Takes time to look up web pages when the modem/router dials to ISP

I am using
- SIEMENS SL2_141 modem for my DSL connection. (also use Linksys WRT54G)
- Macintosh OSX 10.5 on Macbook Pro


Till yesterday I used to manually dial to my ISP i.e I had a bridged connection. Recently I made the modem to dial it by itself, so that it connects by itself. But now most of the sites takes lot of time to start opening stating "Looking up www.domain..." and it takes a while before it actually opens and some take more than one request i.e in the first try the browser will give a not found and on the retry it works fine.

I am having this problem when I make the external modem/router to dial it. It doesnt have any such delay issue when I manually dial it from the mac through the same router to the same ISP.

Any fix for this ?

Check your settings in the modem for time out or keep-alive. Most likely it's disconnecting after X amount of minutes of inactivity. You can set it to always be connected. That's why your first request fails, the modem needs time to authenticate and once it connects it works fine.