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Default Gateway Is Lost After the CTDB Node Is Restarted

Publication Date:  2014-09-22 Views:  87 Downloads:  0
Issue Description
•Product involved: CSS-F
•Product version: CSS-F V001R001C01
•Application scenario: NFS service application
The SUSE 10 operating system and NFS service provided by the CTDB are in use. After the CTBD node restarts, services are interrupted and the NFS client cannot connect to the external public IP address provided by the NFS server.

Alarm Information
None

Handling Process
1.Run the vi /etc/ctdb/static-routes command to add a default gateway for the CTDB floating IP address after the CTDB service is restarted.
bond0 0.0.0.0/0 192.168.82.254
NOTE:
Normally, the routing port for the default gateway is set to bond0 of the OSN node.


After the CTDB floating IP address is loaded, the static route specified in the command is loaded and set to the default gateway. Then the default gateway loss problem is resolved.

This method is applicable to the default gateway loss problem occurred after both the network service and CTDB node are restarted or the network service is restarted but the CTDB node is not.

Root Cause
The gateway loss is caused by the current IP address configuration. The IP addresses in use are configured as follows: The CSS service IP address exclusively occupies a network segment and the NFS floating IP address and default gateway reside on the same network segment.

The routing table is as follows before the CTDB node restart:

Destination        Gateway       Genmask
192.168.86.0         0        255.255.255.0      Service IP address, used only within the CSS
192.168.82.0         0        255.255.255.0      Floating IP address, started by the CTDB service
127.0.0.0            0           255.0.0.0                Lo IP address
0                192.168.82.254      0                  Default gateway

In the preceding routing table, the service IP address used within the CSS resides on network segment 192.168.86.*, which is for CSS internal use only. The floating public IP address residing on network segment 192.168.82.* is used by the CTDB service to connect the NFS service to the external NFS client. 192.168.82.254 is used as the default gateway to provide the NFS service.

Normally, after a node is restarted, the network service is loaded in the sequence of physical interface, virtual IP address (ifcfg-*), Lo IP address, VLAN..., route gateway, and CTDB floating IP address. In this case, after the CTDB node is restarted, the network service is loaded in the sequence of service IP address residing on 192.168.86.*, Lo IP address, and default gateway. However, the default gateway failed to be loaded because the CTDB floating IP address is not loaded. The CTDB floating IP address residing on 192.168.82.* is loaded successfully only after the CTDB service is restarted. The routing table is as follows after the CTDB node restart:

Destination        Gateway       Genmask
192.168.86.0         0        255.255.255.0      Service IP address, used only within the CSS
192.168.82.0         0        255.255.255.0      Floating IP address, started by the CTDB service
127.0.0.0            0        255.0.0.0                Lo IP address

When the default gateway is lost (failed to be loaded), the NFS client cannot connect to the CTDB floating IP address, causing the service interruption.
Suggestions
The current CTDB IP addresses for external access are configured in either of following methods:

The CSS service IP address, NFS floating IP address, and default gateway reside on the same network segment. In this IP address configuration, the default gateway is not lost after the CTDB node restart.
The CSS service IP address exclusively occupies a network segment and the NFS floating IP address and default gateway reside on the same network segment. In this IP address configuration, the default gateway is lost after the CTDB node restart.
If the default gateway loss is caused by the second network configuration method, you can resolve the problem by adding the static route as the default gateway.

END