Re: dual IP

[mpradhan@healthnet.org.np]

Dear Brian Candler,

Yes, you are right. I have written mistake. It should be:
telnet 192,168.0.1 25
telnet 192.168.0.1 110

The dual IP seems working but the problem is as follows:

If I use the valid IP in the IP address part of workstation for example:
IP address: 202.52.231.197
Subnet mask 255.255.255.224

then I can not telnet with the private IP(192.168.0.1) but I can telnet 
with valid IP . Earlier I could telnet with private IP even if I have put 
valid IP in the IP part of network neighborhood of workstation.

If I use the private IP in the IP address part of workstation for 
example:

IP address: 192.168.0.6
Subnet mask: 255.255.255.0

Here, I can telnet both with private IP and valid up in the server 
whose valid IP is 202.52.231.194 and private IP is 192.168.0.1

Kindly let me know where I have done wrong.

With regards,

Sincerely yours,

Mohan Raj Pradhan
HealthNet Nepal



Date sent:      	Sat, 19 May 2001 10:10:22 +0100
From:           	Brian Candler <B.Candler@pobox.com>
To:             	mpradhan@healthnet.org.np
Copies to:      	tcpws@psg.com
Subject:        	Re: dual IP

> On Sat, May 19, 2001 at 06:56:53AM +0530, mpradhan@healthnet.org.np
> wrote: > I am using both Public IP 202.52.231.194 and Private IP >
> 192.168.0.1.  In the Private I can ping but cannot telnet as well as 
> > ping to port 25 i.e ping  192.168.0.1 25 and  to port 110 i.e. ping
> > 192.168.0.1. Earlier I could do telnet as well as ping to port 25
> and > 110 through private IP.
> 
> I think you are getting a little confused.
> 
> 'ping' sends an ICMP echo-request and the far end returns an ICMP
> echo-response. There is no port number involved. Port numbers apply to
> TCP and UDP only. So "ping 192.168.0.1 25" is meaningless. In fact, on
> my Linux laptop, that makes it try to ping 0.0.0.25 (which is a
> non-existent IP address and of course fails). On FreeBSD it gives a
> syntax error.
> 
> So the valid things to try are:
> 
> - ping 192.168.0.1           (can I send ICMP echo-request to this
> address
>                               and get an ICMP echo-response back?)
> 
> - telnet 192.168.0.1 25      (can I connect to TCP port 25 on this
> machine,
>                               i.e. the SMTP daemon?)
> 
> Regards,
> 
> Brian.