Cisco TSHOOT – Top 10 Show Commands

Cisco Router Tips
Top 10 'show' Commands by Tom Lancaster

One of the most important abilities a network administrator can have is the know-how to get information out of his network devices so he can find out what's going on with the network. In most networks, the staple of information gathering has been the "show" commands. Here are my top ten commands to know and love:

1. show version: Start simple; this command gives uptime, info about your software and hardware and a few other details.
2. show ip interface brief: This command is great for showing up/down status of your IP interfaces, as well as what the IP address is of each interface. It's mostly useful for displaying critical info about a lot of interfaces on one easy to read page.
3. show interface: This is the more popular version of the command that shows detailed output of each interface. You'll usually want to specify a single interface or you'll have to hit 'page down' a lot. This command is useful because it shows traffic counters and also detailed info about duplex and other link-specific goodies.
4. show ip interface: This often overlooked command is great for all the configuration options that are set. These include the switching mode, ACLs, header compression, ICMP redirection, accounting, NAT, policy routing, security level, etc. Basically, this command tells you how the interface is behaving.
5. show ip route: This indispensable command shows your routing table, which is usually the primary purpose of the box. Get to know the options on this command.
6. show arp: Can't ping a neighbor? Make sure you're getting an arp entry.
7. show running-config: This is an easy one. It tells you how the box is configured right now. Also, "show startup-config" will tell you how the router will be configured after the next reboot.
8. show port: Similar to the show interface command on routers, this command gives you the status of ports on a switch.
9. show vlan: With the trend toward having lots of VLANs, check this command to make sure your ports are in the VLANs you think they are. Its output is very well designed.
10. show tech-support: This command is great for collecting a lot of info. It basically runs a whole bunch of other show commands, and spits out dozens of pages of detailed output, designed to be sent to technical support. But, it's also useful for other purposes.

Taken From: http://www.thenetworkadministrator.com/ciscoroutertips.htm

Backup a Cisco Config Automatically – Changes ( Archive Method )

Cisco IOS has the ability to save it’s configuration when you run the write memory command.
Here is how:

R1#enable
R1#configure terminal
R1(config)#archive
R1(config-archive)#path tftp://172.16.10.61/sw3725/sw3725.cfg
R1(config-archive)#write-memory
R1(config-archive)#exit
R1(config)#exit

The “write-memory” option means that when the running-config is saved to the startup-config a copy will also be saved on the tftp server, thus backing up the startup-config every time it’s changed.

In this example, we’ve configured the switch to save to the configuration file to the sw3725 sub-directory of a ttp server.
To test the setup, run the “write memory” command.

R1#enable
R1#write memory
or
R1#copy running-config startup-config

Looking on the sw3725 on the tftp server, we see a configuration file was uploaded:

sw3725.cfg-1

if you save the running-config a couple more times you wil get something like this:

sw3725.cfg-1
sw3725.cfg-2
sw3725.cfg-3

like you see the number at the end of the file name is incremented, every time you save the running-config

Based On: http://www.rainingpackets.com/configuring-cisco-ios-automatically-save-running-configuration-tftp-server-save

More Info at:

• http://www.cisco.com/c/en/us/td/docs/ios/fundamentals/configuration/guide/15_1s/cf_15_1s_book/cf_config-logger.html
• http://blog.ipspace.net/2006/11/log-configuration-commands-entered-on.html

Linux Switch (aka Bridge)

In this post Im going to show you how to configure a bridge (switch) in Linux. Here I will present several variations tha I have tested. The base cenário is the following:

# Set the eth1 IP address on the Rigth Laptop

ifconfig eth1 10.0.0.1 netmask 255.0.0.0

# Set the eth1 IP address on the Left Laptop

ifconfig eth1 10.0.0.2 netmask 255.0.0.0

Cenário 1 – No IPs on the Server NICs and Bridge

Server Configuration

# Load the bridge kernel module
modprobe bridge

# Activate eth1 and eth2 interface
ifconfig eth1 up

ifconfig eth2 up

# Create the bridge (virtual interface)
brctl addbr br0

# Add members to the bridge

brctl addif br0 eth1
brctl addif br0 eth2

Cenário 2 – No IPs on the Server NICs

Server Configuration

# Load the bridge kernel module
modprobe bridge

# Activate eth1 and eth2 interface
ifconfig eth1 up

ifconfig eth2 up

# Create the bridge (virtual interface)
brctl addbr br0

# Add members to the bridge
brctl addif br0 eth1
brctl addif br0 eth2

# Set the bridge IP address:
ifconfig br0 10.0.0.3 netmask 255.0.0.0

Now both computers are on the same LAN and can ping each other and the bridge interface, but can’t ping with the server NICs. This is like a switch with management ip.

Cenário 3 – IPs on the Server NICs and Bridge

Server Configuration

# Load the bridge kernel module
modprobe bridge

# Activate eth1 and eth2 interface
ifconfig eth1 up

ifconfig eth2 up

# Create the bridge (virtual interface)
brctl addbr br0

# Add members to the bridge
brctl addif br0 eth1
brctl addif br0 eth2

# Set the bridge IP address:
ifconfig br0 10.0.0.3 netmask 255.0.0.0

# Set the bridge IP address:
ifconfig br0 10.0.0.3 netmask 255.0.0.0

# Set the eth1 and eth2 IP address:
ifconfig eth1 10.0.0.4 netmask 255.0.0.0

ifconfig eth2 10.0.0.5 netmask 255.0.0.0

Now both computers are on the same LAN and can ping each other, the bridge interface, and also ping with the server NICs. It's like no switch I have ever seen.

Based On: http://openmaniak.com/openvpn_bridging.php