Configure IP Routing Globally or for a VRF

Configure the IP routing protocol stack to specify which routing features the device can use. You can configure global parameters before or after you configure the routing protocols.

About this task

To configure IP routing globally for a VRF instance, use VRF Router Configuration mode rather than Global Configuration mode.

Procedure

Enter either Global Configuration mode or VRF Router Configuration mode for a specific VRF context:

enable

configure terminal

Optional: router vrf WORD<1-16>
Configure the default TTL for all routing protocols to use:

ip ttl <1-255>

This value is placed into routed packets that have no TTL specified.
Activate the alternative route feature globally:

ip alternative-route
Configure the remaining global parameters as required.

Variable Definitions

The following table defines parameters for the ip command.


Variable	Value
alternative-route	Enables or disables the alternative route feature. The default value is enabled. If the alternative-route parameter is disabled, all existing alternative routes are removed. After you enable the parameter, all alternative routes are readded. The default form of this command is `default ip alternative-route`. The no form of this command is `no ip alternative-route`.
max-routes-trap enable	Enables the device to send a trap after the maximum number of routes is exceeded. The no form of this command is `no max-routes-trap enable`. The default form of this command is `default max-routes-trap enable`.
more-specific-non-local-route	Enables the more-specific-non-local-route feature. If enabled, the device can enter a more-specific nonlocal route into the routing table. The default is disabled. The default form of this command is `default ip more-specific-non-local-route`. The no form of this command is `no ip more-specific-non-local-route`.
routing	Enables routing. The no form of this command is `no ip routing`.
supernet	Enables or disables supernetting. If you globally enable supernetting, the device can learn routes with a route mask of less then eight bits. Routes with a mask length less than eight bits cannot have ECMP paths, even if the ECMP feature is globally enabled. The default is disabled. The default form of this command is `default ip supernet`. The no form of this command is `no ip supernet`.
ttl `<1-255>`	Configures the default time-to-live (TTL) value for a routed packet. The TTL is the maximum number of seconds before a packet is discarded. The default value of 255 is used whenever a time is not supplied in the datagram header. The default form of this command is `default ip ttl`.

The following table defines parameters for the ip icmp commands.


Variable	Value
unreachable	Enables the device to send ICMP unreachable messages. When enabled, this variable generates Internet Control Message Protocol (ICMP) network unreachable messages if the destination network is not reachable from this router. These messages help determine if the device is reachable over the network. The default is disabled. The default form of this command is `default ip icmp unreachable`.