nslookup does not work correctly across vlans
Posted on 2008-11-03
We are having some issues with DNS but I am not sure where the problem is. We noticed it while doing nslookups. We have multiple vlans. Our servers reside on the 10.3.x.x subnet. Our desktops are on 10.8.x.x. Here is the scenario:
1) When doing an nslookup to resolve dns name to IP address it works everytime from every subnet. For example: nslookup "servername" returns the correct IP address. This works from a server on the 10.3.x.x trying to resolve a 10.3.x.x or a 10.8.x.x. It also works from a desktop on the 10.8.x.x trying to resolve a 10.3.x.x. or a 10.8.x.x.
2) When doing an nslookup to do a reverse lookup (give it an IP and return a dns name) it works going from a 10.3.x.x to a 10.3.x.x or a 10.8.x.x to a 10.3.x.x. For example: nslookup 10.3.1.254 returns "servername.domain.com"
3) When doing an nslookup to do a reverse lookup it does NOT work going from a 10.3.x.x to a 10.8.x.x or from a 10.8.x.x to a 10.8.x.x. When we type nslookup 10.8.99.101 for example we get this response:
*** <one of our DNS servers>.domain.com can't find 10.8.99.101: Non-existent domain
So to summarize doing dns to IP works across all vlans. Doing IP to dns only works when the dns name you are looking for resides on the vlan on which our dns servers reside. Doing IP to dns does not work when the dns name you are looking for resides on a vlan other than the one that the DNS servers reside on.
Any ideas as to what could be going on and how to resolve it? Thanks!