Specifications

IP Switching Commands
ip route-cache
ISW-54
Cisco IOS IP Switching Command Reference
May 2008
On Cisco routers with Route/Switch Processor (RSP) and VIP controllers, the VIP hardware can be
configured to switch packets received by the VIP with no per-packet intervention on the part of the RSP.
When VIP distributed switching is enabled, the input VIP interface tries to switch IP packets instead of
forwarding them to the RSP for switching. Distributed switching helps decrease the demand on the RSP.
If the ip route-cache distributed, ip cef distributed, and ip route-cache flow commands are
configured, the VIP performs distributed Cisco Express Forwarding switching and collects a finer
granularity of flow statistics.
IP Route-Cache Cisco Express Forwarding
In some instances, you might want to disable Cisco Express Forwarding or distributed Cisco Express
Forwarding on a particular interface because that interface is configured with a feature that
Cisco Express Forwarding or distributed Cisco Express Forwarding does not support. Because all
interfaces that support Cisco Express Forwarding or distributed Cisco Express Forwarding are enabled
by default when you enable Cisco Express Forwarding or distributed Cisco Express Forwarding
operation globally, you must use the no form of the ip route-cache distributed command in the
interface configuration mode to turn Cisco Express Forwarding or distributed Cisco Express Forwarding
operation off a particular interface.
Disabling Cisco Express Forwarding or distributed Cisco Express Forwarding on an interface disables
Cisco Express Forwarding or distributed Cisco Express Forwarding switching for packets forwarded to
the interface, but does not affect packets forwarded out of the interface.
Additionally, when you disable distributed Cisco Express Forwarding on the RSP, Cisco IOS software
switches packets using the next-fastest switch path (Cisco Express Forwarding).
Enabling Cisco Express Forwarding globally disables distributed Cisco Express Forwarding on all
interfaces. Disabling Cisco Express Forwarding or distributed Cisco Express Forwarding globally
enables process switching on all interfaces.
Note On the Cisco 12000 series Internet router, you must not disable distributed Cisco Express Forwarding
on an interface.
IP Route Cache Policy
If Cisco Express Forwarding is already enabled, the ip route-cache route command is not required
because PBR packets are Cisco Express Forwarding-switched by default.
Before you can enable fast-switched PBR, you must first configure PBR.
FSPBR supports all of PBR’s match commands and most of PBR’s set commands, with the following
restrictions:
• The set ip default next-hop and set default interface commands are not supported.
• The set interface command is supported only over point-to-point links, unless a route cache entry
exists using the same interface specified in the set interface command in the route map.
Also, at the process level, the routing table is consulted to determine if the interface is on a
reasonable path to the destination. During fast switching, the software does not make this check.
Instead, if the packet matches, the software blindly forwards the packet to the specified interface.
Note Not all switching methods are available on all platforms. Refer to the Cisco Product Catalog for
information about features available on the platform you are using.