a little note on some sites telling users to reboot their routers in order to bask in the full feature set of the site, for exactly this reason.

Of course, if you have gone away on holiday as all this has started, and you’re expecting to use remote access, or for your servers to carry on being available when they are behind a device which stores numeric IPs after you’ve typed in a name-style address, then you are out of luck. And you wouldn’t necessarily be able to test for this effect when you chose either your ISP or your router and firewall hardware.

On the bright side, a cold restart seems to sort out the problem, in most cases, so you won’t have to give the house-sitter, dog-walker or next-door neighbour the management interface password to your border device, while standing pumping Swiss francs into a callbox at the top of the Spluegenpass (or wherever).

Pull the power lead, count to 20, bang it back in, wait for the little red light to go green.