Question : eth1:0

hi

eht0 and eht1 physical interface

but whatis  eth1:0  
and how to create it (like eth1:0 )

Thanks

Answer : eth1:0

Hi,



Eth1:0 is a Logical interface, virtual aliases Or label for a particular address rather than a device name.

virtual aliases are not the same as Logical IP addresses, with regards to the fact that you can't remove a Virtual Alias on the fly. And in our environment that is essential. That creating a logical IP address on an interface that starts with 0 (ie eth1:0) and then creating multiple logical IP addresses below that... (ie eth1:1, eth1:2, eth1:3, eth1:4....) if you remove eth1:0, you will remove them all (which is very bad), however, if you remove eth1:0 or any of the others Logical IP addresses, it will only remove that specific ip address (which is desired). I was able to save my logical IP address information by creating a custom startup script and calling the following commands:

ifconfig eth0:2 10.251.13.49
route add -host 10.251.13.49 dev eth0:2

It is also VERY important that you execute the following command: route add -host dev (ex. route add -host 10.251.13.44 dev eth0:1) If you dont do that, it will erase if any of the other IP addresses are erased.

Some other article :

What is Logical interface?
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/inter_c/icdlogin.htm
http://www.shorewall.net/Shorewall_and_Aliased_Interfaces.html