Network Instruments 114ff manual TCP/IP ports, Nat

This section discusses the TCP/IP ports, NAT, and VPN.

TCP/IP ports

Observer and all Network Instruments probes use ports 25901 and 25903 to communicate. These ports are registered ports to Network Instruments.

All Network Instruments probes initiate connection with Observer using port 25901. Observer listens on port 25901. After a connection is established all communication between Observer and the probes occurs on port 25901, except probe redirection and administration, which uses port 25903.

Figure 85 Port connections

	Port 2	redirection request	Port
			25903
	5	request approved	25901
	9
		connection request
	0			Any Probe
		connection established	25901
Observer Console	1
NAT

If you use network address translation (NAT) in your environment, you must make some configuration changes in Observer. Using the TCP/IP port information in “TCP/IP ports” on page 124, you should be able to set up the NAT properly.

If the probe is outside the network where Observer is running, you must forward port 25901 from the probe’s address to the system running Observer.

When redirecting the probe, you must specify the NAT outside IP address instead of the address that Observer puts in automatically. By default, Observer tries to use its local IP address, which the probe will not be able to find. Select “Redirect to a specified IP address” in the Redirecting Probe or Probe Instance dialog (Figure 86).

124 TCP/IP ports

Appendix A TCP/IP ports, NAT, and VPN rev. 1