Aug 22, 2011
Jun 6, 2011
CCNA Academic Class Labs Semester One
- Course Introduction
- Module 1: Building a Simple Network
- Module 2: Ethernet LANs
- Module 3: WLANs
- Module 4: LAN Connections
- Module 5: WAN Connections
- Module 6: Network Environment Management Capstone Lab: Network Environment Management Lab Guide
May 29, 2011
Cisco Router Configuration Tutorial (Part-1)
All the show commands a available in the current mode. Definitely try out the following commands:
Router#show interfaces
Router#show ip protocols
Router#show ipv6 protocols
Router#show ip route
Router#show ipv6 route
Router#show ip arp
Router#show ipv6 neighborsGlobal configuration (config)
In the parent mode, you issue the command
config.
Router#config
Router(config)#
You do this in configuration mode with the hostname command.
Router(config)#hostname ExampleName
ExampleName(config)# Another useful command issued from config mode is the command to designate the DNS server to be used by the router:
ExampleName(config)#ip name-server aa.bb.cc.dd
ExampleName(config)#ctrl-Z
ExampleName# This is also where you set the password for privileged mode.
ExampleName(config)#enable secret examplepassword
ExampleName(config)#ctrl-Z
ExampleName# Until you hit ctrl-Z (or type exit until you reach parent mode) your command has not been put into affect. You can enter config mode, issue several different commands, then hit ctrl-Z to activate them all. Each time you hit ctrl-Z you return to parent mode and the prompt:
ExampleName#
Configuring Cisco router interfaces
Cisco interface naming is straightforward. Individual interfaces are referred to by this convention:
media type slot#/port#
Therefor, to display the configuration of that interface you use the command:
ExampleName#show interface ethernet 6/2 If your router does not have slots, like a 1600, then the interface name consists only of:
media type port# For example:
ExampleName#show interface serial 0 Here is an example of configuring a serial port with an IP address:
ExampleName#config
ExampleName(config)#interface serial 1/1
ExampleName(config-if)#ip address 192.168.155.2 255.255.255.0
ExampleName(config-if)#ipv6 address fe80::230:1bff:fe80:b8ea/64
ExampleName(config-if)#ipv6 enable
ExampleName(config-if)#no shutdown
ExampleName(config-if)#ctrl-Z
ExampleName# Then to verify configuration:
ExampleName#show interface serial 1/1
Configuring Cisco Routing
IP routing is automatically enabled on Cisco routers. If it has been previously disabled on your router, you turn it back on in config mode with the command ip routing.
ExampleName(config)#ip routing
ExampleName(config)#ctrl-Z To enable IPv6 routing, use the command ipv6 unicast-routing.
ExampleName(config)#ipv6 unicast-routing
ExampleName(config)#ctrl-Z There are two main ways a router knows where to send packets. The administrator can assign static routes, or the router can learn routes by employing a dynamic routing protocol.
In the Cisco IOS this is done with the ip route and ipv6 route commands.
ExampleName#config
ExampleName(config)#ip route 172.16.0.0 255.255.255.0 192.168.150.1
ExampleName(config)#ctrl-Z
ExampleName#show ip route
ExampleName#config
ExampleName(config)#ipv6 route fe80::230:1bff:fe80::/64 fe80::230:1bff:fe80::1
ExampleName(config)#ctrl-Z
ExampleName#show ipv6 route
Saving your Cisco Router configuration
If you turned the router off right now, and turned it on again, you would have to start configuration over again. Your running configuration is not saved to any perminent storage media. You can see this configuration with the command show running-config.
ExampleName#show running-config You do want to save your successful running configuration. Issue the command copy running-config startup-config.
ExampleName#copy running-config startup-config Your configuration is now saved to non-volatile RAM (NVRAM). Issue the command show startup-config.
ExampleName#show startup-config Now any time you need to return your router to that configuration, issue the command copy startup-config running-config.
ExampleName#copy startup-config running-config
Example Cisco Router configuration
- Router>enable
- Router#config
- Router(config)#hostname N115-7206
- N115-7206(config)#interface serial 1/1
- N115-7206(config-if)ip address 192.168.155.2 255.255.255.0
- N115-7206(config-if)ipv6 address fe80::230:1bff:fe80:b8ea/64
- N115-7206(config-if)ipv6 enable
- N115-7206(config-if)no shutdown
- N115-7206(config-if)ctrl-z
- N115-7206#show interface serial 1/1
- N115-7206#config
- N115-7206(config)#interface ethernet 2/3
- N115-7206(config-if)#ip address 192.168.150.90 255.255.255.0
- N115-7206(config-if)#no shutdown
- N115-7206(config-if)#ctrl-z
- N115-7206#show interface ethernet 2/3
- N115-7206#config
- N115-7206(config)#ip name-server 172.16.0.10
- N115-7206(config)#ctrl-z
- N115-7206#ping archie.au
- N115-7206#config
- N115-7206(config)#enable secret password
- N115-7206(config)#ctrl-z
- N115-7206#copy running-config startup-config
- N115-7206#exit
You are already familiar with the show commands, both specific commands and how to learn what other show commands are available. Some of the most basic, most useful commands you will use for troubleshooting are:
Router#show interfaces
Router#show ip protocols
Router#show ipv6 protocols
Router#show ip route
Router#show ipv6 route
Router#show ip arp
Router#show ipv6 neighbors
References
Feb 23, 2011
How to Setup VLAN Trunking Protocol (VTP) on Cisco Switches ?
How can VTP help me?
Say that you have 20 switches in your large office building. On each of these switches, you have four VLAN’s. Without VTP, you have to create each of these four VLANs on each of these switches. With VTP, you only have to create the four VLANs once, on one switch, and all other switches learn about the four VLANs.
In other words, the job of VTP is to distribute VLAN configuration information between all the switches.
How does it work?
The job of VTP is best explained from the perspective of the VTP server. All switches, by default, are VTP servers. The VTP server is where you would create, remove, or modify VLANs.
This VTP server sends an advertisement, across the domain, every 5 minutes or whenever a change is made in the VLAN database. That advertisement contains all the different VLAN names, VLAN numbers, what switches have ports in what VLANs, and a revision number. Whenever a switch receives an update with a larger revision number than the last one it applied, it applies that revision.
Keep in mind that VTP is a Cisco proprietary protocol. So, to use VTP between your switches, you must have all Cisco switches.
VTP Modes
VTP switches can be in three different modes. Those modes are:
-
Server – the default where all VLAN adds, changes, and removals are allowed
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Client – where no changes can be made, only new revisions can be received from the VTP server switches.
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Transparent – where local VLAN information can be changed but that information is not sent out to other switches. Transparent switches also do not apply VTP advertisements from other switches but they do forward those advertisements on.
Usually, you would want a few of your core switches to be servers and all remaining remote or access layer switches to be clients. You would only make changes on the server switches and those changes would be propagated to the client switches.
What about pruning?
VTP pruning is the process of not sending IP broadcast traffic for certain VLANs to switches that do not have any ports in that VLAN. The switches that choose not to send these broadcasts know that they can not do this because of VTP. With VTP telling them what ports the other switches have, this switch knows that they don’t have to send them broadcast packets, because they know that the other switches don’t need them.
Pruning saves LAN bandwidth because broadcasts don’t have to be sent to switches that don’t need them.
How do you configure VTP?
To configure VTP, you use the vtp global configuration mode command. With this command you can specify the following:
-
VTP domain – the name of the VTP domain. All switches communicating with VTP in the same domain, must have the same VTP domain name.
-
VTP mode – either server, client, or transparent
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VTP password – a password to control who can and cannot receive VTP information
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VTP pruning – VTP pruning is either turned on or off
Here is a sample configuration:
To see what is going on with VTP, you can use show vtp status, like this:
Article Summary
In summary, here is what we have learned:
-
VTP is used to distribute VLAN configuration information between switches
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VTP is Cisco proprietary and can only be used on Cisco switches.
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By using VTP, you can also prune your VLANs, saving bandwidth
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The command to configure VTP is the global configuration mode command, vtp
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The command to check status is the privileged mode command, show vtp status.
What is a VLAN? How to Setup a VLAN on a Cisco Switch ?
Have you ever wondered what a Virtual LAN (or VLAN) is or been unclear as to why you would want one? If so, I have been in your place at one time too. Since then, I have learned a lot about what a VLAN is and how it can help me. In this article, I will share that knowledge with you.
What is a LAN?
Okay, most of you already know what a LAN is but let’s give it a definition to make sure. We have to do this because, if you don’t know what a LAN is, you can’t understand what a VLAN is.
A LAN is a local area network and is defined as all devices in the same broadcast domain. If you remember, routers stop broadcasts, switches just forward them.
What is a VLAN?
As I said, a VLAN is a virtual LAN. In technical terms, a VLAN is a broadcast domain created by switches. Normally, it is a router creating that broadcast domain. With VLAN’s, a switch can create the broadcast domain.
This works by, you, the administrator, putting some switch ports in a VLAN other than 1, the default VLAN. All ports in a single VLAN are in a single broadcast domain.
Because switches can talk to each other, some ports on switch A can be in VLAN 10 and other ports on switch B can be in VLAN 10. Broadcasts between these devices will not be seen on any other port in any other VLAN, other than 10. However, these devices can all communicate because they are on the same VLAN. Without additional configuration, they would not be able to communicate with any other devices, not in their VLAN.
Are VLANs required?
It is important to point out that you don’t have to configure a VLAN until your network gets so large and has so much traffic that you need one. Many times, people are simply using VLAN’s because the network they are working on was already using them.
Another important fact is that, on a Cisco switch, VLAN’s are enabled by default and ALL devices are already in a VLAN. The VLAN that all devices are already in is VLAN 1. So, by default, you can just use all the ports on a switch and all devices will be able to talk to one another.
When do I need a VLAN?
You need to consider using VLAN’s in any of the following situations:
- You have more than 200 devices on your LAN
- You have a lot of broadcast traffic on your LAN
- Groups of users need more security or are being slowed down by too many broadcasts?
- Groups of users need to be on the same broadcast domain because they are running the same applications. An example would be a company that has VoIP phones. The users using the phone could be on a different VLAN, not with the regular users.
- Or, just to make a single switch into multiple virtual switches.
Why not just subnet my network?
A common question is why not just subnet the network instead of using VLAN’s? Each VLAN should be in its own subnet. The benefit that a VLAN provides over a subnetted network is that devices in different physical locations, not going back to the same router, can be on the same network. The limitation of subnetting a network with a router is that all devices on that subnet must be connected to the same switch and that switch must be connected to a port on the router.
With a VLAN, one device can be connected to one switch, another device can be connected to another switch, and those devices can still be on the same VLAN (broadcast domain).
How can devices on different VLAN’s communicate?
Devices on different VLAN’s can communicate with a router or a Layer 3 switch. As each VLAN is its own subnet, a router or Layer 3 switch must be used to route between the subnets.
What is a trunk port?
When there is a link between two switches or a router and a switch that carries the traffic of more than one VLAN, that port is a trunk port.
A trunk port must run a special trunking protocol. The protocol used would be Cisco’s proprietary Inter-switch link (ISL) or the IEEE standard 802.1q.
How do I create a VLAN?
Configuring VLAN’s can vary even between different models of Cisco switches. Your goals, no matter what the commands are, is to:
- Create the new VLAN’s
- Put each port in the proper VLAN
Let’s say we wanted to create VLAN’s 5 and 10. We want to put ports 2 & 3 in VLAN 5 (Marketing) and ports 4 and 5 in VLAN 10 (Human Resources). On a Cisco 2950 switch, here is how you would do it:
At this point, only ports 2 and 3 should be able to communicate with each other and ports 4 & 5 should be able to communicate. That is because each of these is in its own VLAN. For the device on port 2 to communicate with the device on port 4, you would have to configure a trunk port to a router so that it can strip off the VLAN information, route the packet, and add back the VLAN information.
What do VLAN’s offer?
VLAN’s offer higher performance for medium and large LAN’s because they limit broadcasts. As the amount of traffic and the number of devices grow, so does the number of broadcast packets. By using VLAN’s you are containing broadcasts.
VLAN’s also provide security because you are essentially putting one group of devices, in one VLAN, on their own network.
Article Summary
Here is what we have learned:
- A VLAN is a broadcast domain formed by switches
- Administrators must create the VLAN’s then assign what port goes in what VLAN, manually.
- VLAN’s provide better performance for medium and large LAN’s.
- All devices, by default, are in VLAN 1.
- A trunk port is a special port that runs ISL or 802.1q so that it can carry traffic from more than one VLAN.
- For devices in different VLAN’s to communicate, you must use a router or Layer 3 switch.
- Even if you've worked on Cisco networks for a while, be sure to check out TrainSignal's.