Hi Brian,

Just wanted to keep you abreast of goings on with the connection problems as 
it's been a while and left you hanging after your last reply.

Based on our discussions it seemed fair to say the problem is network related 
rather than a problem with courier-imap. Based on that and advice from Drew 
Gibson ( also from this list ) regarding network problems I have been looking 
at our physical network and the connecting parts i.e. switches etc.

A major component of the network connectivity is a managed switch situated in 
our sales office through which all network traffic from that office ( where 
the machines having problems are based ) to our server room and IT office. 
This seemed like a good place to start looking. I discovered that this switch 
had an uptime of about 2 years since it's last reboot and that although it is 
a managed switch it had never been configured. I concluded that a full reset 
of the switch could clear any stale ARP table entries which might be causing 
strange behaviour and since the switch was not configured I would not incur 
any other unexpected problems. I've also checked all the patch cables with a 
cable tester and replaced as needed.

I pleased to report that since the switch reboot ( about a week ) I have had 
hardly any reports of e mail problems. Although I am not 100% convinced the 
problem has gone away completely it appears that for now at least it has been 
minimised.

I am in the middle of planning a restructure of our network for a new network 
storage project which should give me an opportunity to sort out the company 
wide connectivity once and for all.

I'd like to thank you and Drew for all your help and advice.

Kind regards,

Adrian

On Friday 06 July 2007 13:04, you wrote:
> I think you should keep it on list, since it's gone this far :-)
>
> > It's interesting that you say this since I have on occasion seen odd
> > behaviour on the network after reboots on some machines. To give you an
> > example if the mail server is shutdown and I try to ssh to it I get a
> > warning that the host keys don't match, when I investigated this I found
> > that I was getting connected to one of the other servers.
>
> Then definitely one of them is coming up on the wrong IP address. Once
> connected to the wrong server, you should immediately type "ifconfig -a" to
> show all the IP address(es) it thinks it owns.
>
> > Both run Ubuntu Linux although the different releases.
> >
> > This also sometimes happens after a mailserver reboot, I've found that
> > the quickest solution to be able to connect again is to reboot my
> > workstation ( I also seen this problem on my laptop when connecting from
> > that ) at which point I connect to the correct machine again. It seems to
> > be off by one on the IP address. I think I need to take a careful look at
> > the other server.
>
> "Reboot the client" is a hack. It will still randomly pick one or the
> other; depending on which responds to ARP quicker you may then get the
> "right" one.
>
> > No backup IMAP although there is the old mail server but that has never
> > been on this IP address. Interestingly I have been told today that people
> > would sometimes get the the same problem connecting to this server ( the
> > old one ) but it was not that frequent ( about the same level as I'm
> > seeing with the 100m/b network card I'm told ). To me that seems to
> > indicate a network related problem rather than software
>
> Two machines on the same IP address is a problem with configuration of
> those machines - unless your network is *really* funky and you have some
> device which is spoofing ARP responses.
>
> B.

-- 
Regards,

Adrian Portway 


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