Multiple DHCP servers in a cluster

Troubleshooting multiple DHCP servers in a cluster.

You cannot have multiple DHCP servers that run on the same network. Multiple DHCP servers can cause provisioning to fail; nodes are unavailable and cannot be reached. To resolve this issue, identify the extra DHCP servers, shut down the extra DHCP servers, and reboot the nodes.

Using the command line, you can identity multiple DHCP servers in a cluster. To identify DHCP servers, use the xCAT detect_dhcpd tool that is provided in the /opt/xcat/share/xcat/tools directory. The detect_dhcpd tool can run on any node that is connected to the management node. To run the detect_dhcpd tool, issue the following command:

/opt/xcat/share/xcat/tools/detect_dhcpd -i network-NIC

where network-NIC is the name of your network interface configuration.

Examples

For example, if you have one DHCP server in a cluster, issue the following command:

# /opt/xcat/share/xcat/tools/detect_dhcpd -i eth1

where eth1 is the name of your network interface configuration.

As a result the tool provides the following information:

++++++++++++++++++++++++++++++++++
There are 1 servers reply the dhcp discover.
    Server:193.0.0.1 assign IP [193.0.0.204] to you. The next server is [193.0.0.1]!
++++++++++++++++++++++++++++++++++

For example, if you have two or more DHCP servers in a cluster, issue the following command:

# /opt/xcat/share/xcat/tools/detect_dhcpd -i eth1

where eth1 is the name of your network interface configuration.

As a result the tool provides the following information:

++++++++++++++++++++++++++++++++++
There are 2 servers reply the dhcp discover.
    Server:13.13.0.3 assign IP [13.13.0.203] to you. The next server is [13.13.0.3]!
    Server:193.0.0.1 assign IP [193.0.0.204] to you. The next server is [193.0.0.1]!
++++++++++++++++++++++++++++++++++