Friday, April 2, 2010


On most stackable Switches (like C2950 and C3500), you'll see a Mode button. The System button will be blinking green when it's booting up, and would turn solid green when it's done booting. If the System button turns amber, immediately ship it back. RPS stands for redundant power supply and would be lit green if it's plugged in.
Below RPS, there will be four indicators: Stat, Util, Duplex, Speed. Stat is the default, and if a port is amber, the port is up but line protocol is down. If it's green, then both the port and the protocol is up. The Util light will cause the ports to light up from left to right depending on the traffic going through the switch. The duplex will light up when it's full duplex and not light up when it's half duplex. The speed light will light up when it's 100Mbps, and not light up when it's 10Mbps.

There is no power switch on a Switch, so you would have to unplug the switch to turn it off. When you first boot a switch up, you'll see a lot of # symbols. This means that it's decompressing and copying it to volatile memory so it can be run at a decent speed. Also during boot you'll see the version, model of the switch and the memory available. The process is similar to POST (Power-On Self-Test).

Cisco devices usually partition their memory into two chunks (separated by a "/"). To know the exact memory available, you'll have to add the two sides together. Hitting the enter key or the tab key will allow reprinting of questions or typed information that was shifted by status messages.

In real-life, equipment are typically put in places which are either very very cold or very very hot. One would typically want to first set up remote management to manage the devices remotely from a comfortable location.

Remember that at first when you typed the "en" command, you didn't need to provide any password. To password protect your privileged mode, type this in Global Configuration Mode:
enable secret cisco

Where "cisco" is the password. Typically on a new device, you'll set up the hostname. The hostname is also changed in Global Configuration Mode:
ho C2950

In Switches, you'll be able to break it up into multiple broadcast domains by implementing multiple VLANs. VLANs allow you to split one switch into multiple switches. When you assign a switch an IP address, you need to assign them to one of the SVIs. SVI stands for Switch Virtual Interface.

By default, all ports are in VLAN 1. When you configure the SVI for VLAN 1, you are configuring a virtual interface that ports in VLAN 1 can access. A VLAN SVI is configured similar to an interface. To enter an SVI, use:
in vlan 1

You'll need an SVI set up before you can telnet into a switch. To give it an IP address, use:
ip add

Right now VLAN 1 would be administratively down. Administratively down means that the interface is shut down. To do this, you'll need to type:
no shut

There are two things that can be up or down: State, Line Protocol. The state refers to its Physical State. If state is up, it means that it detects a wire connected and it's able to receive bits from it. However, this is not enough. You'll need Line Protocol to be up for any traffic to actually go through. Line Protocol refers to the layer 2 state, which in this case is Ethernet.

To allow the switch to connect to anything outside its subnet, you'll need to give it a default-gateway. To do this, go to Global Configuration Mode and type in:
ip default-gateway

Note that on a router, you'll have to use this to set up a default gateway:
ip route

Every configuration we did is just saved in volatile memory. It will disappear once you reboot the switch. To make the changes permanent, you'll need to write it into non-volatile memory.

In Cisco equipments, volatile memory is known as the running-config, and non-volatile memory is known as the startup-config. To save the configuration, you'll need to copy the volatile memory into the non-volatile memory:
copy running-config startup-config

Alternately, you can use this:

Save regularly. Whenever you get an error, simply reboot and it'll go back to the last saved configuration.

To see the switch's model, IOS version, memory, processor, uptime and so on, use:
show version

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