Using the ip command to change IP address

ohlookpie · 06-23-2012, 03:25 PM

If I do an "ifconfig <iface> <IP>" it changes the IP address for my device. If I do an "ip addr change dev <iface> <IP/mask>" it adds a secondary IP to device (same happens with an "ip addr add dev <iface> <IP/mask>"). So, how do I actually change the IP address associated with then interface using the ip command?

Code:

[root@money ~]# ip addr show dev eth1
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 52:54:00:ca:49:04 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.100/24 brd 192.168.122.255 scope global eth1
    inet6 fe80::5054:ff:feca:4904/64 scope link 
       valid_lft forever preferred_lft forever
[root@money ~]# ifconfig eth1 192.168.122.105
[root@money ~]# ip addr show dev eth1
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 52:54:00:ca:49:04 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.105/24 brd 192.168.122.255 scope global eth1
    inet6 fe80::5054:ff:feca:4904/64 scope link 
       valid_lft forever preferred_lft forever
[root@money ~]# ip addr change dev eth1 192.168.122.102/24
[root@money ~]# ip addr show dev eth1
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 52:54:00:ca:49:04 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.105/24 brd 192.168.122.255 scope global eth1
    inet 192.168.122.102/24 scope global secondary eth1
    inet6 fe80::5054:ff:feca:4904/64 scope link 
       valid_lft forever preferred_lft forever

jefro · 06-23-2012, 05:32 PM

"ip addr change dev eth1 192.168.122.102/24" Seems odd to me to use the change dev.

ip command is almost too much for anyone. Why they did it I don't know. http://linux.die.net/man/8/ip has the command way done in a confusing place. And it can't be searched by any web search either.

This is a more compact version. http://linux-ip.net/gl/ip-cref/node3.html

ohlookpie · 06-23-2012, 05:39 PM

Quote:

Originally Posted by jefro

"ip addr change dev eth1 192.168.122.102/24" Seems odd to me to use the change dev.

ip command is almost too much for anyone. Why they did it I don't know. http://linux.die.net/man/8/ip has the command way done in a confusing place. And it can't be searched by any web search either.

This is a more compact version. http://linux-ip.net/gl/ip-cref/node3.html

Exactly my issue: I could not search the web for the ip command and get any useful documentation. The ip command is preferred by Redhat over the ifconfig command for those doing the RHCSA/RHCE exams. However, I have tried many different things, and I can find no decent way of changing the IP address for a device. The only thing I have discovered is that if I either do an "ip del" and delete the primary IP address, or an "ip flush" and flush all settings, then I can change the IP; but this seems a ridiculous way of doing things.

cospengle · 06-23-2012, 06:25 PM

I'm not sure if there is a convenient way to change the address as you describe, but adding a new address and removing an old address doesn't seem rediculous to me.

If you had an interface with ten IP addresses how would you know which one you were changing? I think it's better to just add another and remove the one you don't want.