[RHEL 8/9] NetworkManager를 사용할 때 IP변경 주의 사항

RHEL 8, 9에서는 /etc/sysconfig/network-scripts/ifcfg-X 파일에 수정후에 IP가 반영되기는 하나 기존의 IP가 남아 있는 상황이 있을 수 있다. 

이런경우에는 connection을 down 했다가 다시 up해주면 기존 ip를 삭제 할 수 있다. 

### 1. IP 확인
[root@ip-10-0-1-244 ~]# ip -f inet -o addr
1: lo    inet 127.0.0.1/8 scope host lo\       valid_lft forever preferred_lft forever
2: eth0    inet 10.0.1.244/24 brd 10.0.1.255 scope global noprefixroute eth0\       valid_lft forever preferred_lft forever
3: eth1    inet 10.0.3.18/24 brd 10.0.3.255 scope global noprefixroute eth1\       valid_lft forever preferred_lft forever

### 2. IP수정
### eth1 10.0.3.18 -> 10.0.3.20
[root@ip-10-0-1-244 ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth1
 12L, 226C written
[root@ip-10-0-1-244 ~]# cat  /etc/sysconfig/network-scripts/ifcfg-eth1
# Created by cloud-init on instance boot automatically, do not edit.
#
BOOTPROTO=none
DEVICE=eth1
NAME=eth1
#HWADDR=02:cf:6a:07:2c:85
ONBOOT=yes
TYPE=Ethernet
USERCTL=no
IPADDR=10.0.3.20
NETMASK=255.255.255.0
GATEWAY=10.0.3.1

### 3. 서비스 재기동 
[root@ip-10-0-1-244 ~]# systemctl restart NetworkManager

### 4. 서비스 재기동 후에 기존의 IP가 남아있음을 확인
[root@ip-10-0-1-244 ~]# ip -f inet -o addr
1: lo    inet 127.0.0.1/8 scope host lo\       valid_lft forever preferred_lft forever
2: eth0    inet 10.0.1.244/24 brd 10.0.1.255 scope global noprefixroute eth0\       valid_lft forever preferred_lft forever
3: eth1    inet 10.0.3.18/24 brd 10.0.3.255 scope global noprefixroute eth1\       valid_lft forever preferred_lft forever
3: eth1    inet 10.0.3.20/24 brd 10.0.3.255 scope global secondary noprefixroute eth1\       valid_lft forever preferred_lft forever

### 5. nmcli에서의 설정정보인 connection을 down 했다가 다시 올려준다. 
[root@ip-10-0-1-244 ~]# nmcli con down eth1 
Connection 'eth1' successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)
### 내려감 
[root@ip-10-0-1-244 ~]# ip -f inet -o addr
1: lo    inet 127.0.0.1/8 scope host lo\       valid_lft forever preferred_lft forever
2: eth0    inet 10.0.1.244/24 brd 10.0.1.255 scope global noprefixroute eth0\       valid_lft forever preferred_lft forever

[root@ip-10-0-1-244 ~]# nmcli con up eth1 
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/3)

### 6. 최종확인 기존의 IP가 삭제 된것을 확인 할 수 있다. 
[root@ip-10-0-1-244 ~]# ip -f inet -o addr
1: lo    inet 127.0.0.1/8 scope host lo\       valid_lft forever preferred_lft forever
2: eth0    inet 10.0.1.244/24 brd 10.0.1.255 scope global noprefixroute eth0\       valid_lft forever preferred_lft forever
3: eth1    inet 10.0.3.20/24 brd 10.0.3.255 scope global noprefixroute eth1\       valid_lft forever preferred_lft forever