Set attributes in the networks table

  1. Display the network settings defined in the xCAT networks table using: tabdump networks


    A default network is created for the detected primary network using the same netmask and gateway. There may be additional network entries in the table for each network present on the management node where xCAT is installed.

  2. To define additional networks, use one of the following options:

    • [Recommended] Use mkdef to create/update an entry into networks table.

      To create a network entry for 192.168.X.X/16 with a gateway of

      mkdef -t network -o net1 net= mask= gateway=
    • Use the tabedit command to modify the networks table directly in an editor:

      tabedit networks
    • Use the makenetworks command to automatically generate a entry in the networks table:

  3. Verify the network statements

    Domain and nameserver attributes must be configured in the networks table or in the site table for xCAT to function properly.

Initialize DHCP services

Configure DHCP to listen on different network interfaces [Optional]

The default behavior of xCAT is to configure DHCP to listen on all interfaces defined in the networks table.

The dhcpinterfaces keyword in the site table allows administrators to limit the interfaces that DHCP will listen over. If the management node has 4 interfaces, (eth0, eth1, eth2, and eth3), and you want DHCP to listen only on “eth1” and “eth3”, set dhcpinterfaces using:

chdef -t site dhcpinterfaces="eth1,eth3"

To set “eth1” and “eth3” on the management node and “bond0” on all nodes in the nodegroup=”service”, set dhcpinterfaces using:

chdef -t site dhcpinterfaces="eth1,eth3;service|bond0"

or, to explicitly identify the management node with hostname xcatmn:

chdef -t site dhcpinterfaces="xcatmn|eth1,eth3;service|bond0"


For the IBM OpenPOWER S822LC for HPC (“Minsky”) nodes, the BMC and compute “eth0” share the left-side integrated ethernet port and compute “eth1” is the right-side integrated ethernet port. For these servers, it is recommended to use two physical cables allowing the BMC port to be dedicated and “eth1” used by the OS. When an open range is configured on the two networks, the xCAT Genesis kernel will be sent to the BMC interface and causes problems during hardware discovery. To support this scenario, on the xCAT management node, if “eth1” is connected to the BMC network and “eth3” is connected to the compute network, disable genesis boot for the BMC network by setting :noboot in dhcpinterfaces using:

chdef -t site dhcpinterfaces="eth1:noboot,eth3"

# run the mknb command to remove the genesis
# configuration file for the specified network
mknb ppc64

For more information, see dhcpinterfaces keyword in the site table.

After making any DHCP changes, create a new DHCP configuration file with the networks defined using the makedhcp command.

makedhcp -n