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Full Discussion: reverse lookup for email
Special Forums IP Networking reverse lookup for email Post 45454 by Perderabo on Saturday 20th of December 2003 06:56:58 PM
Old 12-20-2003
Yes you would use the standard syntax.

If your current isp is doing your dns, it also has the reverse entries setup. Who will be doing your dns after you switch? Your new isp? If so it will need to set up the reverse entries.

Keep your eye on the prize. Anyone is the world needs to be able to take your fqdn and get your ip address. And anyone in the world needs to be able to take your ip address and get your fqdn. This means that anyone in the world needs to be able to contact your primary dns server and your secondary dns server. After the switch you will need these two internet visable boxes. Are you clear on that? Do they exist? You worry me with this talk about using a hosts file. Let's take an imaginary example and walk it though....

Now let's say that you're currently using Joe's ISP Service and you plan to switch to Steve's ISP service. And let's say that you have a box called mailguy.something.com with an IP address of 1.2.3.4 and you need to change that to 5.6.7.8.

Joe is running your current nameservers. So his nameservers are authoritative for all of something.com. And his nameserver's are authoritative for 1.2.3.4. So Joe can do both your forward and reverse entries for you.

Now Joe can enter your new forward entry. But Steve is authoritative for 5.6.7.8. Steve would need to do the reverse entry. If Steve does not do DNS, he could delegate the address to your nameservers. Then you could do the reverse. I suppose that Steve could delegate it to Joe too in theory, but that would be an odd thing to do.

But you need to get something.com off of Joe's nameservers. Joe would then continue to handle any reverse entries for Ip addresses that he owns. If you need to continue using Joe's nameservers after you switch to Steve's ISP service, Joe may charge a large fee or something.
 

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unbound(8)							   unbound 1.5.1							unbound(8)

NAME
unbound - Unbound DNS validating resolver 1.5.1. SYNOPSIS
unbound [-h] [-d] [-v] [-c cfgfile] DESCRIPTION
Unbound is a caching DNS resolver. It uses a built in list of authoritative nameservers for the root zone (.), the so called root hints. On receiving a DNS query it will ask the root nameservers for an answer and will in almost all cases receive a delegation to a top level domain (TLD) authoritative nameserver. It will then ask that nameserver for an answer. It will recursively continue until an answer is found or no answer is available (NXDO- MAIN). For performance and efficiency reasons that answer is cached for a certain time (the answer's time-to-live or TTL). A second query for the same name will then be answered from the cache. Unbound can also do DNSSEC validation. To use a locally running Unbound for resolving put nameserver 127.0.0.1 into resolv.conf(5). If authoritative DNS is needed as well using nsd(8), careful setup is required because authoritative nameservers and resolvers are using the same port number (53). The available options are: -h Show the version and commandline option help. -c cfgfile Set the config file with settings for unbound to read instead of reading the file at the default location, /usr/local/etc/unbound/unbound.conf. The syntax is described in unbound.conf(5). -d Debug flag: do not fork into the background, but stay attached to the console. This flag will also delay writing to the log file until the thread-spawn time, so that most config and setup errors appear on stderr. If given twice or more, logging does not switch to the log file or to syslog, but the log messages are printed to stderr all the time. -v Increase verbosity. If given multiple times, more information is logged. This is in addition to the verbosity (if any) from the config file. SEE ALSO
unbound.conf(5), unbound-checkconf(8), nsd(8). AUTHORS
Unbound developers are mentioned in the CREDITS file in the distribution. NLnet Labs Dec 8, 2014 unbound(8)
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