Cisco Systems 78-11741-02 manual Verifying Server Failure Detection, IPC-149

Configuring Server Load Balancing

IOS SLB Configuration Task List

h.Restart the connection, after waiting no longer than the sticky timeout value.

i.Enter the show ip slb conns EXEC command again.

j.Examine the real server connection counts again, and verify that the sticky connection is assigned to the same real server as before.

Step 6 Start additional client connections.

Step 7 Enter the show ip slb reals detail EXEC command.

Step 8 Verify that the the connection counts are increasing.

Verifying Server Failure Detection

To verify that server failures are detected correctly, perform the following steps:

Step 1 Use a large client population. If the number of clients is very small, tune the numclients keyword on the faildetect SLB real server configuration command so that the servers are not displayed as failed.

Step 2 Enter the show ip slb reals detail EXEC command to show the status of the real servers. Step 3 Examine the status and connection counts of the real servers:

•Servers that failed show a status of failed, testing, or ready_to_test, based on whether IOS SLB is checking that the server came back up when the command was sent.

•When a real server fails, connections that are assigned but not established (no SYN or ACK is received) are reassigned to another real server on the first inbound SYN after the reassign threshold is met. However, any connections that were already established are forwarded to the same real server because, although it may not be accepting new connections, it may be servicing existing ones.

•For weighted least connections, a real server that has just been placed in service starts slowly so that it is not overloaded with new connections. (See the “Slow Start” section for more information on this feature.) Therefore, the connection counts displayed for a new real server show connections going to other real servers (despite the lower count of the new real server). The connection counts also show “dummy connections” to the new real server, which IOS SLB uses to artificially inflate the connection counts for the real server during the slow start period.

Cisco IOS IP Configuration Guide

IPC-149