When problems arise with DAS servers, clients, or connectivity, there are a number of tools available to help you out.
You can use the following list as a guide:
- Verify IP connectivity
- Verify DNS resolution, DNS records, hostnames, and /etc/hosts entries
- Check firewalls and packetfilters, disable temporarily if necessary
- Make sure daemons are running and the appropriate ports are listening
- Check time synchronization
- Check logs on server or client
- Use a protocol analyzer (sniffer) like Ethereal to watch the network traffic
- Check your /etc/pam.d/ config files. These are especially error-prone.
- Use built-in diagnostic commands for Kerberos, NIS, RPC, and NTP.
- Sometimes shutting down NSCD on clients will help you isolate problems
Of course, make sure you have good config file backups before you start any intensive troubleshooting!
Final Question: Do you have a good network diagram? If not, why not?