13-5
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 13 Configuring CEF for PFC2 and PFC3A
Understanding How Layer 3 Switching Works
Understanding CEF for PFC2/PFC3A
Note
With Supervisor Engine 720 (MSFC3), IPX routing is done through the software.
These sections describe CEF for PFC2:
•
CEF for PFC2/PFC3A Overview, page 13-5
•
Understanding the Forwarding Decisions, page 13-6
•
Understanding the FIB, page 13-6
•
Understanding the Adjacency Table, page 13-7
•
Partially and Completely Switched Multicast Flows, page 13-9
•
CEF for PFC2/PFC3A Examples, page 13-10
CEF for PFC2/PFC3A Overview
Supervisor Engine 2, PFC2, and MSFC2 provide Layer 3 switching with CEF for PFC2. CEF for PFC2
is permanently enabled on Supervisor Engine 2. Cisco IOS CEF is permanently enabled on MSFC2 in
support of CEF for PFC2.
Supervisor Engine 720, PFC3A, and MSFC3 provide Layer 3 switching with CEF for PFC3A. CEF for
PFC3A is permanently enabled on Supervisor Engine 720. Cisco IOS CEF is permanently enabled on
MSFC3 in support of CEF for PFC3A.
CEF for PFC2/PFC3A works with CEF (for unicast traffic) and PIM (for multicast traffic) on
MSFC2/MSFC3 to support IP, IP multicast, and IPX traffic. CEF and PIM on MSFC2/MSFC3 are
enhanced to support CEF for PFC2/PFC3A. CEF for PFC2/PFC3A generates flow statistics for
Layer 3-switched traffic that can be displayed at the CLI or used for NDE.
CEF for PFC2/PFC3A provides Layer 3 switching for all packets that match a complete forwarding
information base (FIB) entry (see the
“Understanding the FIB” section on page 13-6
). CEF for
PFC2/PFC3A sends all packets that match an incomplete FIB entry (one where the MAC address has not
been resolved) to MSFC2/MSFC3 to be routed until MSFC2/MSFC3 resolves the MAC address.
Note
CEF for PFC2/PFC3A sends bridge traffic that is addressed at Layer 2 to MSFC2/MSFC3 to be
processed.
Note
Access control lists (ACLs) and policy-based routing can cause CEF for PFC2/PFC3A to ignore the FIB
when making a forwarding decision (see the
“Understanding the Forwarding Decisions” section on
page 13-6
).