Specifications

Chapter 10. LAN notes 109
Figure 10-1 Small hub or router usage
The Network Address Translation function in the router allows your machine to work with fixed
IP addresses (provided by the NAT router).
5
These are typically in the 192.168.xxx.xxx range.
The router, in turn, works with variable DHCP addresses provided by your external network. If
NAT is not required, the router in the illustration can be changed to a simple hub. (The hub
option assumes the LAN connection can operate with a hub; this is not always the case and
you may need help from your network administrators to determine the best configuration.)
We specified the base router IP address (192.168.0.1) as the default gateway address in our
TCP/IP definitions (for both Linux and z/OS). For a multiuser system we connected additional
PCs to the router (which supplied its own range of DHCP addresses, if requested). The
additional PCs can connect to aws3270 (using the Linux IP address and port 3270) or to OSA
(using the IP address assigned, specified in the z/OS TCP/IP PROFILE).
Most routers can be configured to pass incoming port connections to specific local IP
addresses. This requires some work with the router software, but allows the handling of
incoming connections to z/OS (coming from a DHCP-based external network).
10.8 Shared Ethernet adapters
Scenario 4, in the LAN descriptions in the second volume of these books, uses a single “real”
Ethernet adapter (eth0, in the base Linux) for both Linux and z/OS. Some users find this
confusing. Figure 10-2 on page 110 illustrates this usage in more detail.
5
The router might also function as a DHCP server, providing DHCP addresses in a portion of its address range.
1090
machine
Other PCs for
x3270 or PCOM
sessions
Fixed IP addresses DHCP address
Multiple LAN adapters, if needed
LAN connection
"in the office wall"
Router with NAT
function