port 25 refused

[John Hearns]

On Wed, 2004-08-04 at 11:02, Paul wrote:
> Hi,
> 
> > I am from India and use Ethernet based connectivity (which breaks
> > frequently) from a cable ISP who provides a private ip address
> > 172.16.x.x and masqed outbound connectivity.
> 
> That is really wierd! We have a vpn for a section of Salford Uni with an
> IP address of 172.16.x.x and it's completely useless (IMO)

> According to whois though, it's owned by ICANN for private purposes so
> shouldn't be allocated to anyone!

There are three ranges of 'non-routable' IP addresses, for use within
private networks.
10.0.0.0 to 10.255.255.255  Class A's
172.16.0.0 to 172.31.255.255 Class B's
192.168.0.0 to 192.168.255.255 Class C's

This chap's ISP has chosen the 172.16 network for his cable segment,
and as he says is using NAT to route the traffic out to the world.
Salford Uni can equally use the same block - it doesn't 'belong' to
them.

These ranges must only be used on private (internal) networks.

That's why you often see people on small/home  networks referring to
"192.168.x.x" IP ranges. Home routers often allocate 192.168 addresses.

You can use the private ranges for setting up test networks on the
bench, etc, etc.