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Archive for the 'Switching' Category

Creating Layer 2 and Layer 3 Ether Channels

Friday, August 28th, 2009

In order to bundle multiple interfaces between switches in an effort in increase throughput, a Ether Channel can be created.   Ether Channels can be created as Layer 2 or Layer3. The obvious difference between the 2 is that a Layer 3 link will have a IP address associated and hence traffic can be routed between [...]

Inter-VLAN Routing (Router on a Stick)

Wednesday, August 12th, 2009

In order for 2 VLANS to be able to communicate, the traffic must be routed. This can be done either by a multi-layer switch which will have routing capabilities, or the packets can be routed by a router.   As an example, I have 2 VLANS, VLAN 10 and VLAN 20 which have subnets 10.0.10.0/24 [...]

VTP (VLAN Trunking Protocol)

Tuesday, August 11th, 2009

VTP (VLAN Trunking protocol) is a protocol used to replicate the VLAN information across switches, however there are a few things that must be made clear…   1/ VLAN information will only be sent on trunk ports 2/ Only the VLAN identity is replicated, NOT which ports are configured to use that VLAN! 3/ Maintains [...]

Speed and Duplex configuration

Monday, August 10th, 2009

Although the configuration of both of these functions is incredible easy, the concept behind them is somewhat important.   Duplex defines how traffic will be sent and can be related to a 2-way radio vs. A telephone. With a 2-way radio, more so when there are more than 2 people on the same radio frequency, [...]

Concept and Configuring VLAN’S

Friday, August 7th, 2009

A VLAN is a Virtual LAN which allows us to logically separate computers on our network.   In previous years, an office would have a physical switch or hub in each office, and offices were structured around the job function. In other words, all sales people would be in the same office and would all [...]

Port Security on a Cisco Switch

Thursday, August 6th, 2009

In order to control what machines are plugged into your network, Cisco introduced the “switchport port-security” command.   In this tutorial I’m going to explain how to use this command, and different options available using it.   Below is the breakdown of the commands I used in the live demo, and an explanation of each. [...]

Configuring a Trunk port on a Cisco Switch

Wednesday, August 5th, 2009

Once VLANS have been defined on a switch and you have placed ports into their corresponding VLANS, traffic is limited to remain inside it’s Virtual LAN. The only way for traffic to leave the switch, is to have it sent on a port that is in the same VLAN as its source, or sent over [...]

Configuring an Access port on a Cisco switch

Tuesday, August 4th, 2009

Almost 100% of Cisco switches will have a 50 second delay on a port before it goes live. What this means, is that when you plug a new device into a switch such as a PC, there will be a 50 second delay before the port will become active and the PC will be able [...]

Configuring an IP address and Default-Gateway on a Cisco Switch

Monday, August 3rd, 2009

The configuration of an IP address on a switch is slightly different from a router. On a router we configure the IP address on the physical interface, however on a switch the physical interfaces are running at Layer 2 and hence don’t have IP addresses configured on them.   Even though a switch does not [...]

Configuring SPAN on a Cisco Switch

Friday, July 31st, 2009

SPAN (Switched Port Analyser) is a requirement whenever you have a system that wishes to log and monitor traffic that is passing through a switch. Since a switch only sends traffic to the machine requiring the packets, adding a sniffer to the switch would result in you only seeing traffic to your sniffer, from your [...]