CEF-Based Multilayer Switching, deployingpptx

This ppt Explains the CEF-Based Multilayer Switching, deploying

Implementing Inter-VLAN Routing
Layer 3 Switch Processing
CEF-Based MLS Lookups
How to Troubleshoot CEF
Common CEF Problems

1. Implementing Inter- VLAN Routing E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Deploying CEF- Based Multilayer Switching

2. Layer 3 Switch Processing E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . In Layer 3 switches, the control path and data path are relatively independent. The control path code, such as routing protocols, runs on the route processor. Data packets are forwarded by the switching fabric.

3. Layer 3 Switch Processing (Cont.) E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Layer 3 switching can occur at two different locations on the switch. Centralized switching: Switching decisions are made on the route processor by a central forwarding table. Distributed switching: Switching decisions can be made on a port or line- card level. Layer 3 switching takes place using one of these two methods: Route caching: A Layer 3 route cache is built in hardware as the switch sees traffic flow into the switch. Topology- based switching: Information from the routing table is used to populate the route cache, regardless of traffic.

4. CEF- Based Multilayer Switches E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . CEF caches routing information in the FIB table and Layer 2 next- hop addresses in the adjacency table.

5. Multilayer Switch Packet Forwarding Process E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Some IP packets cannot be processed in hardware. If an IP packet cannot be processed in hardware, it is processed by the Layer 3 engine.

6. CEF- Based MLS Lookups Layer 3 packets initiate TCAM lookup. The longest match returns adjacency with rewrite information. The packet is rewritten per adjacency information and forwarded. E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 .

7. ARP Throttling E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 .

8. CEF- Based MLS Operation E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 .

9. Configuring and Verifying CEF E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Configuring CEF ip cef (enabled by default) ip route- cache cef (only on VLAN interface) Verifying CEF show ip cef fa 0/1 detail show adjacency fa 0/1 detail

10. Enabling CEF E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Switch(config- if)#ip cef Switch(config- if)#ip route- cache cef The commands required to enable CEF are platform dependent: On the Cisco Catalyst 4000 switch On the Cisco Catalyst 3550 switch

11. Verifying CEF E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Switch#show ip cef [type mod /port | vlan_interface ] [detail] Switch# show ip cef vlan 11 detail IP CEF with switching (Table Version 11), flags=0x0 10 routes, reresolve, unresolved (0 old, new), peak 13 leaves, 12 nodes, 14248 bytes, 14 inserts, 1 invalidations load sharing elements, bytes, references universal per- destination load sharing algorithm, id 4B936A24 2(0) CEF resets, revisions of existing leaves Resolution Timer: Exponential (currently 1s, peak 1s) in- place/0 aborted modifications refcounts: 1061 leaf, 1052 node Table epoch: (13 entries at this epoch) 172.16.11.0/24, version 6, epoch 0, attached, connected packets, bytes via Vlan11, dependencies valid glean adjacency

12. Common CEF Problems E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Is ideal switching method (CEF, DCEF) in use? Are CEF tables complete and accurate?

13. Verify Layer 3 Switching E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Switch#show interface {{type mod /port } | { port-channel number }} | begin L3 Switch# show interface fastethernet 3/3 | begin L3 L3 in Switched: ucast: pkt, bytes - mcast: 12 pkt, 778 bytes mcast L3 out Switched: ucast: pkt, bytes - mcast: pkt, bytes 4046399 packets input, 349370039 bytes, no buffer Received 3795255 broadcasts, 2 runts, giants, throttles ..... Switch#

14. Displaying Hardware Layer 3 Switching Statistics E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Switch#show interfaces {{ type mod/port } | {port-channel number }} include switched Switch# show interfaces gigabitethernet 9/5 | include switched L2 Switched: ucast: 8199 pkt, 1362060 bytes - mcast: 6980 pkt, 371952 bytes L3 in Switched: ucast: 3045 pkt, 742761 bytes - mcast: pkt, bytes mcast L3 out Switched: ucast: 2975 pkt, 693411 bytes - mcast: pkt, bytes

15. Adjacency Information Switch#show adjacency [{{ type mod/port } | {port- channel number }} | detail | internal | summary] Switch# show adjacency gigabitethernet 9/5 detail E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Protocol Interface Address IP GigabitEthernet9/5 172.20.53.206(11) 504 packets, 6110 bytes 00605C865B82 000164F83FA50800 ARP 03:49:31

16. Debugging CEF Operations E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Switch#debug ip cef {drops | access- list | receive | events | prefix- ipc | table} Displays debug information for CEF Switch#debug ip cef {ipc | interface- ipc} Displays debug information related to IPC in CEF Switch#ping ip Performs an extended ping

17. How to Troubleshoot CEF E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 .

18. Summary E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . Layer 3 switching is high- performance packet switching in hardware. MLS functionality can be implemented through CEF. CEF uses tables in hardware to forward packets. Specific commands are used to enable and verify CEF operations. Commands to enable CEF are platform dependent. CEF problems can be matched to specific solutions. Specific commands are used to troubleshoot and solve CEF problems. Ordered steps assist in troubleshooting CEF- based problems.

19. Module Summary E- TRAIN www.ciscotrain.com league.ciscotrain.com 010 82536886 010 82536887 . An external router can be configured to route packets between the VLANs on a Layer 2 switch. Multilayer switches allow routing and the configuration of interfaces to pass packets between VLANs. CEF- based multilayer switching facilitates packet switching in hardware.