03-Layer 3-IP Services Configuration Guide

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06-Fast forwarding configuration
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06-Fast forwarding configuration 48.84 KB

Configuring fast forwarding

About fast forwarding

Fast forwarding reduces route lookup time and improves packet forwarding efficiency by using a high-speed cache and data-flow-based technology. It identifies a data flow by using the following fields: source IP address, source port number, destination IP address, destination port number, and protocol number. After a flow's first packet is forwarded through the routing table, fast forwarding creates an entry and uses the entry to forward subsequent packets of the flow.

Restrictions and guidelines: Fast forwarding configuration

Fast forwarding can process fragmented IP packets, but it does not fragment IP packets.

Configuring the aging time for fast forwarding entries

About this task

The fast forwarding table uses an aging timer for each forwarding entry. If an entry is not updated before the timer expires, the device deletes the entry. If an entry has a hit within the aging time, the aging timer restarts.


1.     Enter system view.


2.     Configure the aging time for fast forwarding entries.

ip fast-forwarding aging-time aging-time

By default, the aging time is 30 seconds.

Configuring fast forwarding load sharing

About this task

Fast forwarding load sharing enables the device to identify a data flow by using the five-tuple (source IP, source port, destination IP, destination port, and protocol).

If fast forwarding load sharing is disabled, the device identifies a data flow by the five-tuple and the input interface.


1.     Enter system view.


2.     Configure fast forwarding load sharing. Choose one option as needed:

¡     Enable fast forwarding load sharing.

ip fast-forwarding load-sharing

¡     Disable fast forwarding load sharing.

undo ip fast-forwarding load-sharing

By default, fast forwarding load sharing is enabled.

Display and maintenance commands for fast forwarding

Execute display commands in any view and reset commands in user view.




Display fast forwarding entries.

display ip fast-forwarding cache [ ip-address ] [ slot slot-number ]

Display fast forwarding entries about fragmented packets.

display ip fast-forwarding fragcache [ ip-address ] [ slot slot-number ]

Display the aging time of fast forwarding entries.

display ip fast-forwarding aging-time

Clear the fast forwarding table.

reset ip fast-forwarding cache [ slot slot-number ]


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