Question : RESERVE DNS

We're in a process of moving all our in house DNS servers to an outside provider to manage. We have 2 sites that we manage DNS addresses for. Which means a number of Reserve DNS records. Besides using Reverse DNS for emails, do we really need reverse DNS for anything else. Is it really necessary to have reverse DNS for all the records in the forward? If we only carried the reverse for email do we need the reverse for anything else? EX. do we really need a reserve for VPN?

Answer : RESERVE DNS

It's using a cached DNS server and that's fine.

If you want to query a 3rd party nameserver (such as OpenDNS) you can use the command as follows:

roachy@pr-laptop:~$ nslookup
> server 208.67.220.220
Default server: 208.67.220.220
Address: 208.67.220.220#53
> set type=ptr
> 64.156.32.251
Server:            208.67.220.220
Address:      208.67.220.220#53

Non-authoritative answer:
251.32.156.64.in-addr.arpa      name = dialup-64.156.32.251.Dial1.Denver1.Level3.net.

Note that the server command changes the default server - in my example I used opendns, but in your case you can use the authoritative server for the IP block.

The authoritative server for the IP block can be ascertained by doing a whois lookup - for EE as per my example you can see Level 3 Communications look after the reverse DNS (and the IP block) for Experts-Exchange:

 whois 64.156.132.251

OrgName:    Level 3 Communications, Inc.
OrgID:      LVLT
Address:    1025 Eldorado Blvd.
City:       Broomfield
StateProv:  CO
PostalCode: 80021
Country:    US

NetRange:   64.152.0.0 - 64.159.255.255
CIDR:       64.152.0.0/13
NetName:    LC-ORG-ARIN
NetHandle:  NET-64-152-0-0-1
Parent:     NET-64-0-0-0-0
NetType:    Direct Allocation
NameServer: NS1.LEVEL3.NET
NameServer: NS2.LEVEL3.NET
Comment:    ADDRESSES WITHIN THIS BLOCK ARE NON-PORTABLE
RegDate:    2000-06-08
Updated:    2001-05-30

Hope this helps!