On Wednesday, 11/11/2009 at 08:23 EST, "Frank M. Ramaekers" 
<framaek...@ailife.com> wrote:

> 
> In other words:
> 
> VSWITCH               ETH0
> 10.1.20.2 <-------> 10.1.20.20 <-----> Everything else
> z/VSE                z/VM
> \
>  \
> Everything else

I am going to chastise myself (yet again) for dealing with a configuration 
problem without requiring the picture FIRST.  Strange as it sounds, your 
picture is not valid or you aren't understanding VSWITCHes.

Whenever a host touches a network of any sort (LAN or point-to-point), an 
IP address comes into existence.  (Special dispensation given for 
unnumbered IP interfaces, which z/VM TCP/IP doesn't support.)  If the two 
networks are not bridged by something outside of the hosts, then they are, 
by definition, separate networks.  Every network gets its own subnet, even 
if if contains only two hosts.  And within Subnet A, you never assign the 
IP addresses belonging to Subnet B.  Never.

In your drawing, I detect two networks:
1.  A network labeled "Everything else" (10.1.0.0/16)
2.  A network that has no label and no assigned subnet

You cannot communicate on Network 2 until you assign it a subnet that is 
not within 10.1.0.0/16, and then assign IP addresses within that new 
subnet.

If you simply trying to attach VM TCP/IP and z/VSE to a VSWITCH, the 
picture looks like

 10.1.20.2            10.1.20.20
    | ETH0                | ETH0  (vNICs)
--------------VSWITCH------------
      OSA |   The VSWITCH is
          |   an ethernet bridge 
---Real network------------------ 10.1.0.0/16

They can talk to each other and out to the network.

Alan Altmark
z/VM Development
IBM Endicott

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