Riverstone Networks WICT1-12 - Manual (Page 476)

20-4 Riverstone Networks RS Switch Router User Guide Release 8.0
Configuring IP Policies IP Policy-Based Forwarding Configuration
Verifying Next-Hop Gateways
The
ip-policy set pinger on
command can be used to check the availability of next-hop gateways by
periodically querying them with ICMP_ECHO_REQUESTS. Only gateways that respond to these requests are used
for forwarding packets. For example, the following command checks the availability of next-hop gateways specified
in the policy ‘p1’:
Note Some hosts may have disabled responding to ICMP_ECHO packets. Make sure
each next-hop gateway can respond to ICMP_ECHO packets before using this
option.
When the
ip-policy set pinger on
command is issued, the RS can verify the state of a next-hop gateway by
sending a ping to the gateway at 5-second intervals. If the RS does not receive a reply from a gateway after four ping
requests, the gateway is considered to be “down.”
If you specify that the RS use TCP connection requests to check the gateway (instead of sending ICMP echo requests),
the RS checks that an application session on the gateway can be established by sending a TCP connection request on
the configured port of the gateway at 15-second intervals. If the RS does not receive a reply from the gateway after
four tries, the application is considered to be “down.”
You can change the intervals at which pings or handshakes are attempted and the number of times that the RS retries
the ping or handshake before considering the gateway or application to be “down.”
For example, the following commands cause the RS to check the availability of next-hop gateways for the IP policy
‘p1’ by pinging every 10 seconds:
You can also have the RS verify the content of an application on one or more next-hop gateways. For this type of
verification, you specify the following:
• A string that the RS sends to a single gateway or to a group of next-hop gateways. The string can be
a simple HTTP command to get a specific HTML page. Or, it can be a command to execute a
user-defined CGI script that tests the operation of the application.
• The reply that the application on each gateway sends back that the RS will use to validate the content.
In the case where a specific HTML page is retrieved, the reply can be a string that appears on the
page, such as “OK.” If a CGI script is executed on the gateway, it should return a specific response
(for example, “OK”) that the RS can verify.
rs(config)# ip-policy p1 set pinger on
rs(config)# ip-policy p1 set pinger on
rs(config)# ip-policy set pinger-options p1 ping-int 10