Hi Simone, what nameservers are configured for the nfs-servers? Afaict the nfs-server does forward and reverse lookup the clients. So if your nfs-server's DNS breaks (i.e. if only ns0 is configured there and you shut down ns0) you might see the issue you described. Regards, Andreas Simone schrieb: > Hi all, > > Today we have had a strange problem that has taken down our website, we > understand what happened but not why so I am hoping someone has seen > this before. > > We have our web servers (web1 web2 web3 ..... web10) mounting an NFS > share (/export/data) from server nfs1. On the web server side we use > autofs in the format nfs-dedicated:/export/data where nfs-dedicated is > an alias in our internal DNS servers pointing to server nfs1. We run a > primary and a secondary DNS (bind) server ns0, ns1 authoritative for our > zones and our webservers have them configured in /etc/resolv.conf > Today we had to run some upgrade on the dns servers (bios firmwares etc) > so we took down ns0 and with it our website went down. > All the nfs shares disappeared from the web servers (the logs show > requests to mount/unmount timing out), but at the same time on nfs1 the > logs show requests (mount and unmount) coming from the web servers and > no errors. > > As soon as ns0 is back up, all gets back to normal. Minutes later we > take down ns1 for maintenance and it doesn't have any impact on the > website. > > dig @ns0 nfs-web gives exactly the same results on ns0/1 > > Back to the office we try to reproduce the same scenario configuring > iptables on web3 to block traffic to ns0 but the server (web3) keeps > working fine reverting to ns1 for name resolution (as you would expect). > > Has anybody seen this happening before? Any comment/suggestion much > appreciated. > > Thanks > > Simone > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >