[SOLVED] What is difference in ip and ifconfig command when usage is for adding alias.?

bhushanj_a1 · 12-26-2011, 08:46 AM

Hello,

What is the difference in the execution of below two commands??

1. ifconfig eth1:1 10.0.0.2/24 broadcast 10.0.0.255
On success, one can see the alias getting added to the list of interfaces. Checked by ifconfig

2. ip addr add 10.0.0.2/24 broadcast 10.0.0.255 dev eth1
On success, one can not see the alias getting added in the list of the interfaces. But, returns 0 and on failure returns 2.

Does any one know how the working differ?

zhjim · 12-27-2011, 07:50 AM

Quote:

Originally Posted by bhushanj_a1

2. ip addr add 10.0.0.2/24 broadcast 10.0.0.255 dev eth1
On success, one can not see the alias getting added in the list of the interfaces. But, returns 0 and on failure returns 2.

Try this command

Code:

ip addr add 10.0.0.2/24 broadcast 10.0.0.255 label eth1:1 dev eth1

With it the pseudo interface will also show up with the ifconfig command

I guess the both commands work similar when setting up the interface, but differ in the way they list them. I can't find the associated /proc entry to see how the two tools differ in their display format.

What I'm thinking about right now if the names of the interace have any further meaning beside just beeing names. Don't know if a command like iptables -A INPUT -i eth1:1 would work...

bhushanj_a1 · 12-28-2011, 12:04 AM

Thanks zhjim for you inputs.

Addition of label eth1:1 is correct but without label system does makes an entry. Only the mystery is where that can be found.

zhjim · 12-28-2011, 07:46 AM

I looked up the source code of the ifconfig command (Can be found here http://sourceforge.net/projects/net-tools/) but to no avail. Seems like it opens a socket and gets the infos from there. But I don't understand how it is done.