|
|
This feature module describes the Distributed GRE Tunneling Support feature. It includes information on the benefits of the new feature, supported platforms, supported standards, and the commands necessary to configure the Distributed GRE Tunneling Support feature.
This document includes the following sections:
The Distributed GRE Tunneling Support feature allows Cisco IOS software to switch packets into and out of the generic routing encapsulation (GRE) tunnels using distributed Cisco Express Fowarding (dCEF). The tunneling is performed using recursive or "double" switching techniques that are currently deployed on existing nondistributed platforms. The relevant bits are ported into this development.
Double switching is performed by the handling of the received IP packet in the existing code path until it is determined that the packet needs encapsulation or de-encapsulation. Recursively forwarding the IP packet through the IP switching path again explains the "double" aspect of the switching.
The GRE tunneling allows service providers to support a large number of tunnels by forwarding distributed tunneled packets. This feature is an extension of the nondistributed forwarding information base (FIB) forwarding paths.
For more information on dCEF, refer to the "Configuring Cisco Express Forwarding" chapter in the Cisco IOS Switching Services Configuration Guide.
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.
RFCs
dCEF must be explicitly enabled on the router.
None
None
None
CEF ---A mode of packet switching in Cisco IOS Software. Also known as FIB-switching.
Gen Generator---Router used to generate test packets.
Ref Reflector---Router used to receive test packets and send replies.
UUT---Unit Under Test---Router running the image to be tested.
Posted: Mon Jun 19 13:25:58 PDT 2000
Copyright 1989 - 2000©Cisco Systems Inc.