1. 1 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Is It Routing or Is It Layer 3 Switching? YES! Learn It and Use It Pete AndersonSteve Stiles Assistant Professor Instructor Davenport UniversityJames A Rhodes State College

2. 2 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Introductions – 5 minutes What is Layer 3 Switching?– 5 minutes How does it relate to Network Design? – 5 minutes Comparison Routers/L3 Switches – 5 minutes Technologies – 35 minutes Hands-On Labs - 35 minutes

3. Introductions

4. What is Layer 3 Switching?

5. 5 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Layer 3 switching speeds approximate that of Layer 2 switches Hardware-based routing using Application-Specific Integrated Circuits (ASICs) Make use of TCAM (Ternary Content Addressable Memory) for routing, ACL lookups, policy etc. Make use of CEF (Cisco Express Forwarding) RIP, OSPF, and EIGRP are supported Future: Pure Layer 3 environment leveraging inexpensive L3 access layer switches Layer 4 switching enables load balancing based on Layer 4 port number Layer 7 switching uses Network-Based Application Recognition (NBAR) to permit or deny traffic based on data passed by an application

6. 6 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada  CEF uses special strategies to switch data packets to their destinations expediently. It caches the information generated by the Layer 3 routing engine even before the switch encounters any data flows.  CEF caches routing information in one table (FIB) and caches Layer 2 next-hop addresses and frame header rewrite information for all FIB entries in another table, called the adjacency table (AT).

7. How does it relate to Network Design?

8. 8 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Layer 3 switches usually have packet-switching throughputs in the millions of packets per second (pps) Traditional general-purpose routers provide packet switching in the range of 100,000 pps to over 1 million pps

9. 9 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Aggregates distribution layer switches. Implements scalable protocols and technologies and load balancing. High-speed layer 3 switching using 10-Gigabit Ethernet. Uses redundant L3 links. For small networks, a core layer is not needed. In this case, the distribution layer switches need to be fully meshed. Recommended practice is to deploy a dedicated core layer to connect 3 or more physical segments or 4 or more pairs of building distribution switches.

10. 10 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada High availability, fast path recovery, load balancing, QoS, and security Route summarization and packet manipulation Redistribution point between routing domains Packet filtering and policy routing to implement policy-based connectivity Terminate VLANs First Hop Redundancy Protocol

11. 11 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Convergence – provides inline Power over Ethernet (PoE) to support IP telephony and wireless access points. Security – includes port security, DHCP snooping, Dynamic ARP inspection, IP source guard.

12. Comparison Routers/L3 Switches

13. 13 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Both routers and multilayer switches use routing protocols or static routes to maintain information about reachability and direction to network destinations (prefixes) and record this information in a routing table. Routers connect heterogeneous networks and support a wide variety of media and interfaces. Multilayer switches typically connect homogenous networks. Nowadays LAN switches are mostly Ethernet only. SimilaritiesDifferences

14. 14 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Perform the same functional packet switching actions: 1. Receive a frame and strip off the Layer 2 header. 2. Perform a Layer 3 lookup to determine the outbound interface and next hop. 3. Encapsulate the packet in a new Layer 2 frame and transmit the frame. Multilayer switches use specialized hardware to achieve wire-speed Ethernet-to-Ethernet packet switching. Low- to mid-range routers use multipurpose hardware to perform the packet-switching process. On average, the packet- switching throughput of routers is lower than the packet-switching throughput of multilayer switches. SimilaritiesDifferences

15. 15 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Routers usually support a wider range of features, mainly because switches need specialized hardware to be able to support certain data plane features or protocols. On routers, you can often add features through a software update. SimilaritiesDifferences

16. Technologies

17. 17 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada A Logical Demonstration of a Multilayer Switch:

18. SVIs Switched Virtual Interfaces

19. 19 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Configured on multilayer switches, one per VLAN. The management interface on an L2 switch is an SVI, but an L2 switch is limited to one active SVI. An SVI associates with an L2 VLAN – a switch must have an active L2 instance of a VLAN in order for an (L3) SVI to function.

20. 20 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Switch(config)# ip routing Switch(config)# router rip Switch(config-router)# network 10.0.0.0 Switch(config)# interface vlan 10 Switch(config-if)# ip address 10.10.1.1 255.0.0.0 Switch(config-if)# no shutdown Switch(config-if)# interface vlan 20 Switch(config-if)# ip address 10.20.1.1 255.255.255.0 Switch(config-if)# no shutdown

21. Layer 2 Etherchannels

22. 22 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Up to 8 physical links can be bundled into a single logical EtherChannel link. Usually EtherChannel is used for trunk links. Configuration applied to port channel interface affects all physical interfaces assigned to the port channel. Load balancing takes place between the physical links in an EtherChannel.

23. 23 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Port Aggregation Protocol (PAgP) is a Cisco-proprietary protocol that aids in the automatic creation of Fast EtherChannel links. Link Aggregation Control Protocol (LACP) is part of an IEEE specification (802.3ad) that also enables several physical ports to be bundled together to form an EtherChannel.

24. 24 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada ModePurpose AutoPlaces an interface in a passive negotiating state in which the interface responds to the PAgP packets that it receives but does not initiate PAgP negotiation (default). DesirablePlaces an interface in an active negotiating state in which the interface initiates negotiations with other interfaces by sending PAgP packets. Interfaces configured in the “on” mode do not exchange PAgP packets. OnForces the interface to channel without PAgP. Non-silentIf a switch is connected to a partner that is PAgP-capable, configure the switch interface for non-silent operation. The non-silent keyword is always used with the auto or desirable mode. If you do not specify non-silent with the auto or desirable mode, silent is assumed. The silent setting is for connections to file servers or packet analyzers; this setting enables PAgP to operate, to attach the interface to a channel group, and to use the interface for transmission.

25. 25 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada ModePurpose PassivePlaces a port in a passive negotiating state. In this state, the port responds to the LACP packets that it receives but does not initiate LACP packet negotiation (default). ActivePlaces a port in an active negotiating state. In this state, the port initiates negotiations with other ports by sending LACP packets. OnForces the interface to the channel without PAgP or LACP.

26. 26 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Switch(config)# interface fastethernet 0/23 Switch(config-if)# channel-group 2 mode active Switch(config)# interface fastethernet 0/24 Switch(config-if)# channel-group 2 mode active Switch(config)# interface port-channel 2 Switch(config-if)# switchport mode trunk Switch(config-if)# switchport trunk native VLAN 99 Switch(config-if)# switchport trunk allowed VLAN 2,3,99 Remote Switch configuration RSwitch(config)# interface fastethernet 0/23 RSwitch(config-if)# channel-group 5 mode on RSwitch(config)# interface fastethernet 0/24 RSwitch(config-if)# channel-group 5 mode on RSwitch(config)# interface port-channel 5 RSwitch(config-if)# switchport mode trunk RSwitch(config-if)# switchport trunk native VLAN 99

27. 27 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada When several port-channel interfaces are configured on the same device, the show etherchannel summary command is useful for displaying one-line information per port-channel. Layer 2 EtherChannels are all in use (SU next to the port-channel number). Switch# show etherchannel summary Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use f - failed to allocate aggregator M - not in use, minimum links not met u - unsuitable for bundling w - waiting to be aggregated d - default port Number of channel-groups in use: 2 Number of aggregators: 2 Group Port-channel Protocol Ports ------+-------------+-----------+-------------------------------------------- 2 Po2(SU) LACP g0/49(P) g0/50(P) g0/51(P) g0/52(P) 7Po7(SU) LACP g0/47(P) g0/48(P) 9 Po9(SU) PAgP g0/8(P) g0/9(P)

28. Routed Ports

29. 29 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Use the no switchport command to configure a physical switch port as a routed port. (3560) Routed ports are used in conjunction with SVI’s. Routed ports connect point- to-point (L3) links between distribution layer and core layer switches. A 48-port L3 switch can be configured as a 48-port router.

30. 30 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Switch(config)# interface GigabitEthernet 1/1 Switch(config-if)# no switchport Switch(config-if)# ip address 10.10.1.1 255.255.255.252 Switch(config-if)# exit ** Switch will let us know when we get forgetful ** Switch(config)# interface GigabitEthernet 1/2 Switch(config-if)# ip address 10.20.1.254 255.255.255.252 % IP addresses may not be configured on L2 links. Switch(config-if)# no switchport Switch(config-if)# ip address 10.20.1.254 255.255.255.252

31. Layer 3 Etherchannels

32. 32 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada Just as with physical interfaces on multilayer switches, bundles of interfaces (port channels) can be configured as routed ports. Port channels configured as routed ports are called L3 EtherChannels. L2 EtherChannels are normally used only when connecting from an access layer switch.

33. 33 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada

34. 34 © 2012 Cisco Systems, Inc. All rights reserved. Cisco confidential.Cisco Networking Academy, US/Canada