I'm trying to fix a DNS issue that I've been having lately. I am running Fedora 11 behind my DSL router. I have the gateway and DNS server both set to the IP of the router. Seemed to work fine, but lately I noticed some problems. Sendmail is unable to resolve the domain name of my outbound email server (I'm using a smarthost). Also, telnet can not resolve any domain names. Neither sendmail nor telnet seem to be able to resolve ANY domain name. I am able to use Firefox just fine though, so I know that DNS must be working. Any ideas?

Strace may give you a clue, why things aren't working. Maybe a broken lib or nscd acting up or even a transient issue.

I have resolved the problem. Somehow, the NetworkManager service was causing problems. I am running this machine with a static IP, so I uninstalled the service. Everything seems to be working just fine now!