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I am working to establish a CentOS-8 machine in a hosted cloud environment as part of an effort to migrate the operations of my company off local machines. I need to add 2 alias IP address to the interface defined by this script.

[root@XXXXXXXX network-scripts]# cat ifcfg-ens192
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=ens192
UUID=e10ccada-6834-4f7f-b415-78e2d0b61e76
DEVICE=ens192
ONBOOT=yes
IPADDR=10.1.0.25
PREFIX=24
GATEWAY=10.1.0.1
DNS1=66.129.64.228
IPV6_PRIVACY=no
DNS2=66.129.96.228
[root@XXXXXXXX network-scripts]#

After editing, I have this.

[root@XXXXXXXX network-scripts]# cat ifcfg-ens192
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=ens192
UUID=e10ccada-6834-4f7f-b415-78e2d0b61e76
DEVICE=ens192
ONBOOT=yes
IPADDR0=10.1.0.25
IPADDR1=10.1.0.20
IPADDR2=10.1.0.76
PREFIX=24
GATEWAY=10.1.0.1
DNS1=66.129.64.228
IPV6_PRIVACY=no
DNS2=66.129.96.228
[root@XXXXXXXX network-scripts]#

After restarting the machine I discover that DNS is not working.

[root@XXXXXXXX network-scripts]# ping google.com
ping: google.com: Name or service not known
[root@XXXXXXXX network-scripts]# ping 66.129.64.228
connect: Network is unreachable
[root@XXXXXXXX network-scripts]# ping 66.129.96.228
connect: Network is unreachable
[root@XXXXXXXX network-scripts]#

and ip addr display the following.

[root@XXXXXXXX network-scripts]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:50:56:af:4f:5c brd ff:ff:ff:ff:ff:ff
    inet 10.1.0.25/8 brd 10.255.255.255 scope global noprefixroute ens192
       valid_lft forever preferred_lft forever
    inet 10.1.0.20/8 brd 10.255.255.255 scope global secondary noprefixroute ens192
       valid_lft forever preferred_lft forever
    inet 10.1.0.76/8 brd 10.255.255.255 scope global secondary noprefixroute ens192
       valid_lft forever preferred_lft forever
    inet6 fe80::6a22:319:a718:3d5b/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 52:54:00:7f:16:df brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
       valid_lft forever preferred_lft forever
4: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc fq_codel master virbr0 state DOWN group default qlen 1000
    link/ether 52:54:00:7f:16:df brd ff:ff:ff:ff:ff:ff
[root@XXXXXXXX network-scripts]#

It looks like this is not really a DNS issue, but a ifcfg script issue and I don't know how to correct the script.

ZZR3556
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  • The netmasks are not correct in the `ip addr` output. They show as /8 instead of /24. Try adding `PREFIX0=24`, `PREFIX1=24` and `PREFIX2=24` lines to ifcfg-ens192 – Brandon Xavier Apr 09 '21 at 16:29
  • I already tried adding PREFIX# for each ADDR#. This looked like the obvious thing to do, but did not work. – ZZR3556 Apr 09 '21 at 17:48
  • Actually, yes, that almost exactly right. But for ADDR0 and PREFIX0 the index digit needs to be dropped. – ZZR3556 Apr 09 '21 at 18:10

1 Answers1

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First change IPADDR0 back to IPADDR. Then add PREFIX1=24 and PREFIX2=24.

Better yet, revert to the original version of the file (ifcfg_ens192) and then use the NetworkManager Text UI configuration tool (nmtui) to achieve the same result.

ZZR3556
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