Ethernet Basics Learning Switches. based on Chapter 4 of CompTIA Network+ Exam Guide, 4 th ed., Mike Meyers

Transcription

1 Ethernet Basics Learning Sitches based on Chapter 4 of CompTIA Netork+ Eam Guide, 4 th ed., Mike Meers

2 Sitch Forarding A sitch forards frames based on destination MAC address Ho does the sitch kno hich port a given MAC address is on?

3 Learning sitches Incoming frames ith unrecognied destinations are flooded to all ports - The frame's source MAC address is associated ith the incoming sitch port» This is the learning part Incoming frames destined for recognied MAC addresses are forarded onl to the associated port Flash animation: - montcs.bloomu.edu/netorking/simulations/sitchsi mulation.sf

4 Learning Sitches - initial 0 A B 2 5 Initiall, sitches A and B do not kno ho is attached here.

5 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port /1/data 2 A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

6 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port /1/data A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

7 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port /1/data 5/1/data A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 5/1/data 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

8 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5/1/data 5 3 5/1/data 5/1/data 4

9 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 0/5/data 4

10 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 0/5/data 5 3 4

11 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port A 0/5/data 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 0/5/data 4 0/5/data

12 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port. 0 0/5/data 1 2 0/5/data 0/5/data A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

13 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port. 0 5/1/data 1 2 A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

14 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port /1/data A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

15 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5/1/data 5 3 4

16 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 5/1/data 4

17 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port. 0 1/0/data 1 2 A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

18 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port /0/data A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

19 Learning Sitches eample 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port /0/data 2 A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

20 Learning Sitches eample all steps 1. Node 1 builds frame to send to node Node 1 transmits frame to sitch A. 3. Sitch A floods frame to node 0, node 2, and sitch B. a. Sitch A associates MAC address 1 ith its port. 4. Sitch B floods frame to node 3, node 4, and node 5. a. Sitch B associates MAC address 1 ith its port. 5. Node 5 builds frame to send to node Node 5 transmits frame to sitch B. 7. Sitch B floods frame to node 3, node 4, and sitch A. a. Sitch B associates MAC address 5 ith its port. 8. Sitch A floods frame to node 0, node 1, and node 2. a. Sitch A associates MAC address 5 ith its port A 9. Node 1 builds another frame to send to node Node 1 transmits frame to sitch A. 11. Sitch A forards frame to its port. 12. Sitch B forards frame to its port. 13. Node 0 builds frame to send to node Node 0 transmits frame to sitch A. 15. Sitch A forards frame to its port. a. Sitch A associates MAC address 0 ith its port. B 5 3 4

21 Learning Sitches Summar Frames destined for unrecognied destinations are flooded to all ports Frames hose destinations are knon get forarded onl to the proper port - Broadcast frames alas flooded Frame source MACs are learned as the frames arrive at the sitch Dnamic process nel-connected nodes are learned henever the begin transmitting

22 Bridge Loops, Broadcast Storms, and the Spanning Tree Algorithm Dealing ith redundant pathas through the LAN

23 A Reason For Multiple Paths In this netork, the backbone and distribution sitches are doubled, for redundanc. One path should be preferred, until it becomes unavailable. Then another path should take over.

24 Topologies revisited "Core-Distribution- Access" topolog in enterprise netorks - "Fat-tree" model Higher-level links have higher bandidths "Leaf-Spine" topolog in data centers provides multiple paths beteen leaf nodes - Multiple paths can/should be used, for better performance

25 The Problem: Bridge Loops What is the proper path from PC1 to the Web Server? When started, sitches forard frames to all ports. Broadcast frames must be forarded to all other ports. This can result in frames looping endlessl beteen sitches.

26 Bridge Loops and Broadcast Storms PC1 sends an "ho-has" frame, to find the Web Server queries must be broadcast, so sitches ill flood them out

27 Broadcast Storm: 1 Access sitch floods the frame out to both Distribution sitches

28 Broadcast Storm: 2a Each Distribution sitch floods out the received frame - to both Backbone sitches - back to the other Access sitch

29 Broadcast Storm: 2b Backbone sitches and Access sitch each receive to copies of the frame - don't kno the're the same frame Each sitch must flood out both copies

30 Broadcast Storm: 3a Backbone sitches echange copies of the frames, hile flooding them to the Distribution sitches Other Access sitch floods frames back - Distribution sitches - (other

31 Broadcast Storm: 3b Backbone sitches have to ne copies to flood out Distribution sitches receive three or four copies, ill flood out each cop PC2 gets to copies - ignores them

32 Broadcast Storm: ad infinitum Backbone sitches keep echoing frames beteen themselves, hile receiving more copies from the Distribution sitches Distribution, Access sitches do the same

33 Broadcast Storm: result Within seconds, the netork is overhelmed ith copies of the frame No other traffic can get through Turn it all off, and start over

34 One Solution: the Spanning Tree Algorithm Algorithm b Radia Perlman Select a root sitch Determine shortest paths via the root Block (don t forard onto) ports that aren t on the shortest path Onl one path beteen leaf nodes is in use at an one time - some phsical capacit is under-used

35 Spanning Tree standards Spanning Tree Protocol (STP) , developed b Digital Equipment Corp. IEEE 802.1D part of Logical Link Control sublaer - not compatible ith DEC's STP - IEEE Rapid Spanning Tree Protocol» Faster identification of shortest paths - IEEE 802.1s Multiple Spanning Tree Protocol» used ith Virtual LANs (VLANs)

36 802.1D high points Bridges (sitches) echange Bridge Protocol Data Unit (BPDU) frames - repeated ever to seconds These contain Bridge IDs - similar to MAC address - also includes a priorit value» often a constant, and equal, default value Loest bridge ID becomes root bridge Other bridges identif shortest paths to/from the root bridge

37 Sitches and STP States 1. Blocking state - Startup state for all ports - process BPDUs to determine root port, designated ports - Also applied to ports that aren't on a shortest-path-to-root 2. Listening state - process BPDUs, verif no bridge loops; no forarding 3. Learning state - process user frames (but don't forard), update MAC address table 4. Forarding state - process user frames and forard them based on MAC address table Disable state - Sitch ports turned off b administrator

38 Spanning Tree Simulation, from Cisco Sstems This Flash animation shos three sitches negotiating the proper paths. - Web Link: montcs.bloomu.edu/netorking/simulations/ Cisco/spanning_tree1.sf

39 TRILL and SPB protocols alternatives to STP Adapt laer-3 routing algorithms to laer-2 connections Multiple pathas used simultaneousl, but no bridge loops - improved link utiliation, better performance TRILL "Transparent Interconnection of Lots of Links" - RFC 6325, developed b Radia Perlman SPB "Shortest Path Bridging" - IEEE-802.1aq, adopted March 2012

40 Cisco's vie of SPB SPBV SPB for VLANs SPBM SPB for MACs

41 Avaa Netorks SPBm and SPB headers

42 Bridge Loops Summar Redundant links beteen sitches - Fault tolerance - Can cause bridge loops Spanning Tree algorithms - STP, 802.1D turn off some sitch ports to interrupt bridge loops - RSTP finds shortest paths more quickl - MSTP VLAN support TRILL, SPB protocols - Allo use of all links for high performance

43 Finding Neighbors on the LAN three supporting protocols at Laer 2

44 Finding LAN neighbors Netork nodes can discover neighbors b broadcasting frames and listening for replies Open, proprietar protocols - LLDP specified b IEEE 802.1ab» Link-Laer Discover Protocol - CDP Cisco sitches and routers» Cisco Discover Protocol - LLTD Microsoft Windos 7 / Vista / 8 / 10» Link-Laer Topolog Discover

45 Neighbor discover protocols Laer-2 "applications" information carried directl in Ethernet frames - No IP addresses or laer-3 protocols involved

46 Running a discover protocol CDP is enabled b default on Cisco equipment - proprietar - intended for routers and sitches LLTD is Microsoft-proprietar - source code for Linu client released, but then removed again LLDP can be enabled on Cisco gear, is available on Windos 8 and 10, and can be installed on Linu and Windos 7

47 CDP Cisco sitches and routers Small netork simulated in GNS3 CDP report for router R1 - shos hat is connected, to hich port

48 LLTD Windos 7 displa of LAN The Win7 node discovered a WinXP neighbor and a Win10 neighbor The sitch/hub/gatea topolog is all virtual

49 LLDP neighbor discover from Linu

50 Neighbor Discover Protocols Summar LLTD - Proprietar, Microsoft-oriented; comple protocol - Focused on client sstems - Broadcasts frames hen map is requested CDP - Proprietar, Cisco-onl - Identifies netorking nodes (sitches, routers) - Broadcasts frames periodicall LLDP - Open standard Linu, Cisco, Windos - Identifies an sstem that supports it - Broadcasts frames periodicall