CN2668 Routers and Switches (V2)

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CN2668 Routers and Switches (V2). Kemtis Kunanuraksapong MSIS with Distinction MCTS, MCDST, MCP, A+. Agenda. Chapter 13: Advanced Switching Concepts Exercise Quiz. Spanning Tree Protocol. Physical path loops - PowerPoint PPT Presentation

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CN2668Routers and Switches (V2)Kemtis KunanuraksapongMSIS with DistinctionMCTS, MCDST, MCP, A+

AgendaChapter 13: Advanced Switching ConceptsExerciseQuiz2Spanning Tree ProtocolPhysical path loopsA physical connection created when connected with two or more physical media linksHelp improve a networks fault toleranceDrawbackCan result in endless packet loopingSee Figure 13-1 on Page 366Spanning Tree Protocol (STP)A layer 2 link management protocol designed to prevent looping on bridges and switchesThe specification for STP is IEEE 802.1d3Spanning Tree Protocol (continued)Spanning Tree Algorithm (STA)To interrupt the logical loop created by a physical loop in a bridged/switched environmentSome or certain ports on are configured to discard the framesBuilding a logical pathSwitches and bridges on a network use an election process to configure a single logical pathA root bridge (root device) is selectedThen, the other switches and bridges configure their ports, using the root bridge as a point of referenceThe decision based on the lowest number of priority or lowest MAC address if both have same priority number4Spanning Tree Protocol (continued)Bridges use STP to transfer the information about each bridges MAC address and priority numberBridge protocol data units (BPDU) or Configuration bridge protocol data units (CBPDU)The messages the devices send to one anotherEach bridge or switch determines which of its own ports offers the best path to the root bridgeRoot portsThe BPDU messages are sent between the root bridge and the best ports on the other devices5Spanning Tree Protocol (continued)If BPDUs are not received for a certain period of timeThe non-root-bridge devices will assume that the root bridge has failed, and a new root bridge will be electedOnce the root bridge is determined and the switches and bridges have calculated their paths to the root bridgeThe logical loop is removed by one of the switches or bridges

6Spanning Tree Protocol (continued)Port statesSTP will cause the ports on a switch or bridge to settle into a stable stateStable statesThe normal operating states of portsTransitory statesPrevent logical loops during a period of transition from one root bridge to another while a new root bridge is being elected

7Spanning Tree Protocol (continued)The stable states are as follows:BlockingSend and receive STP messages, not the data framesForwardingReceive and send all data frames, STP messages, and learn new MAC addressDisabledThe transitory states are as follows:ListeningLearning8Spanning Tree Protocol (continued)Ports on STP-enabled devices move through the different states as indicated in the following list:From bridge/switch bootup to blockingFrom blocking to listening (or to disabled)From listening to learning (or to disabled)From learning to forwarding (or to disabled)From forwarding to disabled9Spanning Tree Protocol (continued)Topology changesWhen the topology is changed, STP-enabled devices react automaticallyIf CBPDUs are not received, Device will claim to be the root bridge and continue the path build processPer-VLAN STP (PVSTP)Operates on VLANs and treats all VLANs connected as separate physical networks10Spanning Tree Protocol (continued)Spanning Tree PortFastAllows you to configure a switch to bypass some of the latency (delay)Only if that device will not create the loopConfiguring STPSee Table 13-1 on Page 369Rapid STP (RSTP)Use IEEE 802.1w11Virtual LANsA grouping of network devices that is not restricted to a physical segment or switchCan be configured on most switches to restructure broadcast domainsBroadcast domainGroup of network devices that will receive LAN broadcast traffic from each other12Virtual LANs (continued)Management VLAN (also known as the default VLAN)By default, every port on a switch is in VLAN 1You can create multiple VLANs on a single switch Or create one VLAN across multiple switchesA VLAN is a layer 2 implementation, and does not affect layer 3 logical addressingSee Figure 13-2 and 13-3 on Page 37113Benefits of VLANsBenefits:Ease of adding and moving stations on the LANEase of reconfiguring the LANBetter traffic controlBecause the administrator can set the size of the broadcast domainIncreased securityVLANs can be configured by network administrators to allow membership only for certain devicesSee Figure 13-4 on Page 373

14Dynamic vs. Static VLANsStatic VLANsConfigured port-by-portThe network administrator manually types in the mapping for each port and VLANDynamic VLANUses a software database of MAC address-to-VLAN mappings that is created manuallyPorts can automatically determine their VLAN configuration

15VLAN StandardizationFrame filteringOne table for each VLANMaster table that was shared by all VLANsFrame taggingAlso known as frame identificationIEEE 802.1q specification16VLAN Standardization (continued)Frame taggingInvolves adding a four-byte field to the actual Ethernet frame to identify the VLAN and other pertinent informationMakes it easier and more efficient to ship VLAN frames across network backbonesSwitches on the other side of the backbone can simply read the frame instead of being required to refer back to a frame-filtering tableInter-Switch Link (ISL) protocolCisco-based that supports only17Creating VLANsTo use the config-vlan mode, you type the following:Rm410HL(config)#VLAN 2Rm410HL(config-vlan)name productionTo use the VLAN configuration mode, you start by entering the VLAN databaseRm410HL #VLAN databaseRm410HL(vlan)#vlan 2 name production18Creating VLANs (continued)To assign switch ports to the new VLANsPorts can be assigned as static or dynamicRm410HL(config)#int f0/5Rm410HL(config-if)#switchport access vlan 2To remove a VLAN, use the no parameter:Rm410HL(config)#no vlan 219Link Types and ConfigurationTrunk linksSwitch-to- switch or switch-to-router links that can carry traffic from multiple VLANsAccess linksLinks to non-VLAN-aware devices such as hubs and individual workstations20Link Types and Configuration (continued)5 different states for a trunk link:Auto if connected device is set to on or desireableDesirable if connected device is set to on or desireable, or autoNonegotiate will not negotiate that status with any other deviceOff is not a trunk interface and will try to disableOn is not a trunk interface and will try to disable

21Link Types and Configuration (continued)To configure a trunk link on a Catalyst 2950Rm401HL# Conf tRm401HL(config)# int fastethernet 0/24Rm401HL(config-if)# switchport mode trunkYou can prevent ports from using VLANRm401HL# Conf tRm401HL(config)# int fastethernet 0/24Rm401HL(config-if)# switchport trunk allowed vlan remove 4

22Link Types and Configuration (continued)Switch interface descriptionsYou can configure a name for each port on a switchRm401HL# Conf tRm401HL(config)# int f0/1Rm401HL(config-if)# description productionVlanRm401HL(config-if)# int f0/24Rm401HL(config-if)# description trunkbldg777

23VLAN Trunking ProtocolTo manage all of the configured VLANs that traverse trunks between switchesA layer 2 messaging protocolVTP domainsVTP devices are organized into domainsEach switch can only be in one VTP domain at a timeAll devices that need to share information must be in the same VTP domainRm410HL#vlan databaseRm410HL(vlan)#vtp domain domainname

24VTP Device ModesServerDevice can add, rename, and delete VLANs and propagate those changes to the rest of the VTP devicesClientDevice is not allowed to make changes to the VLAN structure, but it can receive, interpret, and propagate changes made by a serverTransparentA device is not participating in VTP communications, other than to forward that information through its configured trunk links25VLAN Trunking Protocol (continued)VTP pruning optionReduces the number of VTP updates that traverse a linkOff by default on all switchesIf you turn VTP pruning onVTP message broadcasts are only sent through trunk links that must have the informationVLAN 1 is not eligible to be pruned because it is an administrative (and default) VLAN26Nonswitching Hubs and VLANsImportant considerations:All the systems attached to the hub will be in the same VLANYou will have to physically attach the device to another hub or switch port to change its VLAN assignment, if you move the device27Routers and VLANsTo increase securityMust be used to manage traffic between different VLANsImplement access listsIncrease inter-VLAN securityA router allows restrictions to be placed on station addresses, application types, and protocol types28Routers and VLANs (continued)The router will accept the frame tagged by the sending VLAN and determine the best path to the destination addressThe router will then switch the packet to the appropriate interface and forward it to the destination address29CCNA Guide to Cisco Networking Fundamentals, Fourth Edition30Routers and VLANs (continued)Router-on-a-stickIf a single link is used to connect an external router with the switch containing multiple VLANsTrunking is required for inter-VLAN routingTrunking is the process of using either ISL or 802.1q to allow multiple VLAN traffic on the same linkFor instance, an ISL trunk link would encapsulate each packet with the associated VLAN information and allow the router to route the packet accordingly30AssignmentReview Questions1 25Exercise

ExercisePlace 2 switches and 2 workstation, do not connect the cablesOn first switch rename it to server (for easier understanding)Create VLAN as shown on Page 374-375Set the VTP domainServer#vlan databaseServer (vlan)#VTP domain RM403Create the trunk link on Server. See page 376.

ExerciseOn second switch rename it to client (for easier understanding)Connect UTP cable from WS1 to port 5Connect cross-over cable to port 24 on Server and ClientType the following on Client switchesEnableShow vlan