Because there isn’t a rDNS entry (a PTR record) for your IP address. Are you expecting one to exist?

Tom

doesnt very one have a host ? Im new here

doesnt very one have a host ?

More or less, yes. But only a relative few need to register hosts in a DNS server.

Tom

ok thanks Tom I was concerned about whether not being able to rdns was a security problem

thanks for the replies but Im still none the wiser .Never mind Im just being paranoid

thanks for the replies but Im still none the wiser .

To keep things simple, there are a couple categories of systems in networks — some systems are servers and other systems are not servers.

Servers expect other systems to connect to them. But most systems don’t expect anything to connect to them; they generally only start connections out-bound. An e-mail server expects and accepts connections coming in to it. But your PC doesn’t want other systems connecting to it to deposit e-mail in it; it wants to connect to a server and to request e-mail.

The machines let all of the connections work by address. However, we humans want to work with names instead of addresses. DNS servers help machines translate names into addresses.

If you had a server named MYSERVER.MREE1.NET, you would have an IP address for it. If we knew the address, you could let us connect to it. And if you put your server’s name and address into a DNS server, we might be able to connect to it by using its name instead of having to remember its address. When we entered the name, the machine would send out a DNS request to see if it could get the name translated to an address and it would use the address to connect.

But if you never registered your server with DNS, we would couldn’t use MYSERVER.MREE1.NET to make a connection. We would have to enter your server’s address. One minor way around that would be to put an entry in a hosts file on our own systems. A hosts table is like a mini-DNS that is only used by the machine that has the file.

There are a number of different kinds of records that you can register with DNS. One kind is a PTR record. That is used when someone wants to do a reverse DNS query. Most DNS queries are used to translate names to addresses. A reverse DNS query does the opposite — it translates an address into the registered name.

Various DNS records can help establish that a connection really comes from a reputable source. Records generally don’t just get put into DNS servers by anyone at any time. If you went through all of the steps to setup rDNS for one of your systems, you would probably remember it.

Tom