Hi !
The capture you've done is normal under most aspects, but there is something strange in the last 2 rows.
It's normal behaviour for WinXX to set the default gateway the same as the acquired address when using RAS. This is also possible on a LAN card and only means that the PC always resolves addresses/routes by itself instead of relying on an external gateway. There is no way to force the netmask to /24 and it brings also nothing.
You could also pass a DNS end/or WINS address to your clients via the 2509, which you don't do as I see.
The strange thing in the last two rows I meant above is the date reference of the lease.
Did you set the clock of yout 2509 by hand or via SNTP ? It looks as if the date is 01 jan 1980 at noon, and the same data results as expiration time. This coud mean that if a second client dials-in, the address you originally had coud be considered as available and assigned to the newcomer. This is only a doubt but could explain why you can work for some time prior to loose connection. I don't know of any other cache or timed mechanism which expires in about 30 minutes as you said in the initial question. Maybe this is the right direction to investigate instead of caring of addresses and netmasks that remain stable over time.
Have you tried with a "tracert -d [destination]" from the client when the problem occurs ? Where does it halt ?
Have you done any debug on the router side ? And some "show dialer map" or "show ip route" ?
BTW, there are a lot of known issues un this topic in the MS online searchable Knowledge base.
Some documents are also to find on CCO. Just launch a search.
I can't find it anymore, but one of this explained the way MS-RAS assigns addresses/masks and how it works in detail.
A li'l bit long but hope this helps
