dns and isp redundancy ? why would i need to restart bind after a isp failover ?

[Tom V]

Hi,

One of our customers has a firewall setup with isp failover (meaning, when
one link to internet fails, we can switch to a standby link from another
provider). Obviously, in this case our public ip adress also changes.

Normally, this should not have any influence on the applications.

However, today we had to switch over to another provider, and we noticed
that our internal dns server wouldn't resolve any external adresses
anymore. we always got a 'no servers could be reached' whenever we tried
to resolve a domain that wasn't local or in the cache.

We solved the problem by simply restarting bind (this is bind 9 on redhat
linux enterprise 3). So it wasn't an access list somewhere that caused the
problem.

Any ideas what could have caused this ? I'm sorry that i don't have more
information for you to work with.


Regards,

Tom.