To configure a caching nameserver on a iRedMail server itself.
Reduces the delay in domain name resolution drastically as the requests for frequently accessed domain are served from cache.
"named" gets a request for domain resolution.
It checks whether the request can be satisfied from cache. If the answer is in cache and not stale, the request is satisfied from cache itself saving a lot of time
If request can't be satisfied from cache, named queries the first parent. If it replies with the answer, then named will cache the response and subsequent requests for the same domain name will be satisfied from the cache.
In case first parent fails to reply, named will query the second parent and so on.
How to install
We choose BIND which is the most common package on DNS server.
To check the package present or not on the system, just using
rpm -qa |grep bind rpm -qa |grep caching-nameserver
by default on iRedMail server, the result is:
[root@mail ~]# rpm -qa |grep bind ypbind-1.19-12.el5 bind-libs-9.3.6-4.P1.el5_4.2 bind-utils-9.3.6-4.P1.el5_4.2
the package we need on cache named server is
bind bind-chroot bind-util caching-nameserver
If its not present on your system, install using
yum install caching-nameserver bind-chroot
all the components we need will be installed