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ip route-cache

To control the use of switching methods for forwarding IP packets, use the ip route-cache command in interface configuration mode. To disable any of these switching methods, use the no form of this command.

ip route-cache [cef | distributed | flow | policy | same-interface]

no ip route-cache [cef | distributed | flow | policy | same-interface]

Syntax Description

Defaults

The switching method is not controlled.

Command Modes

Interface configuration (config-if)

Usage Guidelines

IP Route Cache

Note The Cisco 10000 series routers do not support the ip route-cache command.

Using the route cache is often called fast switching. The route cache allows outgoing packets to be load-balanced on a per-destination basis rather than on a per-packet basis. The ip route-cache command with no additional keywords enables fast switching.

Entering the ip route-cache command has no effect on a subinterface. Subinterfaces accept the no form of the command; however, this disables Cisco Express Forwarding or distributed Cisco Express Forwarding on the physical interface and all subinterfaces associated with the physical interface.

The default behavior for Fast Switching varies by interface and media.

Note IPv4 fast switching is removed with the implementation of the Cisco Express Forwarding infrastructure enhancements for Cisco IOS 12.2(25)S-based releases and Cisco IOS Release 12.4(20)T. For these and later Cisco IOS releases, switching path are Cisco Express Forwarding switched or process switched.

IP Route Cache Same Interface

You can enable IP fast switching when the input and output interfaces are the same interface, using the ip route-cache same-interface command. This configuration normally is not recommended, although it is useful when you have partially meshed media, such as Frame Relay or you are running Web Cache Communication Protocol (WCCP) redirection. You could use this feature on other interfaces, although it is not recommended because it would interfere with redirection of packets to the optimal path.

IP Route Cache Flow

The flow caching option can be used in conjunction with Cisco Express Forwarding switching to enable NetFlow, which allows statistics to be gathered with a finer granularity. The statistics include IP subprotocols, well-known ports, total flows, average number of packets per flow, and average flow lifetime.

Note The ip route-cache flow command has the same functionality as the ip flow ingress command, which is the preferred command for enabling NetFlow. If either the ip route-cache flow command or the
ip flow ingress command is configured, both commands will appear in the output of the
show running-config command.

IP Route Cache Distributed

The distributed option is supported on Cisco routers with line cards and Versatile Interface Processors (VIPs) that support Cisco Express Forwarding switching.

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.

Examples

Configuring Fast Switching and Disabling Cisco Express Forwarding Switching

The following example shows how to enable fast switching and disable Cisco Express Forwarding switching:

Router(config)# interface ethernet 0/0/0 

Router(config-if)# ip route-cache 

The following example shows that fast switching is enabled:

Router# show ip interface fastEthernet 0/0/0    

FastEthernet0/0/0 is up, line protocol is up 

  Internet address is 10.1.1.254/24 

  Broadcast address is 255.255.255.224 

  Address determined by non-volatile memory 

  MTU is 1500 bytes 

  Helper address is not set 

  Directed broadcast forwarding is disabled 

  Multicast reserved groups joined: 224.0.0.10 

  Outgoing access list is not set 

  Inbound  access list is not set 

  Proxy ARP is enabled 

  Security level is default 

  Split horizon is enabled 

  ICMP redirects are always sent 

  ICMP unreachables are always sent 

  ICMP mask replies are never sent 

  IP fast switching is enabled 

  IP fast switching on the same interface is disabled 

  IP Flow switching is disabled 

  IP Distributed switching is disabled 

  IP Feature Fast switching turbo vector 

  IP Null turbo vector 

  IP multicast fast switching is enabled 

The following example shows that Cisco Express Forwarding switching is disabled:

Router# show cef interface fastEthernet 0/0/0 

  FastEthernet0/0/0 is up (if_number 3) 

  Corresponding hwidb fast_if_number 3 

  Corresponding hwidb firstsw->if_number 3 

  Internet address is 10.1.1.254/24 

  ICMP redirects are always sent 

  Per packet load-sharing is disabled 

  IP unicast RPF check is disabled 

  Inbound access list is not set 

  Outbound access list is not set 

  IP policy routing is disabled 

  Hardware idb is FastEthernet0/0/0 

  Fast switching type 1, interface type 18 

  IP CEF switching disabled 

  IP Feature Fast switching turbo vector 

  IP Null turbo vector 

  Input fast flags 0x0, Output fast flags 0x0 

  ifindex 1(1) 

  Slot 0 Slot unit 0 VC -1 

  Transmit limit accumulator 0x48001A02 (0x48001A02) 

  IP MTU 1500 

The following example shows the configuration information for interface fastethernet 0/0/0:

Router# show running-config 

. 

. 

! 

interface FastEthernet0/0/0 

 ip address 10.1.1.254 255.255.255.0 

 no ip route-cache cef 

 no ip route-cache distributed 

! 

The following example shows how to enable Cisco Express Forwarding (and to disable distributed
Cisco Express Forwarding if it is enabled):

Router(config-if)# ip route-cache cef 

The following example shows how to enable VIP distributed Cisco Express Forwarding and per-flow accounting on an interface (regardless of the previous switching type enabled on the interface):

Router(config)# interface e0 

Router(config-if)# ip address 10.252.245.2 255.255.255.0 

Router(config-if)# ip route-cache distributed 

Router(config-if)# ip route-cache flow 

The following example shows how to enable Cisco Express Forwarding on the router globally (which also disables distributed Cisco Express Forwarding on any interfaces that are running distributed
Cisco Express Forwarding), and disable Cisco Express Forwarding (which enables process switching) on Ethernet interface 0:

Router(config)# ip cef  

Router(config)# interface e0 

Router(config-if)# no ip route-cache cef 

The following example shows how to enable distributed Cisco Express Forwarding operation on the router (globally), and disable Cisco Express Forwarding operation on Ethernet interface 0:

Router(config)# ip cef distributed  

Router(config)# interface e0 

Router(config-if)# no ip route-cache cef 

The following example shows how to reenable distributed Cisco Express Forwarding operation on Ethernet interface 0:

Router(config)# ip cef distributed  

Router(config)# interface e0 

Router(config-if)# ip route-cache distributed 

Configuring Fast Switching for Traffic That Is Received and Transmitted over the Same Interface

The following example shows how to enable fast switching and disable Cisco Express Forwarding switching:

Router(config)# interface ethernet 0/0/0 

Router(config-if)# ip route-cache same-interface 

The following example shows that fast switching on the same interface is enabled for interface fastethernet 0/0/0:

Router# show ip interface fastEthernet 0/0/0   

FastEthernet0/0/0 is up, line protocol is up 

  Internet address is 10.1.1.254/24 

  Broadcast address is 255.255.255.224 

  Address determined by non-volatile memory 

  MTU is 1500 bytes 

  Helper address is not set 

  Directed broadcast forwarding is disabled 

  Multicast reserved groups joined: 224.0.0.10 

  Outgoing access list is not set 

  Inbound  access list is not set 

  Proxy ARP is enabled 

  Security level is default 

  Split horizon is enabled 

  ICMP redirects are always sent 

  ICMP unreachables are always sent 

  ICMP mask replies are never sent 

  IP fast switching is enabled 

  IP fast switching on the same interface is enabled 

  IP Flow switching is disabled 

  IP Distributed switching is disabled 

  IP Feature Fast switching turbo vector 

  IP Null turbo vector 

  IP multicast fast switching is enabled 

  IP multicast distributed fast switching is disabled 

  IP route-cache flags are Fast 

  Router Discovery is disabled 

  IP output packet accounting is disabled 

  IP access violation accounting is disabled 

  TCP/IP header compression is disabled 

  RTP/IP header compression is disabled 

  Probe proxy name replies are disabled 

  Policy routing is disabled 

  Network address translation is disabled 

  WCCP Redirect outbound is disabled 

  WCCP Redirect inbound is disabled 

  WCCP Redirect exclude is disabled 

  BGP Policy Mapping is disabled 

  IP multicast multilayer switching is disabled 

The following example shows the configuration information for interface fastethernet 0/0/0:

Router# show running-config 

. 

. 

! 

interface FastEthernet0/0/0 

 ip address 10.1.1.254 255.255.255.0 

 ip route-cache same-interface 

 no ip route-cache cef 

 no ip route-cache distributed 

! 

Enabling NetFlow Accounting

The following example shows how to enable NetFlow switching:

Router(config)# interface ethernet 0/0/0 

Router(config-if)# ip route-cache flow 

The following example shows that NetFlow accounting is enabled for interface fastethernet 0/0/0:

Router# show ip interface fastEthernet 0/0/0  

FastEthernet0/0/0 is up, line protocol is up 

  Internet address is 10.1.1.254/24 

  Broadcast address is 255.255.255.224 

  Address determined by non-volatile memory 

  MTU is 1500 bytes 

  Helper address is not set 

  Directed broadcast forwarding is disabled 

  Multicast reserved groups joined: 224.0.0.10 

  Outgoing access list is not set 

  Inbound  access list is not set 

  Proxy ARP is enabled 

  Security level is default 

  Split horizon is enabled 

  ICMP redirects are always sent 

  ICMP unreachables are always sent 

  ICMP mask replies are never sent 

  IP fast switching is enabled 

  IP fast switching on the same interface is disabled 

  IP Flow switching is enabled 

  IP Distributed switching is disabled 

  IP Flow switching turbo vector 

  IP Null turbo vector 

  IP multicast fast switching is enabled 

  IP multicast distributed fast switching is disabled 

  IP route-cache flags are Fast, Flow 

  Router Discovery is disabled 

  IP output packet accounting is disabled 

  IP access violation accounting is disabled 

  TCP/IP header compression is disabled 

  RTP/IP header compression is disabled 

  Probe proxy name replies are disabled 

  Policy routing is disabled 

  Network address translation is disabled 

  WCCP Redirect outbound is disabled 

  WCCP Redirect inbound is disabled 

  WCCP Redirect exclude is disabled 

  BGP Policy Mapping is disabled 

  IP multicast multilayer switching is disabled 

Configuring Distributed Switching

The following example shows how to enable distributed switching:

Router(config)# ip cef distributed 

Router(config)# interface ethernet 0/0/0 

Router(config-if)# ip route-cache distributed 

The following example shows that distributed Cisco Express Forwarding switching is for interface fastethernet 0/0/0:

Router# show cef interface fastEthernet 0/0/0 

FastEthernet0/0/0 is up (if_number 3) 

  Corresponding hwidb fast_if_number 3 

  Corresponding hwidb firstsw->if_number 3 

  Internet address is 10.1.1.254/24 

  ICMP redirects are always sent 

  Per packet load-sharing is disabled 

  IP unicast RPF check is disabled 

  Inbound access list is not set 

  Outbound access list is not set 

  IP policy routing is disabled 

  Hardware idb is FastEthernet0/0/0 

  Fast switching type 1, interface type 18 

  IP Distributed CEF switching enabled 

  IP Feature Fast switching turbo vector 

  IP Feature CEF switching turbo vector 

  Input fast flags 0x0, Output fast flags 0x0 

  ifindex 1(1) 

  Slot 0 Slot unit 0 VC -1 

  Transmit limit accumulator 0x48001A02 (0x48001A02) 

  IP MTU 1500 

Configuring Fast Switching for PBR

The following example shows how to configure a simple policy-based routing scheme and to enable FSPBR:

Router(config)# access-list 1 permit 10.1.1.0 0.0.0.255 

Router(config)# route-map mypbrtag permit 10 

Router(config-route-map)# match ip address 1 

Router(config-route-map)# set ip next-hop 10.1.1.195 

Router(config-route-map)# exit 

Router(config)# interface fastethernet 0/0/0 

Router(config-if)# ip route-cache policy 

Router(config-if)# ip policy route-map mypbrtag 

The following example shows that FSPBR is enabled for interface fastethernet 0/0/0:

Router# show ip interface fastEthernet 0/0/0 

FastEthernet0/0/0 is up, line protocol is up 

  Internet address is 10.1.1.254/24 

  Broadcast address is 255.255.255.255 

  Address determined by non-volatile memory 

  MTU is 1500 bytes 

  Helper address is not set 

  Directed broadcast forwarding is disabled 

  Multicast reserved groups joined: 224.0.0.10 

  Outgoing access list is not set 

  Inbound  access list is not set 

  Proxy ARP is enabled 

  Security level is default 

  Split horizon is enabled 

  ICMP redirects are always sent 

  ICMP unreachables are always sent 

  ICMP mask replies are never sent 

  IP fast switching is enabled 

  IP fast switching on the same interface is disabled 

  IP Flow switching is disabled 

  IP CEF switching is enabled 

  IP Distributed switching is enabled 

  IP Feature Fast switching turbo vector 

  IP Feature CEF switching turbo vector 

  IP multicast fast switching is enabled 

  IP multicast distributed fast switching is disabled 

  IP route-cache flags are Fast, Distributed, Policy, CEF 

  Router Discovery is disabled 

  IP output packet accounting is disabled 

  IP access violation accounting is disabled 

  TCP/IP header compression is disabled 

  RTP/IP header compression is disabled 

  Probe proxy name replies are disabled 

  Policy routing is enabled, using route map my_pbr_tag 

  Network address translation is disabled 

  WCCP Redirect outbound is disabled 

  WCCP Redirect inbound is disabled 

  WCCP Redirect exclude is disabled 

  BGP Policy Mapping is disabled 

  IP multicast multilayer switching is disabled 

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