How does each extra IPv4 stay on the NIC after reboot?

Each console line is one address

Once the machine is paid and connectable, the console splits the addresses, drops duplicates, and lists them in a scrolling box. The first line is shown on its own. SSH or RDP uses that line only. Every later line is also one complete IPv4. The list has no network address, no broadcast address, and no leftover hosts to calculate.

The order already includes 1 IPv4. Further addresses are added one by one at $1.6 each per month, up to 255 more, and the included address plus the extras stay within 256. The number of lines should equal that total. Four extra addresses mean five lines, not a prefix written as /29.

The addresses below are documentation examples. Replace them with the lines from the console. Suppose the first line is 203.0.113.10 and the other two are 203.0.113.21 and 203.0.113.34. The three lines are not contiguous. A gap does not turn them into a block, and the numbers in between are not on this machine.

Copy the whole list before editing the NIC. Check the count and each line against that copy. Do not derive missing addresses from a mask. An address that is not on the list does not go on the NIC.

Keep the first prefix; extras use a host mask

After installation the first address is already on the NIC, with the prefix length and default gateway from that install. Leave all three as they are. The prefix may be /24 or some other length. Read it from the system. Do not replace it with a mask derived from how many addresses were bought.

A /29 always occupies eight addresses: one network address, six host addresses, and one broadcast address. Buying addresses one by one does not deliver those eight positions, and it does not promise that the lines sit next to each other. A mask of 255.255.255.248 makes the host treat neighbouring numbers as on-link. Those neighbours are not part of this order.

Each extra line uses 255.255.255.255, which is /32. The NIC then recognises that one host address and does not claim the numbers beside it. The default gateway stays the original one. Do not add a second default route for a new address.

When the lines happen to be consecutive, still append them one by one, still with /32. Consecutive numbers only mean the integers sit together. They do not mean this machine received a subnet.

Add them on the NIC that already has the first address

Extra addresses do not come with a second NIC. Find the interface that already holds the first address, and add the new lines there.

ip -4 addr show
ip route show default

In the first command, the interface that contains the first console line is the one to edit. Later examples call it eno1. The real name may be eno1, eth0, or vmbr0. In the second command, the address after via is the current gateway, and the device after dev should be that same interface. Copy both from this output. Do not invent a gateway from a new address.

Proxmox VE 8 or 9 often places the first address on the bridge vmbr0, while the physical port is only a bridge member. Follow the first address. If it already lives on the bridge, adding the new line to the physical port usually means the new address does not answer.

When a site runs inside a virtual machine, the address belongs on the virtual NIC that answers it. The host should not also hold the same line. The same line on both the bridge and the guest is answered by whichever side responds first. Inside the guest the rule is the same: leave the original address and gateway, and add the new line as /32.

Add the address once as a temporary check, confirm the line is visible, then write the boot configuration. A temporary add disappears on reboot. It only checks that the interface is the right one.

ip addr add 203.0.113.21/32 dev eno1
ip -4 addr show dev eno1

The output should show the original first line and the new line together. The prefix on the first line should be unchanged, and the default route should still point at the original gateway. Repeat the temporary add for 203.0.113.34, then write the file.

Write the file the boot process reads

Edit only the file that already contains the first address. Do not leave a second file that defines the same interface with only the new addresses. When both apply, the one read later can drop the first line. SSH would then be left on an extra address, and it would no longer match the command in the console.

Ubuntu Server 22.04, 24.04, and 26.04 use netplan. Open the yaml that already has the first line. Keep that line under addresses and append the /32 lines. Leave the default route and the nameserver lines as they are.

network:
  version: 2
  ethernets:
    eno1:
      addresses:
        - 203.0.113.10/24
        - 203.0.113.21/32
        - 203.0.113.34/32
      routes:
        - to: default
          via: 203.0.113.1

The /24 and 203.0.113.1 in the example mean “keep the original values”. If the machine uses another prefix or gateway, copy them from the ip output. If the file already has other keys, append address lines only. Do not replace the whole file with the snippet above.

After saving, run netplan try. It applies the configuration and rolls back when the timer expires. During that window, open a second SSH session to the first address and confirm it still connects. Run netplan apply only after try succeeds. Applying an unchecked file from the only open session leaves no way back in if that session drops.

Debian, Proxmox, and NetworkManager

On Debian 11, 12, or 13, if the address is in /etc/network/interfaces, edit that file. Append with post-up and remove with pre-down when the interface goes down. Leave the original address and gateway lines as the installer wrote them.

auto eno1
iface eno1 inet static
    address 203.0.113.10/24
    gateway 203.0.113.1
    post-up ip addr add 203.0.113.21/32 dev eno1
    post-up ip addr add 203.0.113.34/32 dev eno1
    pre-down ip addr del 203.0.113.21/32 dev eno1
    pre-down ip addr del 203.0.113.34/32 dev eno1

A Proxmox bridge lives in the same file. Use vmbr0 when that bridge already holds the first line. Do not turn the physical port’s bridge stanza into an address stanza.

AlmaLinux 8, 9, and 10, and CentOS Stream 9 and 10, are usually managed by NetworkManager. Read the connection name from nmcli connection show. Append addresses on that connection. Leave ipv4.gateway as it is, and do not change the method to a value that clears addresses.

nmcli connection modify "System eno1" +ipv4.addresses 203.0.113.21/32
nmcli connection modify "System eno1" +ipv4.addresses 203.0.113.34/32
nmcli connection up "System eno1"

modify writes the connection profile, so the lines survive reboot. ip addr add alone lasts only until the next boot. After up, ip -4 addr should still show the first line.

FreeBSD 13 stores aliases in /etc/rc.conf. Copy the interface name from the ifconfig block that already shows the first address.

ifconfig_em0_alias0="inet 203.0.113.21 netmask 255.255.255.255"
ifconfig_em0_alias1="inet 203.0.113.34 netmask 255.255.255.255"

The existing ifconfig_em0 line keeps the first address and the default route. If alias0 is already taken, use the next free number. Do not invent a second NIC for the aliases.

One machine should keep one network manager for this interface. If interfaces, netplan, and NetworkManager all define it, boot order decides which address set remains. Edit the file that already contains the first line, and leave the others alone.

On Windows, add the address and leave the gateway empty

With Windows Server, access is RDP, still using only the first console line. Add extra addresses on the adapter that already holds that line. Standard adds $18.1 a month and Datacenter adds $31.8, for 2019, 2022, or 2025. The system price is separate from the address count. Addresses are still sold one by one.

Open the IPv4 properties of that adapter, then Advanced, and add a row in the address list. Put the extra console line in the address field and 255.255.255.255 in the mask. Leave the gateway on the new row empty. Keep the gateway that is already there. A second gateway competes with the original default route.

In PowerShell, take the interface alias from Get-NetAdapter. With SkipAsSource set to true, the new address can accept inbound traffic, while new outbound connections still leave from the first address. Whether sites share that first line or each take their own is covered in sharing one address or giving each site its own.

New-NetIPAddress -InterfaceAlias "Ethernet" -IPAddress 203.0.113.21 -PrefixLength 32 -SkipAsSource $true
New-NetIPAddress -InterfaceAlias "Ethernet" -IPAddress 203.0.113.34 -PrefixLength 32 -SkipAsSource $true

The command writes system configuration. It is not a one-shot that vanishes. Get-NetIPAddress should list the new rows with prefix length 32. The original prefix and default route stay as they were.

Check the list after reboot

1. 01 Reboot the machine. Restarting only the network service is not the check. Temporary addresses disappear here. Addresses in the boot configuration come back.
2. 02 Run ip -4 addr again, or open the adapter address list on Windows. The first line is still there, with the same prefix as before the reboot.
3. 03 There is one default route, and its next hop is still the original gateway. On Linux, check via in ip route show default.
4. 04 Tick the console list line by line. Every listed line is on the NIC, and the NIC has no address that is absent from the list.
5. 05 From another machine, open SSH or RDP to the first address. Confirm that management path before testing a service port on an extra address.

A count command can help once. The conclusion still follows the list. The next command counts global IPv4 addresses. The number should equal the included address plus the extras purchased.

ip -4 -o addr show scope global | wc -l

If a line is missing, go back to the boot file and see whether that line was never written, or was written into a file the boot process does not read. If there is an extra line, remove any address that is not on the list, especially a network or broadcast address calculated from a /29.

An address can be on the NIC while a service port is still dropped by the firewall. If ufw, firewalld, or Windows Firewall does not allow 80, 443, or the port the service actually uses, the connection times out. That is port policy. It comes after confirming the line is still present following a reboot.

When the count is short, add extra IPv4 on the configure page at $1.6 each per month, inside the same monthly rent. The 128GB tier is $454.8 a month and the 256GB tier is $612.7. Memory is DDR4-3200 ECC RDIMM and cannot be added later. The processor is an AMD EPYC 7543P, 32 cores and 64 threads, 2.8 to 3.7 GHz. The default disks are two 1TB NVMe drives, with no hardware RAID, each attached directly, and usable capacity is the sum of both, about 2TB. Bandwidth starts at 250 Mbps and is unmetered. 1 Gbps adds $245.0 a month and 2 Gbps adds $742.7. Monthly rent is the sum of those items. The amount due is monthly rent times the number of months. Monthly, quarterly, semiannual, and annual terms have no discount and no setup fee. The machine is deployed in Tokyo, Japan.

This note only answers whether each line is present and whether it is still present after reboot. Whether several sites share the first line or each take a line, and why a newly opened connection still leaves from the first line, is the next note.