Configuring fast forwarding· 1

Overview·· 1

Configuration procedure· 1

Displaying and maintaining fast forwarding· 1

Fast forwarding configuration example· 2

Network requirements 2

Configuration procedure· 2

Verifying the configuration· 3

 

The device operates in IRF or standalone (the default) mode. For information about IRF mode, see IRF Configuration Guide.

Overview

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

Some features, such as packet queue management and header compression, can reduce fast forwarding performance.

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

Configuration procedure

To configure fast forwarding:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable fast forwarding.	ip fast-forwarding	By default, fast forwarding is enabled.
3.     Configure the aging time of fast forwarding entries.	ip fast-forwarding aging-time aging-time	By default, the aging time is 30 seconds.

 

Displaying and maintaining fast forwarding     

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

 

Task	Command
Display fast forwarding table information (in standalone mode).	display ip fast-forwarding cache [ ip-address ] [ slot slot-number ]
Display fast forwarding table information (in IRF mode).	display ip fast-forwarding cache [ ip-address ] [ chassis chassis-number slot slot-number ]
Display fast forwarding table information about fragmented packets (in standalone mode).	display ip fast-forwarding fragcache [ ip-address ] [ slot slot-number ]
Display fast forwarding table information for fragmented packets (in IRF mode).	display ip fast-forwarding fragcache [ ip-address ] [ chassis chassis-number slot slot-number ]
Display the aging time of fast forwarding entries.	display ip fast-forwarding aging-time
Clear fast forwarding table information (in standalone mode).	reset ip fast-forwarding cache [ slot slot-number ]
Clear fast forwarding table information (in IRF mode).	reset ip fast-forwarding cache [ chassis chassis-number slot slot-number ]

 

Fast forwarding configuration example

By default, Ethernet, VLAN, and aggregate interfaces are down. To configure such an interface, bring the interface up by executing the undo shutdown command.

Network requirements

Enable fast forwarding on Switch B.

Figure 1 Network diagram

 

Configuration procedure

1.      Configure Switch A:

# Configure the IP address of VLAN-interface 100.

<SwitchA> system-view

[SwitchA] interface vlan-interface 100

[SwitchA-Vlan-interface100] ip address 11.1.1.1 255.0.0.0

[SwitchA-Vlan-interface100] quit

# Configure a static route.

[SwitchA] ip route-static 22.1.1.0 255.0.0.0 11.1.1.2

2.      Configure Switch C:

# Configure the IP address of VLAN-interface 101.

<SwitchC> system-view

[SwitchC] interface Vlan-interface101

[SwitchC-Vlan-interface101] ip address 22.1.1.2 255.0.0.0

[SwitchC-Vlan-interface101] quit

# Configure a static route.

[SwitchC] ip route-static 11.1.1.0 255.0.0.0 22.1.1.1

3.      Configure Switch B:

# Enable fast forwarding.

<SwitchB> system-view

[SwitchB] ip fast-forwarding

# Configure the IP addresses of VLAN-interface 100.

[SwitchB] interface Vlan-interface100

[SwitchB-Vlan-interface100] ip address 11.1.1.2 255.0.0.0

[SwitchB-Vlan-interface100] quit

# Configure the IP address of VLAN-interface 101.

[SwitchB] interface Vlan-interface101

[SwitchB- Vlan-interface101] ip address 22.1.1.1 255.0.0.0

[SwitchB- Vlan-interface101] quit

Verifying the configuration

# Display the fast forwarding table on Switch B.

[SwitchB] display ip fast-forwarding cache

The output shows that no fast forwarding entry exists.

# Ping the IP address of Ethernet 1/2 of Switch C from Switch A. Reply packets can be received.

[SwitchA] ping 22.1.1.2

  PING 22.1.1.2: 56  data bytes, press CTRL_C to break

    Reply from 22.1.1.2: bytes=56 Sequence=1 ttl=254 time=2 ms

    Reply from 22.1.1.2: bytes=56 Sequence=2 ttl=254 time=1 ms

    Reply from 22.1.1.2: bytes=56 Sequence=3 ttl=254 time=1 ms

    Reply from 22.1.1.2: bytes=56 Sequence=4 ttl=254 time=2 ms

    Reply from 22.1.1.2: bytes=56 Sequence=5 ttl=254 time=2 ms

 

  --- 22.1.1.2 ping statistics ---

    5 packet(s) transmitted

    5 packet(s) received

    0.00% packet loss

    round-trip min/avg/max = 2/2/3 ms

# Display the fast forwarding table on Switch B.

[SwitchB] display ip fast-forwarding cache

Total number of fast-forwarding entries: 2

SIP         SPort DIP        DPort Pro   Input_If            Output_If           Flg

22.1.1.2    0     11.1.1.1   0     1     Vlan-interface101   Vlan-interface100   7

11.1.1.1    8     22.1.1.2   0     1     Vlan-interface100   Vlan-interface101   7

The output shows that fast forwarding entries have been created.