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2. Building Simple Network 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group 3. Objectives Troubleshooting Common switch Media 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group 4. Troubleshooting Common Switch Media Common issues with cabling on a switched network include basic switch configuration issues, negotiating both the speed and duplex of a link from a PC to a switch, and the uncommon switch hardware failures. The most common switch configuration error is not having a port configured into the correct switch membership. By using the show running-config command or show vlan command, you can easily see the port memberships. Always check your VLAN memberships when troubleshooting a command switch issue. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group 5. Troubleshooting Common Switch Media At times, you may find a host is not communicating to a switch because of mismatched speed or duplex issues. This is not as much a problem as it has been in the past because of the better hardware being produced, but it still may show up from time to time. The default on a switch and host is to use 100Mbps full-duplex. If your host or switch port does not support this configuration, you can configure the switch port with the duplex and speed command. The port LED will be green when everything is OK, however, it will be amber if the port is blocked by STP, and it will turn from green to amber when the port experiences errors. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group 6. Describe enhanced switching technologies (including: VTP, RSTP, VLAN, PVSTP, 802.1q) The basic goals of VLAN Trunking Protocol (VTP) are to manage all configured VLANs across a switched internetwork and to maintain consistency throughout that network. VTP allows you to add, delete, and rename VLANsinformation that is then propagated to all other switches in the VTP domain. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 7. Here's a list of some of the cool features VTP has to offer: Consistent VLAN configuration across all switches in the network VLAN trunking over mixed networks, such as Ethernet to ATM LANE or even FDDI Accurate tracking and monitoring of VLANs Dynamic reporting of added VLANs to all switches in the VTP domain Plug and Play VLAN adding 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 8. You should know these three requirements for VTP to communicate VLAN information between switches: The VTP management domain name of both switches must be set the same. One of the switches has to be configured as a VTP server. No router is necessary. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 9. VTP Modes of Operation Server Client Transport 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 10. Server This is the default mode for all Catalyst switches. You need at least one server in your VTP domain to propagate VLAN information throughout that domain. Also important: The switch must be in server mode to be able to create, add, and delete VLANs in a VTP domain. VTP information has to be changed in server mode, and any change made to a switch in server mode will be advertised to the entire VTP domain. In VTP server mode, VLAN configurations are saved in NVRAM. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 11. Client In client mode, switches receive information from VTP servers, but they also send and receive updates, so in this way, they behave like VTP servers. The difference is that they can't create, change, or delete VLANs. Plus, none of the ports on a client switch can be added to a new VLAN before the VTP server notifies the client switch of the new VLAN. Also good to know is that VLAN information sent from a VTP server isn't stored in NVRAM 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 12. So basically, a switch in VTP client mode will forward VTP summary advertisements and process them. This switch will learn about but won't save the VTP configuration in the running configuration, and it won't save it in NVRAM. Switches that are in VTP client mode will only learn about and pass along VTP informationthat's it! 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 13. Transparent Switches in transparent mode don't participate in the VTP domain or share its VLAN database, but they'll still forward VTP advertisements through any configured trunk links. They can create, modify, and delete VLANs because they keep their own database one they keep secret from the other switches. Despite being kept in NVRAM, the VLAN database in transparent mode is actually only locally significant. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 14. The whole purpose of transparent mode is to allow remote switches to receive the VLAN database from a VTP server-configured switch through a switch that is not participating in the same VLAN assignments. VTP only learns about normal-range VLANs, with VLAN IDs 1 to 1005; VLANs with IDs greater than 1005 are called extended-range VLANs and they're not stored in the VLAN database. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 15. The switch must be in VTP transparent mode when you create VLAN IDs from 1006 to 4094, so it would be pretty rare that you'd ever use these VLANs. One other thing: VLAN IDs 1 and 1002 to 1005 are automatically created on all switches and can't be removed. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 16. PVST Understand that Cisco switches run what is called Per- VLAN Spanning-Tree (PVST), which basically means that each VLAN runs its own instance of the STP protocol. If we typed show spanning-tree, we'd receive information for each VLAN, starting with VLAN 1. So, say we've got multiple VLANs, and we want to see what's up with VLAN 2we'd use the command show spanning-tree vlan 2. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 17. IEEE 802.1Q Created by the IEEE as a standard method of frame tagging, IEEE 802.1Q actually inserts a field into the frame to identify the VLAN. If you're trunking between a Cisco switched link and a different brand of switch, you've got to use 802.1Q for the trunk to work. The 2960s support only the IEEE 802.1Q trunking protocol, but the 3560s will support both the ISL and IEEE methods. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 18. The Goal Of VLAN In Switched Network By default, routers allow broadcasts to occur only within the originating network, while switches forward broadcasts to all segments. Oh, and by the way, the reason it's called a flat network is because it's one broadcast domain, not because the actual design is physically flat In the next picture you see Host A sending out a broadcast and all ports on all switches forwarding it all except the port that originally received it. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 19. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 20. In the Next picture you seeHost A sending a frame with Host D as its destination. What's important is that, as you can see, that frame is only forwarded out the port where Host D is located. This is a huge improvement over the old hub networks, unless having one collision domain by default is what you really want. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 21. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 22. the largest benefit you gain by having a layer 2 switched network is that it creates individual collision domain segments for each device plugged into each port on the switch. There is another issues which is security This one's real trouble because within the typical layer 2 switched internetwork, all users can see all devices by default. And you can't stop devices from broadcasting, plus you can't stop users from trying to respond to broadcasts.. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 23. But there is workaround which is if you create a virtual LAN (VLAN). You can solve many of the problems associated with layer 2 switching with VLANs, as you'll soon see. Here's a short list of ways VLANs simplify network management: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 24. Here's a short list of ways VLANs simplify network management: Network adds, moves, and changes are achieved with ease by just configuring a port into the appropriate VLAN. A group of users that need an unusually high level of security can be put into its own VLAN so that users outside of the VLAN can't communicate with them. As a logical grouping of users by function, VLANs can be considered independent from their physical or geographic locations. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 25. VLANs greatly enhance network security. VLANs increase the number of broadcast domains while decreasing their size. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 26. Configure, verify, and troubleshoot VLANs Figuring out which users you want in each VLAN is not; it's extremely time-consuming. But once you've decided on the number of VLANs you want to create and established which users you want to belong to each one, it's time to bring your first VLAN into the world. To configure VLANs on a Cisco Catalyst switch, use the global config vlan command. In the following example, I'm going to demonstrate how to configure VLANs on the S1 switch by creating three VLANs for three different departmentsagain, remember that VLAN 1 is the native and administrative VLAN by default: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 27. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group From the preceding, you can see that you can create VLANs from 2 to 4094. This is only mostly true. As I said, VLANs can really only be created up to 1005, and you can't use, change, rename, or delete VLANs 1 and 1002 through 1005 because they're reserved. Troubleshooting Common Switch Media 28. The VLAN numbers above that are called extended VLANs and won't be saved in the database unless your switch is set to VTP transparent mode. You won't see these VLAN numbers used too often in production. Here's an example of setting my S1 switch to VLAN 4000 when my switch is set to VTP server mode (the default VTP mode): 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 29. After you create the VLANs that you want, you can use the show vlan command to check them out. But notice that, by default, all ports on the switch are in VLAN 1. To change the VLAN associated with a port, you need to go to each interface and tell it which VLAN to be a part of. Once the VLANs are created, verify your configuration with the show vlan command (sh vlan for short): 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 30. Assigning Switch port To Vlans You configure a port to belong to a VLAN by assigning a membership mode that specifies the kind of traffic the port carries, plus the number of VLANs to which it can belong. You can configure each port on a switch to be in a specific VLAN (access port) by using the interface switchport command. You can also configure multiple ports at the same time with the interface range command. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 31. Remember that you can configure either static memberships or dynamic memberships on a port. For this book's purpose, I'm only going to cover the static flavor. In the following example, I'll configure interface fa0/3 to VLAN 3. This is the connection from the S1 switch to the HostA device: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 32. We need to set up access port on S1 which is probably the most widely used type of port on production switches that has VLANs configured: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media By starting with the switchport mode access command, you're telling the switch that this is a layer 2 port. You can then assign a VLAN to the port with theBy starting with the switchport mode access command, you're telling the switch that this is a layer 2 port. You can then assign a VLAN to the port with theBy starting with the switchport mode access command, you're telling the switch that this is a layer 2 port. You can then assign a VLAN to the port with the 33. By starting with the switchport mode access command, you're telling the switch that this is a layer 2 port. You can then assign a VLAN to the port with the switchport access command. Remember, you can choose many ports to configure at the same time if you use the interface range command. The dynamic and trunk commands are used for trunk ports exclusively. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 34. The 2960 switch only runs the IEEE 802.1Q encapsulation method. To configure trunking on a Fast Ethernet port, use the interface command trunk [parameter]. It's a tad different on the 3560 switch, and I'll show you that in the next section. The following switch output shows the trunk configuration on interface fa0/8 as set to trunk on: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 35. The following list describes the different options available when configuring a switch interface: switchport mode access I discussed this in the previous section, but this puts the interface (access port) into permanent nontrunking mode and negotiates to convert the link into a nontrunk link. The interface becomes a nontrunk interface regardless of whether the neighboring interface is a trunk interface. The port would be a dedicated layer 2 port. switchport mode dynamic auto This mode makes the interface able to convert the link to a trunk link. The interface becomes a trunk interface if the neighboring interface is set to trunk or desirable mode. This is now the default switchport mode for all Ethernet interfaces on all new Cisco switches. switchport mode dynamic desirable This one makes the interface actively attempt to convert the link to a trunk link. The interface becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto mode. I used to see this mode as the default on some older switches, but not any longer. The default is dynamic auto now. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 36. switchport mode trunk Puts the interface into permanent trunking mode and negotiates to convert the neighboring link into a trunk link. The interface becomes a trunk interface even if the neighboring interface isn't a trunk interface. switchport nonegotiate Prevents the interface from generating DTP frames. You can use this command only when the interface switchport mode is access or trunk. You must manually configure the neighboring interface as a trunk interface to establish a trunk link. Trunking with the Cisco Catalyst 3560 Switch As we have seen how to trunk with 2960 switch lets look at how to trunk with the ciso Catalyst 3560 switch. The configuration is pretty much the same as it is for a 2960, with the exception that the 3560 can provide layer 3 services and the 2960 can't. Plus, the 3560 can run both the ISL and the IEEE 802.1Q trunking encapsulation methodsthe 2960 can only run 802.1Q. With all this in mind, let's take a quick look at the VLAN encapsulation difference regarding the 3560 switch. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 37. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 38. we've got the option to add either the IEEE 802.1Q (dot1q) encapsulation or the ISL encapsulation to the 3560 switch. After you set the encapsulation, you still have to set the interface mode to trunk. Honestly, it's pretty rare that you'd continue to use the ISL encapsulation method. Cisco is moving away from ISLits new routers don't even support it. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 39. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Defining the Allowed VLANs on a Trunk As I've mentioned, trunk ports send and receive information from all VLANs by default, and if a frame is untagged, it's sent to the management VLAN. This applies to the extended range VLANs as well. But we can remove VLANs from the allowed list to prevent traffic from certain VLANs from traversing a trunked link. Here's how you'd do that: Troubleshooting Common Switch Media 40. To remove a range of VLANs, just use a hyphen: S1(config-if)#switchport trunk allowed vlan remove 4-8 If by chance someone has removed some VLANs from a trunk link and you want to set the trunk back to default, just use this command: S1(config-if)#switchport trunk allowed vlan all Or this command to accomplish the same thing: S1(config-if)#no switchport trunk allowed vlan 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 41. Changing or Modifying the Trunk Native VLAN You don't really change Native Vlan1 to something else but if you want you can. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 42. So, we've changed our native VLAN on our trunk link to 40, and by using the show running-config command, we can see the configuration under the trunk link: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media It wouldn't just start working soon you will see all kinds of error showing up in the switch If all switches don't have the same native VLAN configured on the trunk links, then we'll start to receive this error: 43. Actually, this is a good, noncryptic error, so either we go to the other end of our trunk link(s) and change the native VLAN or we set the native VLAN back to the default. Here's how we'd do that: S1(config-if)#no switchport trunk native vlan 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 44. Configure, verify, and troubleshoot interVLAN routing: By default, only hosts that are members of the same VLAN can communicate. To change this and allow inter-VLAN communication, you need a router or a layer 3 switch. I'm going to start with the router approach. To support ISL or 802.1Q routing on a Fast Ethernet interface, the router's interface is divided into logical interfacesone for each VLAN. These are called subinterfaces. From a Fast Ethernet or Gigabit interface, you can set the interface to trunk with the encapsulation command: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 45. The subinterface number is only locally significant, so it doesn't matter which subinterface numbers are configured on the router. Most of the time, I'll configure a subinterface with the same number as the VLAN I want to route. It's easy to remember that way, since the subinterface number is used only for administrative purposes. It's really important that you understand that each VLAN is a separate subnet. True, I knowthey don't have to be. But it really is a good idea to configure your VLANs as separate subnets, so just do that. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 46. Routeron-a-Stick Inter-VLAN Configuration There is one very popular method for inter Vlan routing which is using the method names router on stick. Cisco ICND 2 Exam requires you to know this approach. In a VLAN switched network, only hosts on the same VLAN can communicate. To change this and allow inter-VLAN (hosts from other VLANs) to communicate, you need a router or a layer 3 device. The router or layer 3 device interface port connected to the switch must be configured with logical interfaces called subinterface - one for each VLAN, this is achieved by setting the interface to trunk with encapsulation. Before configuring the router, first configure the switch that it will be connected to. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 47. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Routeron-a-Stick Inter-VLAN Configuration Troubleshooting Common Switch Media 48. From the topology above, VLANs 10 and 20 will be created on switch SW1 using the vlan 10 and vlan 20 commands. Example switch configuration command: SW1#config t SW1(config)#vlan 10 SW1(config-vlan)#vlan 20 SW1(config-vlan)#exit The fastethernet (fa0/3) will be set to trunk mode: SW1(config)#interface fa0/3 SW1(config-if)#switchport mode trunk SW1(config-if)#end 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 49. As seen above, because switch port F0/3 will been Configured as trunk port, you do not have to assign any VLANs to the port. And VLANs 10 and 20 had been created too. You cannot use the switchport mode dynamic auto or switchport mode dynamic desirable commands because the router does not support dynamic trunking protocol. Dont forget save the configuration so that it is not lose after a reload of the switch, use the copy running-config startup-config command in privileged EXEC mode to back up the running configuration to the startup configuration. Next, the Example of router R1 configuration command: R1#config t R1(config)#interface fa0/0.10 R1(config-subif)#encapsulation dot1q 10 R1(config-subif)#ip address 192.168.1.1 255.255.255.0 R1(config-subif)#interface fa0/0.20 R1(config-subif)#encapsulation dot1q 20 R1(config-subif)#ip address 192.168.2.1 255.255.255.0 R1(config-subif)#interface fa0/0 R1(config-if)#no shut R1(config-if)#end 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 50. As you can see from the above, the configuration of multiple subinterfaces is different than when physical interfaces are used. Each subinterface is created using the interface interface_id.Subinterface_id global configuration mode command. After that, VLAN ID is assigned using the encapsulation dot1q vlan_id subinterface configuration mode command. Next, you assign the IP Address for the subinterface using the ip address ip_address subnet_mask subinterface configuration mode command. This process is repeated for all the router subinterfaces that are needed to route between the VLANs configured on the network. Each router subinterface needs to be assigned an IP address on a unique Subnet for routing to occur. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 51. Configure, verify, and troubleshoot VTP All Cisco switches are configured to be VTP servers by default. To configure VTP, first you have to configure the domain name you want to use. And of course, once you configure the VTP information on a switch, you need to verify it. When you create the VTP domain, you have a bunch of options, including setting the domain name, password, operating mode, and pruning capabilities of the switch. Use the vtp global configuration mode command to set all this information. In the following example, I'll set the S1 switch to vtp server, the VTP domain to john, and the VTP password to arnold. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 52. S1#config t S1#(config)#vtp mode server Device mode already VTP SERVER. S1(config)#vtp domain john Changing VTP domain name from null to john S1(config)#vtp password arnold Setting device VLAN database password to arnold S1(config)#do sh S1(config)#do show vtp status VTP Version : 2 Configuration Revision : 0 Maximum VLANs supported locally : 255 Number of existing VLANs : 8 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 53. VTP Operating Mode : Server VTP Domain Name : john VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x15 0x54 0x88 0xF2 0x50 0xD9 0x03 0x07 Configuration last modified by 192.168.24.6 at 3-14-93 15:47:32 Local updater ID is 192.168.24.6 on interface Vl1 (lowest numbered VLAN interface found) 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 54. Please make sure that you remember that all switches are set to VTP server mode by default, and if you want to change any VLAN information on a switch, you absolutely must be in VTP server mode. After you configure the VTP information, you can verify it with the show vtp command as shown in the preceding output. The preceding switch output shows the VTP domain, the VTP password, and the switch's mode. Before we move onward to configuring the Core and the S2 switch with VTP information, take a minute to reflect on the fact that the show vtp status output shows that the maximum number of VLANs supported locally is only 255. Since you can create more than 1,000 VLANs on a switch, this seems like it would definitely be a problem if you have more then 255 switches and you're using VTP. And, well, yes, it is problemif you are trying to configure the 256th VLAN on a switch, you'll get a nice little error message stating that there are not enough hardware resources available, and then it will shut down the VLAN and the 256th VLAN will show up in suspended state in the output of the show vlan command. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 55. Let's go to the Core and S2 switches and set them into the john VTP domain. It is very important to remember that the VTP domain name is case sensitive! VTP is not forgivingone teeny small mistake and it just won't work. Core#config t Core(config)#vtp mode client Setting device to VTP CLIENT mode. Core(config)#vtp domain john Changing VTP domain name from null to john Core(config)#vtp password arnold Setting device VLAN database password to arnold Core(config)#do show vtp status VTP Version : 2 Configuration Revision : 0 Maximum VLANs supported locally : 1005 Number of existing VLANs : 5 VTP Operating Mode : Server 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 56. VTP Domain Name : john VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x2A 0x6B 0x22 0x17 0x04 0x4F 0xB8 0xC2 Configuration last modified by 192.168.10.19 at 3-1-93 03:13:16 Local updater ID is 192.168.24.7 on interface Vl1 (first interface found) S2#config t S2(config)#vtp mode client Setting device to VTP CLIENT mode. S2(config)#vtp domain john Changing VTP domain name from null to john S2(config)#vtp password arnold Setting device VLAN database password to arnold S2(config)#do show vtp status VTP Version : 2 Configuration Revision : 0 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 57. Maximum VLANs supported locally : 1005 Number of existing VLANs : 5 VTP Operating Mode : Client VTP Domain Name : john VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x02 0x11 0x18 0x4B 0x36 0xC5 0xF4 0x1F Configuration last modified by 0.0.0.0 at 0-0-00 00:00:00 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 58. now that all our switches are set to the same VTP domain and password, the VLANs I created earlier on the S1 switch should be advertised to the Core and S2 VTP client switches. Let's take a look using the show vlan brief command on the Core and S2 switch: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 59. Troubleshooting VTP You connect your switches with crossover cables, the lights go green on both ends, and you're up and running! Yeahin a perfect world, right? Don't you wish it was that easy? Well, actually, it pretty much iswithout VLANs, of course. But if you're using VLANsand you definitely should bethen you need to use VTP if you have multiple VLANs configured in your switched network. But here there be monsters: If VTP is not configured correctly, it will not work, so you absolutely must be capable of troubleshooting VTP. Let's take a look at a couple of configurations and solve the problems. Lets look at the problem from the output below: SwitchA#sh vtp status VTP Version : 2 Configuration Revision : 0 Maximum VLANs supported locally : 64 Number of existing VLANs : 7 VTP Operating Mode : Server 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 60. VTP Domain Name : CCNA VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled SwitchB#sh vtp status VTP Version : 2 Configuration Revision : 1 Maximum VLANs supported locally : 64 Number of existing VLANs : 7 VTP Operating Mode : Server VTP Domain Name : CCNP VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 61. So what's happening with these two switches? Why won't they share VLAN information? At first glance, it seems that both servers are in VTP server mode, but that's not the problem. Servers in VTP server mode will share VLAN information using VTP. The problem is that they're in two different VTP domains. SwitchA is in VTP domain CCNA and SwitchB is in VTP domain CCNP. They will never share VTP information because the VTP domain names are configured differently. So what's the fix in this change the switch domain so that they both are in same domain right??? Lets look at the another problem. Now that you know how to look for common VTP domain configuration errors in your switches, let's take a look at another switch configuration: 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 62. SwitchC#sh vtp status VTP Version : 2 Configuration Revision : 1 Maximum VLANs supported locally : 64 Number of existing VLANs : 7 VTP Operating Mode : Client VTP Domain Name : john VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled Questions? Can you create VLAN in switch C ? Answer In the Next slide!!! 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 63. Absolutely not the VTP domain name isn't the important thing in this example. What is critical here is the VTP mode. The VTP mode is client, and a VTP client cannot create, delete, add, or change VLANs, remember? VTP clients only keep the VTP database in RAM, and that's not saved to NVRAM. So, in order to create a VLAN on this switch, you've got to make the switch a VTP server first. Quick fix for this are SwitchC(config)#vtp mode server Setting device to VTP SERVER mode SwitchC(config)#vlan 50 SwitchC(config-vlan)# 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 64. Now take a look at the output from these two switches and determine why SwitchB is not receiving VLAN information from SwitchA: SwitchA#sh vtp status VTP Version : 2 Configuration Revision : 4 Maximum VLANs supported locally : 64 Number of existing VLANs : 7 VTP Operating Mode : Server VTP Domain Name : john VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 65. SwitchB#sh vtp status VTP Version : 2 Configuration Revision : 14 Maximum VLANs supported locally : 64 Number of existing VLANs : 7 VTP Operating Mode : Server VTP Domain Name : john VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled So what's the problem. Is it because both switch is in server mode? Or something else? Answer Next slide 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 66. The problem is not the server mode even if the 2 switch is in server mode they can share VLAN information . The problem here is the revision number. Cisco actually suggests that all switches stay VTP servers and that you just make sure the switch you want to advertise VTP VLAN information has the highest revision number. If all switches are VTP servers, then all of the switches will save the VLAN database. But SwitchB isn't receiving VLAN information from SwitchA because SwitchB has a higher revision number than SwitchA. It's very important that you can recognize this problem. How to Fix it:- The first thing you could do is to change the VTP domain name on SwitchB to another name, then set it back to john, which will reset the revision number to zero (0) on SwitchB. The second approach would be to create or delete VLANs on SwitchA until the revision number passes the revision number on SwitchB. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 67. Configure, verify, and troubleshoot RSTP operation Configuring RSTP actually is as easy as configuring any of our other 802.1d extensions. Considering how much better it is than 802.1d, you'd think the configuration would be more complex, but we're in luckit's not. So, let's turn it on in the Core switch now and see what happens: Core#config t Core(config)#spanning-tree mode ? mst Multiple spanning tree mode pvst Per-Vlan spanning tree mode rapid-pvst Per-Vlan rapid spanning tree mode Core(config)#spanning-tree mode rapid-pvst Core(config)# 1d02h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down 1d02h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 68. The Core switch is now running the 802.1w STP. Let's verify that: Core(config)#do show spanning-tree VLAN0001 Spanning tree enabled protocol rstp Root ID Priority 32769 Address 000d.29bd.4b80 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 000d.29bd.4b80 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Role Sts Cost PrioNbr Type Fa0/5 Desg FWD 19 128.5 P2p Peer(STP) Fa0/6 Desg FWD 19 128.6 P2p Peer(STP) Fa0/7 Desg FWD 19 128.7 P2p Peer(STP) Fa0/8 Desg FWD 19 128.8 P2p Peer(STP) 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 69. I can see on my two other switches that all ports have converged. Once everything was up, everything looked the same. 802.1d and 802.1w seem to be cohabiting with no problem. But, if we were to look under the hood more closely, we'd see that the 802.1w switch has changed from 802.1w BPDUs to 802.1d BPDUs on the ports connecting to the other switches running 802.1d (which is all of them). The S1 and S2 switches believe that the Core switch is actually running 802.1d because the Core reverted to 802.1d BPDUs just for them. And even though the S1 and S2 switches receive the 802.1w BPDUs, they don't understand them, so they simply drop them. However, the Core does receive the 802.1d BPDUs and accepts them from the S1 and S2 switches, now knowing which ports to run 802.1d on. In other words, turning 802.1w on for just one switch didn't really help our network at all! One small annoying issue is that once the Core switch knows to send 802.1d BPDUs out the ports connected to S1 and S2, it won't change this automatically if the S1 and S2 switches were later configured with 802.1wwe'd still need to reboot the Core switch to stop the 802.1d BPDUs. 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media 70. Lesson Learned: Configure, verify, and troubleshoot VLAN operation Configure, verify, and troubleshoot VTP operation Configure, verify, and troubleshoot RSTP operation 8/2/2013 Instructional Design-Computer Networking - Bridges Educational Group Troubleshooting Common Switch Media