7-18
Cisco SCE 8000 10GBE Software Configuration Guide
OL-30621-02
Chapter 7 Configuring Line Interfaces
Tunneling Protocols
From the SCE(config if)# prompt, type:
Configuring the L2TP Environment
•
External Fragmentation in the L2TP Environment, page 7-18
•
External Fragmentation in the L2TP Environment
If external fragmentation exists in the L2TP environment, it is required to configure a
quick-forwarding-ignore
traffic rule (see
“Configuring Traffic Rules and Counters” section on
) that bypasses all IP traffic targeted to either the LNS or LAC IP address. This will make sure
that any packets not having the L2TP port indication (i.e. non-first fragments) will not require handling
by the traffic processors.
In addition, to prevent reordering of L2TP tunneled fragments, it is advised to define a
quick-forwarding
traffic rule for all the L2TP traffic. This can be done based on the IP ranges in use by the internal IPs in
the tunnel (as allocated by the LNS), or simply for all the traffic passing through the Cisco SCE platform.
Note
By enabling quick forwarding, the Cisco SCE can only perform traffic monitoring for
externally-fragmented L2TP traffic. It cannot perform flow redirection, flow blocking, or rate limiting.
Options
The following option is available:
•
portnumber
—The port number that the LNS and LAC use for L2TP tunnels.
Default port# = 1701
From the SCE(config if)# prompt, type:
Asymmetric L2 Support
You should enable asymmetric layer 2 support in cases where the following conditions apply for any
flows:
•
Each direction of the flow has a different pair of MAC addresses.
•
The routers do not accept packets with the MAC address of the other link.
Command
Purpose
mpls {traffic-engineering skip|vpn skip}
Sets the MPLS environment.
Specify the desired MPLS mode.
Command
Purpose
L2TP identify-by port-number
portnumber
Configures the L2TP environment.
