CCNA Guide to Cisco Networking

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Objectives. Explain the features and benefits of Fast EthernetDescribe the guidelines and distance limitations of Fast EthernetDefine full- and half-duplex Ethernet operationsDistinguish between cut-through, fragment-free, and store-and forward LAN switchingDefine the operation of the Spanning Tree Protocol and its benefits.

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CCNA Guide to Cisco Networking

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1. CCNA Guide to Cisco Networking Chapter 13: Switching and VLANs

2. Objectives Explain the features and benefits of Fast Ethernet Describe the guidelines and distance limitations of Fast Ethernet Define full- and half-duplex Ethernet operations Distinguish between cut-through, fragment-free, and store-and forward LAN switching Define the operation of the Spanning Tree Protocol and its benefits

3. Objectives (continued) Describe the benefits of virtual LANs Understand the purpose of the VLAN trunking protocol (VTP)

4. Ethernet Operations CSMA/CD Listen to wire before transmitting Contention mention Interframe gap Also known as an interpacket gap 9.6 seconds Collisions Simultaneous frame transmission 32-jam signal Back-off period

5. Ethernet Operations (continued) CSMA/CD (continued) Collision domain Physical topology segment in which frames may collide Layer 3, layer 2, and layer 1 Repeaters and hubs do not microsegment Switches and bridges microsegment at layer 2 Routes and gateways segment at layer 2 and layer 3

6. Latency Latency Sometimes referred to as propagation delay Length of time to forward, send, or propagate a data frame Bit time Slot time 5-4-3 rule Latency differs depending on Resistance of transmission medium Number of nodes Amount of processing of packet

7. Latency (continued)

8. Ethernet Errors Most errors are caused by Defective equipment Incorrectly configured equipment Frame size errors Frame size minimum 64 bytes Frame size maximum 1518 bytes

9. Ethernet Errors (continued) Frame error classification Short frame or runt Long frame or giant Jabber Frame check sequence error Alignment error

10. Collision Errors As the number of devices increase so does the number of collisions Late collisions Violate the 5-4-3 rule Cable too long Slot time exceeded Segment with a router Microsegment with a switch or bridge Transmitting station will attempt to retransmit 16 times Additional collision detections will be considered a NIC error

11. Broadcasts Nodes establishing a presence Applications advertising a service IP address-to-MAC address resolution Broadcast storm Network loop 126 or more broadcasts per second Possible solutions Reduce the number of services on servers Limit the number of protocols

12. Fast Ethernet 100 Mbps 10/100 Autosense Full-duplex or half-duplex Category 5 or higher cable IEEE 802.3u implementations 100Base-TX 100Base-T4 100Base-FX

13. Half- And Full-Duplex Communication Half-duplex Send and receive signals separately Full-duplex Send and receive simultaneously No collisions Benefits of full-duplex No collisions No retransmissions Full bandwidth in both directions No waiting for other transmissions

14. Half- And Full-Duplex Communication (continued) Four different duplex options on 2950 switch Auto Full Full-flow control Half

15. Half- And Full-Duplex Communication (continued)

16. LAN Segmentation Segmenting with bridges Filter traffic at Data Link layer Segment LAN into 2 or 3 major segments Bridges build a MAC-to-segment table Manual configuration Learn from source MAC of arriving frame Bridges forward frames through the bridge when the destination of the frame is on a different segment

17. LAN Segmentation (continued) Points to remember about bridges Reduce collisions No effect on broadcasts or multicasts Extend physical length of LAN Efficient use of bandwidth

18. Segmenting With Routers Points to remember when segmenting with routers Forwards packets based on layer 3 addresses Decrease collisions Reduce broadcast and multicast traffic Support multiple paths and routes between routers Efficient use of bandwidth for the newly created segments

19. Segmenting With Routers (continued) Points to remember when segmenting with routers (continued) Increase security Increase the physical distance of the network Provide layer 3 routing, packet fragmentation and reassembly, and traffic flow control Provide communications between different technologies such as Ethernet and Token Ring or Ethernet and Frame Relay Higher latency than bridges

20. LAN Switching Segmentation with switches Switches are hardware controlled Bridges are software controlled Microsegmentation Switched bandwidth Shared bandwidth Efficient use of bandwidth Able to connect segments of different speeds 10 Mbps to 100 Mbps 100 Mbps to 1Gbps

21. LAN Switching (continued)

22. LAN Switching (continued)

23. Switch Operations MAC-to-switch port mapping Content-addressable memory (CAM) Learns MAC addresses automatically Source address from arriving frame Two types of memory buffering Port-based memory buffering Shared-memory buffering Symmetric and asymmetric switching

24. Securing Switch Ports Configure a permanent MAC address Does not have a TTL Define a static map entry Restricts communication between specific ports Set a limit on the number of MAC addresses Define the action when a security violation occurs

25. Switching Methods Four methods for processing and forwarding frames Store-and-forward Read the entire frame Fragment-free Reads first 64 bytes Lower latency than store-and-forward Also known as “modified cut-through” Minor error detection

26. Switching Methods (continued) Four methods for processing and forwarding frames (continued) Cut-through Forwards frame after destination MAC is read First 14 bytes of frame Lowest latency No error detection Adaptive cut-through Error sensing Uses cut-through and store-and-forward

27. Switching Methods (continued)

28. Switching Methods (continued)

29. Switching Methods (continued)

30. Spanning Tree Protocol Spanning Tree Protocol (STP) Physical loops Logical loops Spanning Tree Algorithm (STA) IEEE 802.1d

31. Spanning Tree Protocol (continued)

32. Spanning Tree Protocol (continued) Build a logical path Election process Root bridge (root device) Bridge protocol data units (BPDU) or Configuration bridge protocol data units (CBPDU) Root ports

33. Spanning Tree Protocol (continued) Port states Stable states Blocking: Send and receive BPDUs but no data frames Forwarding: Send and receive all data frames and learn new MAC addresses Disabled: No frames sent or received Transitory states Listening: Listening to election process only Learning: Learning new MAC addresses

34. Spanning Tree Protocol (continued) STP switch port process From bridge/switch bootup to blocking From blocking to listening (or to disabled) From listening to learning (or to disabled) From learning to forwarding (or to disabled) From forwarding to disabled (automatically or manually) Topology changes

35. Virtual LANs Logical grouping of network devices and nodes Broadcast domain Management VLAN Also known as default VLAN Cannot be deleted Every port is on VLAN 1 by default Router are required to move traffic between VLANs

36. Virtual LANs (continued)

37. Virtual LANs (continued)

38. Benefits of VLANs VLANS provide the following benefits It is easier to add and move stations on the LAN It is easier to reconfigure the LAN There is better traffic control There is increased security

39. Dynamic vs. Static VLANs VLANs can be configured dynamically or statically Static VLANs are configured port-by-port Dynamic VLAN ports automatically learn their VLAN assignment Software database of MAC address-to-VLAN mappings

40. VLAN Standardization Frame filtering Frames can be separated into VLANs MAC addresses Network-layer protocol type Application type Frame tagging IEEE 802.1q Also known as frame identification Adds a four-byte field to Ethernet frame Inter-Switch Link (ISL) protocol Cisco proprietary frame-tagging method 26 byte header

41. Creating VLANs VLAN configuration Rm410HL#vlan database Rm410(vlan)#vtp domain hudlogic Rm410(vlan)#vtp server Rm410(vlan)#vlan 2 name production Rm410(vlan)#vlan 3 name accounting Rm410(vlan)#vlan 4 name marketing

42. Creating VLANs (continued) VLAN configuration (continued) Rm410#configure terminal Rm410(config)#interface f0/1 Rm410(config-if)#switchport mode trunk Rm410(config-if)#exit Rm410(config)#interface f0/2 Rm410(config-if)#switchport access vlan 1

43. Link Types And Configuration Two types of links Trunk links Switch-to-switch links Switch-to-router links 100 Mbps links 1 Gbps links Access links Non-VLAN aware devices

44. Link Types And Configuration (continued) Trunk links have five states Auto Desirable Non-negotiate Off On Rm410(config)#interface f0/1 Rm410(config-if)#switchport mode trunk

45. Trunking Protocol VLAN trunking protocol Layer 2 messaging protocol Manages all changes to the VLANs across networks VTP domains VTP devices are organized in to domains Switches can only belong to one domain Rm410HL#vlan database Rm410(vlan)#vtp domain hudlogic

46. Trunking Protocol (continued) VTP device modes Server Rm410(vlan)# vtp server Client Rm410(vlan)# vtp client Transparent Rm410(vlan)# vtp transparent Default to server mode VTP pruning Reduces the number of VTP updates on trunk link Rm410(vlan)# vtp pruning

47. Trunking Protocol (continued) Delete VLAN database Rm410# delete flash:vlan.dat Switch interface descriptions Rm410HL(config)#int f0/1 Rm410HL(config-if)#description productionVLAN Nonswitching hubs and VLANs

48. Routers and VLANs Increase security Manage traffic between VLANs Subinterfaces Access-lists Router-on-a-stick

49. Routers and VLANs (continued) Enable inter-VLAN communication between VLAN 1 and VLAN 2 Router(config)# interface e0.1 Router(config-subif)# ip address 164.106.1.1 255.255.255.0 Router(config-subif)# encapsulation isl 1 Router(config-if)# exit Router(config)# interface e0.2 Router(config-subif)# ip address 164.106.2.1 255.255.255.0 Router(config-subif)# encapsulation isl 2

50. Routers and VLANs (continued)

51. Summary Ethernet (CSMA/CD) is a media access method that was developed in the 1960s Stations on an Ethernet LAN must listen to the network media before transmitting to ensure that no other station is currently transmitting If two stations transmit simultaneously on the same collision domain, a collision will occur The transmitting stations must be able to recognize the collision and ensure that other stations know about the collision by transmitting a jam signal Once the jam signal has cleared the network, other stations can begin transmitting, but the stations that caused the collision must wait for a random backoff period before attempting to transmit again

52. Summary (continued) The delays caused by collisions on a network can seriously affect performance when collisions exceed 5% of the traffic on the collision domain One way to reduce the number of collisions on a network is to segment the network with a bridge, switch, or router Switches do the most to divide the collision domain and reduce traffic without dividing the broadcast domain This means that the LAN segment still appears to be a segment when it comes to broadcast and multicast traffic

53. Summary (continued) Switches microsegment unicast traffic by routing frames directly from the incoming port to the destination port This means that packets sent between two hosts on a LAN segment do not interrupt communication of other hosts on the segment Switches are therefore able to increase the speed at which communications occur between multiple hosts on the segment Another way to increase the speed at which a LAN operates is to upgrade from Ethernet to Fast Ethernet This allows you to increase the speed at which frames are transferred on the wire, thereby increasing the performance of the network

54. Summary (continued) To fully implement Fast Ethernet, you have to replace all the hubs, NICs, and any other network interfaces with interfaces that support Fast Ethernet Several Fast Ethernet devices allow for compatibility between Fast Ethernet and standard Ethernet, but to take full advantage of Fast Ethernet, all components must be upgraded Full duplex can also improve Ethernet performance over half-duplex operations because no collisions can occur on a full-duplex LAN Full duplex also allows frames to be sent and received simultaneously, which makes a 10-Mbps full-duplex connection seem like two 10-Mbps half-duplex connections

55. Summary (continued) Full-duplex operations are only supported by devices designed for this type of communication This means that the half-duplex devices on a network will have to be completely replaced to take advantage of the speed offered by full-duplex operations The Spanning Tree Protocol (STP), which is enabled by default on most bridges and switches, allows administrators to create physical loops between bridges and switches without creating logical loops that would pose a problem for packet delivery Another way to increase the performance, flexibility, and security of a network is to implement VLANs via switches

56. Summary (continued) VLANs are separate broadcast domains that are not limited by physical configurations, instead a VLAN is a logical broadcast domain implemented via one or more switches Performance benefits associated with VLANs are derived from limiting the amount of broadcast traffic that would naturally pass through a switch without filtration The enhanced flexibility to assign any port on any switch to a particular VLAN makes moving, adding, and changing network configurations easier VLAN information is communicated to switches using the VLAN trunking protocol (VTP)

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