After enabling path MTU discovery, how can I display the MTU discovered for an EE connection?

Technote (FAQ)


Question

Once I have PATHMTU running correctly is there some sort of display that I can see showing what it discovered for my EE connection? I guess I am looking for some sort of display similar to a trace route showing the path it took and the MTU it discovered along the way to make its adjustments.

Answer

See the information here on using the PING command to display MTU: the section "Determine the path MTU size to a host" in topic 1.4.7.1 "Using the Ping Command" of the z/OS Communications Server IP Diagnosis book.

An example of using the TSO PING command with PMTU yes is found in the IP System Administrator's Commands book.

An example of using the z/OS UNIX ping command with -P yes is also found in the IP System Administrator's Commands book.

In the "Determining the maximum transmission unit" section of the IP Configuration Guide, see this statement: "For an active link or interface, TCP/IP reports the interface MTU value in the ActMtu field of the Netstat DEVLINKS/-d report."

The syntax of the command to be used is :

    D TCPIP,tcpprocname,NETSTAT,DEV


The above command will show characteristics of all interfaces.

To limit the display to a single interface, use this command:
    DISPLAY TCPIP,tcpprocname,NETSTAT,DEV,INTFN=interface_name

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Document information


More support for:

z/OS Communications Server

Software version:

1.11, 1.12, 1.13, 2.1

Operating system(s):

z/OS

Reference #:

1596740

Modified date:

2012-12-06

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