Bind 9 slave doesn't resolve hosts if the master is down.

Hello all,

I have bind 9 configuration I thought I understood, however I now know I
don't.

I have 1 master server and 1 slave server.

I shutdown the master server and login to the slave server dig still manages
to lookup domains using the slave server, if I login to the master server
and use dig to lookup domains against the slave server this still works, as
expected.

However if I go to a webbrowser and lookup a web domain that is served on
both the master and the slave with the master still turned off the request
times out.

I can only put this down to a few things

1.) The time out searching for the master server is longer than the
webbrowsers timeout. so how do I check / fix this.
2.) The slave server is not serving / acting as an SOA for this domain
(which I think it is as I can do lookups on it when the master is down)
3.) There is some sort of problem with external clients resolving domains
against the slave (I think not as most of the look ups seemed to be served
by the slave even when the master is up)

4.) something else....open to suggestions


thanks,

Matt.