Contents

Configuring fast forwarding· 1

About fast forwarding· 1

Restrictions and guidelines: Fast forwarding configuration· 1

Enabling/disabling fast forwarding· 1

Configuring the aging time for fast forwarding entries· 2

Configuring fast forwarding load sharing· 2

Verifying and maintaining fast forwarding· 2

Displaying the aging time of fast forwarding entries· 2

Displaying and clearing fast forwarding entries· 2

Displaying fast forwarding entries about fragmented packets· 3

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.

Enabling/disabling fast forwarding

About this task

The fast forwarding feature will create fast forwarding entries for the device to speed up forwarding. A large number of fast forwarding entries will cause high memory usage, which eventually leads to memory allocation failure for other services. In this case, you can disable fast forwarding temporarily to free up the device memory.

Restrictions and guidelines

Do not disable fast forwarding if the device runs session-based services. Disabling fast forwarding will make these services become ineffective:

·     NAT.

·     ASPF.

·     Attack detection and prevention.

Procedure

1.     Enter system view.

system-view

2.     Configure fast forwarding.

¡     Enable fast forwarding.

ip fast-forwarding enable

¡     Disable fast forwarding.

ip fast-forwarding enable

By default, fast forwarding is enabled.

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.

Procedure

1.     Enter system view.

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 packet information.

If fast forwarding load sharing is disabled, the device identifies a data flow by the packet information and the input interface.

Procedure

1.     Enter system view.

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.

Verifying and maintaining fast forwarding

Displaying the aging time of fast forwarding entries

To display the aging time of fast forwarding entries, execute the following command in any view:

display ip fast-forwarding aging-time

Displaying and clearing fast forwarding entries

To display fast forwarding entries, execute the following command in any view:

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

To clear fast forwarding entries, execute the following command in user view:

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

Displaying fast forwarding entries about fragmented packets

To display fast forwarding entries about fragmented packets, execute the following command in any view:

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