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What's the impact, if any, on having values greater than zero/forever for valid_lft and preferred_lft? Should I worry about this, and if so, how to set it automatically to forever at boot time (preferably using Netplan)?

root:~# ip a 2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether aa:00:11:22:33:44 brd ff:ff:ff:ff:ff:ff inet 111.111.111.111/32 scope global ens3 valid_lft 86154sec preferred_lft 86154sec inet 222.222.222.222/32 scope global ens3 valid_lft forever preferred_lft forever inet6 fe80::aaa:bbb:ccc:ddd/64 scope link valid_lft forever preferred_lft forever root:~# ip addr change 111.111.111.111 dev ens3 valid_lft forever preferred_lft forever root:~# ip a 2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether aa:00:11:22:33:44 brd ff:ff:ff:ff:ff:ff inet 111.111.111.111/32 scope global ens3 valid_lft forever preferred_lft forever inet 222.222.222.222/32 scope global ens3 valid_lft forever preferred_lft forever inet6 fe80::aaa:bbb:ccc:ddd/64 scope link valid_lft forever preferred_lft forever

I am asking this question because I realized that the server default IP address switched from 111.111.111.111 to 222.222.222.222 without manual interraction, i.e., ifconfig -a displayed this for ens3:

root:~# ifconfig -a ens3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 222.222.222.222 netmask 255.255.255.255 broadcast 0.0.0.0 inet6 fe80::aaa:bbb:ccc:ddd prefixlen 64 scopeid 0x20<link> ether aa:00:11:22:33:44 txqueuelen 1000 (Ethernet) RX packets 206473 bytes 54232020 (54.2 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 111121 bytes 19855468 (19.8 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 
root:~# cat /etc/netplan/*.yaml network: version: 2 ethernets: ens3: dhcp4: yes match: macaddress: aa:00:11:22:33:44 mtu: 1500 set-name: ens3 addresses: - 111.111.111.111/32 - 222.222.222.222/32 nameservers: addresses: - 8.8.8.8 - 4.4.4.4 - 1.1.1.1 - 1.0.0.1

Could valid_lft and preferred_lft be the reason of the switch?

If not, how to make sure that the main IP address remains 111.111.111.111 in this configuration? I'm using Virtualmin, and once in a while it flashes a message saying that the main IP addess has been changed to 222.222.222.222, and offers to modify it from 111.111.111.111 to 222.222.222.222. At the time, ifconfig displays 222.222.222.222 as shown above.

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  • Why are you trying to get one IP address via DHCP and one manually? Commented Aug 22, 2020 at 14:35
  • @MichaelHampton, this is the config given by the ISP, i.e., OVH. Each IP is added to the main NIC. I tried to (1) dhcp4:no and set addresses:111. & 222., (2) dhcp4:yes without addresses:, and (3) remove the match:macaddress:set-name entry set, but none of that works... I'm note sure what's happening on their end... Commented Aug 23, 2020 at 7:56
  • You can just configure all the addresses manually. OVH will not change them unless you add or delete one from your account. Commented Aug 23, 2020 at 13:52
  • Sure, I'd love that option, but how to do that with a single NIC using Netplan? Commented Aug 24, 2020 at 9:16

1 Answer 1

Reset to default
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I ended up writing a one-liner script that sets valid_lft and preferred_lft to forever, run as a service at boot time, after the network service.

I do not know if this is the solution to my problem, but since I've done that, the main IP doesn't switch automatically anymore.

/usr/sbin/ip addr change 111.111.111.111 dev ens3 valid_lft forever preferred_lft forever
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