Los Medanos College

1. Los Medanos College Introduction to Cisco Network Devices Mark McGregor, Instructor April, 2005

2. Module 2: Configuring Catalyst Switches

3. Basic Layer 2 Switching and Bridging Functions

4. The Stonge Age of LANs thicknet repeater Doesn’t scale. As you add nodes, you increase chance of collisions and reduce effective bandwidth. 10Base5 802.3 Ethernet: Coax bus. Shared Media. CMSA/CD 10Mbps shared. Actual speeds per host may hover around 1 Mbps or even less.

5. BRIDGE Segment Alpha Segment Bravo The Dark Ages of LANs UTP Hub Hub Scales by “segmenting” network. As you add nodes to each segment, you increase chance of collisions and reduce effective bandwidth on that segment. 10BaseT 802.3 Ethernet: UTP star. Shared Media. CMSA/CD Still 10Mbps shared. Broadcast problem – one broadcast domain.

6. Network Alpha Network Bravo The Dark Ages of LANs UTP Hub Hub L3 Router Scales by “subnetting” network. Early L3 routers added significant latency. If hosts on Alpha need to send tons of data to the server on Bravo…bottleneck. 10BaseT 802.3 Ethernet: UTP star. Shared Media. CMSA/CD Still 10Mbps shared. But broadcasts are controlled – at the expense of added latency

7. Today: Micro-Segmentation Scales by “microsegmenting” the network. Each host is on its own segment. No collisions if operating in full-duplex mode. 10/100/1000BaseT 802.3 Ethernet: UTP star. Not shared. 10/100/1000 dedicated. But broadcasts are still a problem!

8. Broadcast Issues In a flat Layer 2 network, broadcast frames, such as ARP, or Windows NetBIOS (over IP), are sent everywhere. The probability of broadcast storms increases as the network and number of users grows.

9. L3 Broadcast Filtering Layer 3 routers are used to create more manageable broadcast domains. Broadcasts do not pass through routers. This scenario can create a bottleneck in the network.

10. VLAN Trunks Multilayer Switch (L3-capable switch) VLAN Broadcast Filtering VLANs also can be used to create more manageable broadcast domains. Traffic from one VLAN cannot cross into another VLAN unless it is routed at Layer 3.

11. Today’s LANs • Hosts are mostly switched, few are shared (using hubs) • Fast Layer-3 (L3) routers are used to provide scalability • L3 routing often built-in to backplane of switch • Groups of users are determined by physical location • We are seeing a trend away from end-to-end user grouping (end-to-end VLANs)

12. Local Service Remote Service Enterprise Services Today’s Campus LANs From Host A’s point of view…. A Campus Backbone

13. Switch Operation

14. How Switches Work • A switch can create a network that behaves like it only has two nodes - the sender and the receiver. • These two nodes share the 10 Mbps bandwidth between them, available bandwidth can reach closer to 100%.

15. How Switches Work • Switches are high speed multi-port bridges with one port for each node or segment of the LAN. • A switch segments a LAN into microsegments creating collision free domains from one larger collision domain.

16. Microsegmentation

17. Switch Latency • Switches add latency, but they can overcome this by forwarding frames before they are completely received.

18. Two Switching Methods

19. Cut-through v. Store & Forward

20. Full-Duplex Ethernet • Allows the transmission of a packet and the reception of a different packet at the same time. • Requires two pairs of wires and a switched connection between each node. • Point-to-point connection, nearly collision free. • No negotiations for bandwidth.

21. Full-Duplex Ethernet • Offers 100% bandwidth in both directions (potential 20 Mbps, 200 Mbps, etc).

22. Switches and Broadcasts

23. Switches Learn the Network

24. CAM • Content Addressable Memory • An Ethernet switch can learn the address of each device on the network by • reading the source address of each packet transmitted and • noting the port where the frame was heard • Addresses are learned dynamically. • as new addresses are read they are learned and stored in content addressable memory (CAM). • when a source is read that is not found in the CAM it is learned/stored for future use.

25. Aging Out • Each time an address is stored it is time stamped. • allows for addresses to be stored for a set period of time • Each time an address is referenced or found in the CAM, it receives a new time stamp • Addresses that are not referenced during set period of time are removed from the list • By removing old addresses the CAM maintains an accurate and functional forwarding database

26. Key Characteristics of Various Switching Technologies

27. Switching • Layer 2 Switching • Switches based on MAC address • Layer 3 Switching • Switching at L2, hardware-based routing at L3 • Layer 4 Switching • Switching at L2, hardware-based routing at L3, with decisions optionally made on L4 information (port numbers)

28. Layer 2 Switching

29. Layer 3 Switching

30. Layer 4 Switching

31. MLS (Multi-Layer Switching)

32. MLS • Cisco’ specialized form of switching and routing, not generic L3 routing/L2 switching • cannot be performed using LMC lab equipment

33. MLS • sometimes referred to as “route once, switch many”

34. Cisco Catalyst Switches

35. Switch Block - AL • Catalyst 2950 Switch: • Supports minimal L3 routing • Up to 50 ports

36. Switch Block - AL • Catalyst 3550/3560 Switch: • Supports L3 routing • Up to 50 ports

37. Switch Block - AL • Catalyst 3750 Switch: • Supports L3 routing • Suports Cisco StackWise technology • Provides 32-Gbps high-speed stacking bus

38. Switch Block - DL • Catalyst 4000 Switch: • Supports L3 blades, high density access ports • 4006 (6 slots) shown here

39. Switch Block - DL • Catalyst 4500 Switch: • Supports L3 blades, high density access ports • Up to 10 slots

40. Switch Block - DL • Catalyst 6500 Switch: • Supports L3 blades, high density access ports • Can have up to 13 slots

41. Spanning Tree

42. Spanning-Tree Protocol • allows redundant switched/bridged paths without suffering the effects of loops in the network.

43. STP States

44. IOS Switch Configuration

45. Catalyst Switches • Catalyst Switching product line began as a Frankenstein of numerous acquisitions, including: • Crescendo (1993) • Kalpana (1994) • Grand Junction (1995) • Result – the operating systems of Catalyst products did not look the same, nor did they initially align with Cisco IOS

46. Catalyst Switches • Catalyst derived from the Crescendo acquisition (Cat 5000) ran an OS known as CatOS. • Sometimes referred to as “set-based” OS because (unlike the IOS) many configurations required the use of the set command. • The 5000 evolved into other big Cats (5500, 6000, and 6500) which also initially ran CatOS.

47. Catalyst Switches • Smaller, “work-group” access switches ran various specialized Operating Systems • Most were menu-driven • 1700, 1900, etc. • As this “work-group” Catalyst evolved, they dropped menus in favor of an IOS-like operating system.

48. Catalyst Switches • Today, all current Cisco Catalyst products have converged to use the Cisco IOS. • You are very likely to see legacy CatOS out in the real world – so you should be aware of it. • Cisco has stopped testing on CatOS for its CCNA, CCNP and CCIE R&S exams.

49. Configuring Cat Switches • Because Catalyst switches run IOS, you can apply the same configuration principles you’ve learned for configuring routers to configuring switches.

50. Configuring IOS-based Catalyst Switches