Cisco Systems OL-4580-01 manual Disabling an Implicit Service for the Static Route Next Hop

Chapter 6 Configuring the Internet Protocol

Disabling an Implicit Service for the Static Route Next Hop

Disabling an Implicit Service for the Static Route Next Hop

By default, the CSS establishes an implicit (or internal) service for the gateway address when a static route is defined. When you do not want the CSS to start an implicit service for the next hop of a static route, use the ip no-implicit-servicecommand. The ip no-implicit-servicecommand specifies that no implicit service is established to the next hop of the static route, which disables the internal service ICMP keepalive. In this case, if the ARP address for the next hop is not known to the CSS, the address will not appear in the routing table.

The purpose of the implicit service to the next hop of a static route is to monitor the availability of the next hop to forward data traffic. When the ip no-implicit-servicecommand is in effect, traffic is forwarded to the next hop even when the next hop is unavailable. Because of the possibility of data being lost if the next hop becomes unavailable, use of the ip no-implicit-servicecommand is strongly discouraged.

Note Static routes can sometimes appear in the CSS routing table even when you have an implicit service for the next hop address (the default setting) and the internal keepalive is down. When the CSS detects the ARP mapping for the next hop in the static route, the CSS continues to list that route in the routing table regardless of the state of the ICMP service keepalive (Down or Up).

When you implement the ip no-implicit-serviceglobal configuration command, this action does not affect previously configured static routes. The ip no-implicit-servicecommand affects only those static routes added after you enable the command. We recommend you reboot the CSS after you modify the configuration to ensure all static routes are the same, which is useful for network monitoring and troubleshooting. If you wish to stop the implicit service for a previously configured static route, then you must delete and reconfigure the static route.

For example:

(config)# ip no-implicit-service

To reset the default setting, enter:

(config)# no ip no-implicit-service

	Cisco Content Services Switch Routing and Bridging Configuration Guide
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