Re: help

[Tzafrir Cohen <tzafrir@technion.ac.il>]

On Sat, 8 Dec 2001, [gb2312] ????³? wrote:

> Hello.
> I have question about DNS.I want to know reverse DNS role.

Generally: read the networking-concepts HOWTO and the DNS-HOWTO. The
DNS-HOWTO is generally intended for setting up a simple DNS server,
however it contains useful explanations on how the DNS system works.

> When I input
> a IP address,DNS will return the IP's relevent domain,what role of this
> function in DNS?

The DNS database also includes a separate database of all the IP addresses
(registrated ones, that is).

To allow  efficient resolving of IP addresses to DNS names, the registered
IP addresses are registered in their own zones.

50.100.150.200 is registered in the following DNS entry:

200.150.100.50.in-addr.arpa

For more details, see the above documentation

> My second question whether adverse DNS is related with
> firewall,if has,what is it?Any ideas will be appreciated.

Everything that is releated to networking is also realted to "firewall".
"firewall" is a vague" concept. Even if you mean something like
"ipchains/iptables script" then you also have to consider DNS packets that
go through the packet-filtering firewall.

In short: be more specific.

-- 
Tzafrir Cohen
mailto:tzafrir@technion.ac.il
http://www.technion.ac.il/~tzafrir