Networking Blog

IP routing/forwarding is disabled per default in Debian.
For enabling on the fly, you only have to write “1″ in /proc/sys/net/ipv4/ip_forward or to set the kernel parameter net.ipv4.ip_forward to “1″.

Method #1:
echo 1 > /proc/sys/net/ipv4/ip_forward
Method #2:
sysctl -w net.ipv4.ip_forward=1

The actual setting can be checked as following:

debian:~# sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1
debian:~# cat /proc/sys/net/ipv4/ip_forward
1
debian:~#

If you want permanent setting, the most [...]

I often use the feature interface-range on Cisco switches running IOS.
Not so long ago, i discovered the command interface-range macro, from which i never heard before.
With this macro, you can group several interfaces together and address them by a significant name.
Short example:

define interface-range UPLINKS FastEthernet0/1, FastEthernet0/24
define interface-range USERPORTS FastEthernet0/2 - 23

Usage:

switch#conf t
switch(config)#interface range macro USERPORTS
switch(config-if-range)#switchport [...]

To create a network interface without an IP address at all use the manual method and use pre-up and post-down commands to bring the interface up and down.
This can be necessary, when you like to bridge a VMWare VM to this interface or when it’s connected to a mirror port on the switch for sniffing [...]

Recently i stumbled across a nice feature in Cisco IOS for building customized menus.
The “menu”-command is really old and was introduced in IOS 10.0
You can i.e. use it for building a menu for CLI-unexperienced staff to simplify troubleshooting.
First of all, you have to configure a little bit AAA  as well as create a user with [...]