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This feature module describes the Virtual Profile Cisco Express Forwarding feature. It includes information on the benefits of the new feature, supported platforms, supported standards, and the commands necessary to configure the Virtual Profile Cisco Express Forwarding feature.
This document includes the following sections:
The Virtual Profile Cisco Express Forwarding feature allows you to enable asynchronous and ISDN interfaces in Cisco Express Forwarding (CEF) switching. This feature allows you to create a datagram prefix and cache it in an adjacency table for fast reference and rewrite during the call setup.
FIB
Virtual Profile (VP) CEF switching allows the user to use the Forwarding Information Base (FIB) to look up a route for a forwarding packet. Because the FIB is populated by routing topology, not by traffic, the FIB is a performance enhancement over cache tables used in fast switching.
Integrate MPLS VPN/BGP
VP CEF switching enables VP to be used in other technologies that require CEF switching, such as MPLS Virtual Private Network/Border Gateway Protocol (VPN/BGP).
ISDN Interfaces
VP CEF allows you to enable ISDN interfaces in CEF switching.
When the Dialer Profile feature is configured for the physical interfaces, no virtual profile interface will be created.
For more information on configuring CEF, refer to the Cisco IOS Switching Services Configuration Guide.
For more information on the commands used to configure the Virtual Profile Cisco Express Forwarding feature, refer to the Cisco IOS Switching Services Command Reference.
Standards
None
MIBs
None
For descriptions of supported MIBs and how to use MIBs, see the Cisco MIB web site on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
RFC
None
See the following sections for configuration tasks for the Virtual Profile Cisco Express Forwarding feature. Each task in the list is identified as optional or required:
To enable CEF, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
ip cef |
To disable CEF operation, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
no ip cef | Disables CEF operation. |
When you enable CEF globally, all interfaces that support CEF are enabled by default. If you want to turn off CEF on a particular interface, you can do so.
You might want to disable CEF on a particular interface because that interface is configured with a feature that CEF does not support. For example, policy routing and CEF cannot be used together. You might want one interface to support policy routing while the other interfaces support CEF. In this case, you would enable CEF globally, but disable CEF on the interface configured for policy routing, enabling all but one interface to perform express forwarding.
To disable CEF on an interface, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
no ip route-cache cef | Disables CEF operation on the interface. |
When you disable CEF, Cisco IOS software switches packets using the next fastest switching path.
If you have disabled CEF operation on an interface and want to reenable it, you can do so by using the ip route-cache cef command in interface configuration mode.
CEF supports virtual profile switching. Virtual profile switching is enabled automatically when you enable CEF. You do not perform any additional tasks to enable virtual profile switching once you enable CEF.
To monitor and maintain virtual profile interfaces, use the following commands in privileged EXEC mode:
| Command | Purpose |
|---|---|
Router#show adjacency detail | Displays CEF adjacency table information. |
Router#show ip cef | Displays entries in the FIB that are unresolved or displays a summary of the FIB. |
Router#show ip interfaces virtual-access number | Displays network layer IP information about a specified virtual access interface. |
None
No new commands are introduced. All commands used with this feature are documented in the CiscoIOS Switching Services Command Reference.
Posted: Wed Jun 21 17:26:42 PDT 2000
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