Reverse DNS and Subnets

[CHiLL]

We have multiple VLANs and some of them have been subnetted with either /29 or /30. However we've noticed that only the first 255 IP addresses in the subnet are logged in reverse DNS.

 

For example, we have a reverse lookup zone named "100.22.10.in-addr.arpa". This is for our subnetted VLAN100 at 10.22.100.0/30. This VLAN spans the IP ranges 10.22.100.1 to 10.22.103.255. Reverse DNS is only showing clients with IP addresses 10.22.100.1 to 10.22.100.254.

 

Any ideas how I can make the reverse lookup zone also work with the rest of the subnet?

[KevinB]

That seems to be expected behaviour, it has certainly done the same for me anytime I've used subnets larger than /24. For example we have a /22 for our main wired LAN, and in order to have reverse DNS working I have to create 4 separate reverse zones, one corresponding to each of the /24s inside the /22.

[CHiLL]

Thanks for the update. I need to clarify, we have multiple VLANs that are either /21 or /22 (not /29 or /30 as I put in my original post!).

 

I ended up creating a new reverse DNS zone for each segment of the /21 and /22 VLANs. I was hoping for an automatic way or something similar. Never mind!

[KevinB]

NP. I figured you'd just counted the wrong way