1. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-1 Frame-Mode MPLS Implementation on Cisco IOS Platforms Introducing CEF Switching

2. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-2 Outline Overview What Are Cisco IOS Platform Switching Mechanisms? Using Standard IP Switching What Is the CEF Switching Architecture? Configuring IP CEF Monitoring IP CEF Summary

3. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-3 The Cisco IOS platform supports three IP switching mechanisms: Routing table driven switching—process switching –Full lookup for every packet Cache driven switching—fast switching –Most recent destinations entered in the cache –First packet always process-switched Topology driven switching –CEF (prebuilt FIB table) Cisco IOS Platform Switching Mechanisms

4. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-4 Standard IP Switching Review

5. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-5 CEF Switching Review

6. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-6 ip cef [distributed] Router(config)# Configuring IP CEF no ip route-cache cef Router(config-if)# Disables CEF switching on an interface Usually not needed This command starts CEF switching and creates the FIB table. The distributed keyword configures distributed CEF (running on VIP or line cards). All CEF-capable interfaces run CEF switching.

7. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-7 Monitoring IP CEF Router#show ip cef detail IP CEF with switching (Table Version 6), flags=0x0 6 routes, 0 reresolve, 0 unresolved (0 old, 0 new) 9 leaves, 11 nodes, 12556 bytes, 9 inserts, 0 invalidations 0 load sharing elements, 0 bytes, 0 references 2 CEF resets, 0 revisions of existing leaves refcounts: 543 leaf, 544 node Adjacency Table has 4 adjacencies 0.0.0.0/32, version 0, receive 192.168.3.1/32, version 3, cached adjacency to Serial0/0.10 0 packets, 0 bytes tag information set local tag: 28 fast tag rewrite with Se0/0.10, point2point, tags imposed: {28} via 192.168.3.10, Serial0/0.10, 0 dependencies next hop 192.168.3.10, Serial0/0.10 valid cached adjacency tag rewrite with Se0/0.10, point2point, tags imposed: {28} Router#show ip cef detail

8. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-8 Summary Three different switching mechanisms are used on Cisco IOS platforms: routing table driven, cache driven, and topology driven. Entries received with no destination address information are process-switched; subsequent packets are fast-switched. Generation of entries in the FIB table is caused by a change trigger; when something in the routing table changes, the change is also reflected in the FIB table. CEF is configured globally. The show ip cef command is used to monitor CEF operation.

9. © 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-9