[CLUE-Tech] networking questions

[Dave Anselmi]

Mike Staver wrote:

> I have 3 webservers here at work, 2 running Red Hat 7.1, and another
> running Red Hat 7.2.  They are all in a cluster running cold fusion
> cluster cats.  When one machine goes down, one of the other two assume
> it's role and start listening on port 80 and 443 for the down machine's
> ip address.  My question is this: in Red Hat 7.2, which is the 3rd
> webserver which I just rebuilt, how can I "force" the network to retake
> the ip address x.x.x.23?  One of the other 2 webservers automatically
> takes that ip over when the 3rd box is down, but when I reboot the 3rd
> box, it always used to reassume it's ip when it came back online.  Now,
> it says it can't log onto the network because another machine is using
> it's IP address.  How can I force it to take that IP regardless?

Hi Mike,

Perhaps you've solved this already, but if not I'll take a crack.
Unfortunately I don't run RH, so I can't be too specific.

Typically, IP addresses are assigned with the ifconfig command.  I don't
think it checks to see whether the IP is in use.  I assume that you aren't
using DHCP (in that case your machine would try to get its old IP back, be
denied, and be given a different one instead).

The place ifconfig (or whatever else RH uses for this) is run in in the
boot scripts, which are typically in /etc/init.d.  There should be one
there that does networking, and by looking at it you should find whatever
is doing the IP free check.  If you can't find it, you can look at the
error message you get and use grep (perhaps with find) to find the right
file.

Once you understand how the check is done, you can disable it by rewriting
the script.  If you have further trouble, I'd be happy to help.  Of course
the other question is how does the backup machine release the IP when the
original machine comes back up.  I assume cluster cats handles that for
you.

Dave