Examples for setting up a network concentrator

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest

An example of a network environment with a network concentrator.

Figure 1 shows a network environment where a Linux® instance C acts as a network concentrator that connects other operating system instances on a HiperSockets LAN to an external LAN.

Figure 1. HiperSockets network concentrator setup
This graphic is described in the surrounding text.
Setup for the network concentrator C:
The HiperSockets interface enca1c0 (you can infer the interface name from the device bus-ID 0.0.a1c0) has IP address 10.20.30.51/24. The default gateway is 10.20.30.1.
Issue: 
# echo primary_connector > /sys/bus/ccwgroup/drivers/qeth/0.0.a1c0/route4

The OSA-Express CHPID in QDIO mode interface enca1c4 has IP address 10.20.30.11/24. The default gateway is 10.20.30.1.

Issue: 
# echo multicast_router > /sys/bus/ccwgroup/drivers/qeth/0.0.a1c4/route4
To enable IP forwarding issue: 
# sysctl -w net.ipv4.ip_forward=1
To remove the network routes for the HiperSockets interface issue: 
# ip route del 10.20.30/24
To start the HiperSockets network concentrator, run the script start_hsnc.sh. Issue: 
# start_hsnc.sh &
Setup for G:
No special setup required. The HiperSockets interface has IP address 10.20.30.54/24. The default gateway is 10.20.30.1.
Setup for workstation:
No special setup required. The network interface IP address is 10.20.30.120/24. The default gateway is 10.20.30.1.

Figure 2 shows the example of Figure 1 with an additional mainframe. On the second mainframe a Linux instance D acts as a HiperSockets network concentrator.

Figure 2. Expanded HiperSockets network concentrator setup
This graphic is described in the surrounding text.

The configuration of C, G, and the workstation remain the same as for Figure 1.

Setup for the network concentrator D:
The HiperSockets interface enca1d0 has the corresponding device bus-ID 0.0.a1d0 and IP address 0.0.0.0. Issue: 
# echo primary_connector > /sys/bus/ccwgroup/drivers/qeth/0.0.a1d0/route4

The OSA-Express CHPID in QDIO mode interface enca1d1 has IP address 10.20.30.50/24. The default gateway is 10.20.30.1.

D is not configured as a multicast router, it therefore only forwards unicast packets.

To enable IP forwarding issue: 
# sysctl -w net.ipv4.ip_forward=1
Tip: See the Red Hat documentation website for information about using configuration files to automatically enable IP forwarding when Linux boots:
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9
To start the HiperSockets network concentrator, run the script start_hsnc.sh. Issue: 
# start_hsnc.sh &
Setup for H:
No special setup required. The HiperSockets interface has IP address 10.20.30.55/24. The default gateway is 10.20.30.1.