Every day after work hours, we turn off our ADSL modem. When this happens, our normally okay Linux servers will respond slowly when we ssh or telnet to them. Likewise, some daemons, such as ntpd, will not able to sync time even with our internal servers. It seems to me this problem is caused by Linux still try to query external DNS servers although we are already using internal IP addresses.
When I remove all DNS settings inside resolve.conf, this problem goes away. However, we do need working resolve.conf.
What should I do? Thanks.