注意:要防止高頻寬的介面寫到低頻寬界面的阻塞, 建議no ip route-cache
ip route-cache
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 CEF or dCEF on the physical interface as well as all subinterfaces associated with the physical interface
show ip cache flow
使用clear ip flow stats可將上述狀態清除
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
Enables (ingress) NetFlow accounting for traffic arriving on an interface.
ip route-cache distributed
The distributed option is supported on Cisco routers with line cards and Versatile Interface Processors (VIPs) that support both CEF and flow 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
ip route-cache cef
In some instances, you might want to disable CEF or dCEF on a particular interface because that interface is configured with a feature that CEF or dCEF does not support. Because all interfaces that support CEF or dCEF are enabled by default when you enable CEF operation globally, you must use the no form of the ip route-cache cef command in the interface configuration mode to turn CEF operation off a particular interface. To reenable CEF or dCEF operation, use the ip route-cache cef command.
Disabling CEF or dCEF on an interface disables CEF switching for packets forwarded to the interface, but has no effect on packets forwarded out of the interface.
Additionally when you disable CEF or dCEF, Cisco IOS software switches packets using the next-fastest switching path. In the case of dCEF, the next-fastest switching path is CEF on the RSP.
Note 
On the Cisco 12000 Series Internet Router, you must not disable dCEF on an interface
On the Cisco 12000 Series Internet Router, you must not disable dCEF on an interface
ip route-cache policy
1. If Cisco Express Forwarding (CEF) is already enabled, this command is not needed because PBR packets are CEF switched by default.
If Cisco Express Forwarding (CEF) is already enabled, this command is not needed because PBR packets are CEF switched by default.
2. Before you can enable fast-switched PBR, PBR itself must be configured.
Before you can enable fast-switched PBR, PBR itself must be configured.
3. FSPBR supports all of PBR's match commands and most of PBR's set commands, with the following restrictions:
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 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.
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.
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