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Re: netstat ?



In <SNT125-W503AD2F570F2C86CE7A4AFDB410@phx.gbl>, Hadi Motamedi wrote:
>My Debian server is at @172.16.128.1 and the remote network element is at
> @172.16.4.1 , but the 'netstat' does not show the ip address and the
> assigned port from my Debian . It just shows many dedicated ports ,
> assigned with '0.0.0.0:xx' format . Can you please let me know how can I
> distinguish the dedicated port to that remote network element ?

There's not one.  That's not the way TCP/IP or UDP/IP servers work.  All the 
client connections use the same server IP address and port.  The TCP/IP or 
UDP/IP stack separates them into different connections based on the source 
address.  Netstat shows sockets, not connections.

In pictures (ASCII art, view in a fixed-width font):

             src = y.y.y.y:ry             src = z.z.z.z:rz
+----------+ dst = x.x.x.x:dx +---------+ dst = x.x.x.x:dx +----------+
| Client 1 |----------------->| Server  |<-----------------| Client 2 |
| y.y.y.y  |                  | x.x.x.x |                  | z.z.z.z  |
| port ry  |<-----------------| port dx |----------------->| port rz  |
+----------+ src = x.x.x.x:dx +---------+ src = x.x.x.x:dx +----------+
             dst = y.y.y.y:ry             dst = z.z.z.z:rz

There are a number of tools that can "look in" to the TCP/IP or UDP/IP stack 
and give you per-connection metrics.  I think iptraf is one of them; tcpdump 
can also be used.  Someone with more network monitoring experience will have
to mention any others.
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