Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual page 225

Chapter 13 Configuring CEF for PFC2
Access control lists (ACLs) and policy-based routing can cause CEF for PFC2 to ignore the FIB
Note
when making a forwarding decision (see the
page
Enter the show mls cef command to display a Layer 3 switching summary:
Console> (enable) show mls cef
Total L3 packets switched:
Total L3 octets switched:
Total route entries:
IP route entries:
IPX route entries:
IPM route entries:
IP load sharing entries:
IPX load sharing entries:
Forwarding entries:
Bridge entries:
Drop entries:
Understanding Forwarding Decisions
CEF for PFC2 provides Layer 3 switching based on:
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Enter the show mls entry command to display information about the entries used to make forwarding
decisions. CEF for PFC2 makes a forwarding decision for each packet and sends the rewrite information
for each packet to the egress port, where the rewrite occurs when the packet is transmitted from the
switch.
Understanding the FIB
The FIB resides in a separate TCAM. The adjacency table is stored separately in DRAM. The NetFlow
table is stored separately in DRAM. The FIB, the adjacency table, and the NetFlow table do not compete
with any other features for storage space.
The FIB is conceptually similar to a routing table. It maintains a mirror image of the forwarding
information contained in the unicast and multicast routing tables on the MSFC2. When routing or
topology changes occur in the network, the unicast and multicast routing tables on the MSFC2 are
updated and those changes are reflected in the FIB. The FIB maintains next-hop address information
based on the information in the routing tables on the MSFC2. The FIB supports 256K entries, which
includes 16K IP multicast entries. With reverse path forwarding (RPF) check enabled, the number of IP
entries doubles.
FIB lookup uses the following criteria:
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78-13315-02
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Entries in the ACL ternary content addressable memory (TCAM) for policy-based routing decisions
Entries in the NetFlow table for TCP intercept and reflexive ACL forwarding decisions (see the
"Understanding NetFlow Statistics" section on page
Entries in the FIB and adjacency table for all other forwarding decisions
Destination IP address for IP unicast
Destination IPX network for IPX unicast
Source and destination IP address for IP unicast with RPF check
Source and destination IP address for IP multicast with RPF check
"Understanding Forwarding Decisions" section on
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Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
Understanding How Layer 3 Switching Works
13-5