Linux gateway problem.(Please help urgent)

[siddapur]

Dear All,
I have a strange kind of problem in my Linux server. Its IP address is 192.168.100.5 and subnet mask:255.255.255.0 and default gateway is 192.168.100.1 (192.168.100.1 is router IP of DSL router.).I have configured sendmail in Linux for our internal mailing purpose.It is able to send mail to our internal users and also to yahoo and other external mail ids. ( The sendmail is working very fine)
But the problem is, when ever the DSL connection goes down the Linux server becomes very slow. If I try to telnet to that server at that time it takes very long time to connect.Also internal mail also becomes very very slow.Over all the server becomes very slow. If I remove default gateway entry then server is normal even if the DSL connection goes down . But I will not be able send mail to yahoo and other external server although internal mail works still.I think all trafic is being diverted using this DSL router (192.168.100.1) even the internal.
Thats why it becomes very slow when the router goes down. But at least internal trafic should not pass through that router. The internal trafic should be routed by linux server it self.
Please can any body tell me how to configure gateway in linux in this senrio.
My requirement is the Linux should be able to send mail to yahoo and others. But the Linux server should not become slow when DSL internet connection goes down.

 

[marsd]

Nameservice is the answer. Try the same telnet connection(why are you using telnet..it's broken, unfixable unencrypted and exploitable),by address and you will see that 'speeds' things up.

It has nothing to do with routing.
Your routing explanation makes me wince by the way.
Please pick up a copy of Linux Routers by Tony Mancill,
you'll thank me later!

HTH

 

[fdalmoro]

Try setting up the Linux box as an internal DNS server. That should eliminate the mail server trying to look to an external DNS server, it should also speed-up mail delivery.

PS Referring to marsd's comment on Telnet, you should switch to SSH. Even though you are telnetting internally which doesn't sound too risky, it's a good habit to get into . Besides, if you want to get to your server from your favorite vacation spot when it has a problem, you want to make sure SSH is working.

Have fun

Fernando