Can't connect to a set of IP's without a reboot?

[neil.potter]

Ever since I moved in to my new house 6 months ago and setup with an O2 broadband box I'm having trouble connecting to my work servers, as below.

IP at home (o2) is 94.192.8.100, off the back of an o2 TG585v7 (7.4.20.5)
At work we have a few servers (email, web, vpn) behind ip's 78.86.234.220 to 78.86.234.223. This range is on a Cerberus (Part of Be who also run o2 i think) adsl2 link.

My issue is this. Often when I get home from work, and try to connect up to email / vpn / or our intranet site, my o2 connection says it can't connect to the servers. Whether via web/email/vpn/custom ports. All sorts really. It looks as though our work connection has gone down or doesn't exist. However, if I reboot my o2 box, as soon as it comes live, I can connect to work again.

Now I know it shouldn't be an issue at work as I can always connect from my iPhone via 3G, and all other non O2 users can connect all the time. I know 3 other staff at work who are on o2 and also have the same problem, which a reboot always cures.

To complicate matters, we have a tiscali link at work linked to the same firewall (a sonicwall 2040) which always works from home if I manually change ip's etc in VPN links / email settings.

So it's almost as though the issue is only between "any" o2 ADSL2 link and our office ADSL2 link.

I've spoken to both parties and they just point the issue at the other which doesn't help.

I've tried a 3rd party router, but as I say, I know other people with the same setup who also cannot connect.

Bar changing my work internet connection, which obviously isn't an option, does anyone have any ideas what is going on, and how I can solve it?

Thanks

Neil

[Tony1044]

Out of interest, what model was the third party router?

The only two things that spring to mind with it working for a short period of time after reboot is that the router is applying a firewall policy that takes a few moments to take, or if your IP is changed after a reboot, your company firewall doesn't like something about the machine or IP range you are on.

[neil.potter]

Thanks Tony.

The 3rd party box I put in place was a Zyxel 660.

I'm fairly happy that it;s not my firewall at work as the rules are the same on the two links I have there, and I've even tested by disabling the firewall in the office and at home. Ands when I say short period, it could be hours. It only fails when not used for a while i.e. if I turn my laptop off overnight, I can;t connect to work in the morning. Nothing else has been rebooted. My O2 box retains the same IP every time. It's really puzzling.
Nothing shows in the logs on the firewall at work so I assume the firewall that my connection isn't getting as far as work?