Network on blog.iankulin.com

Allowing Proxmox to use a Dynamic IP

Thu, 06 Apr 2023 00:00:00 +0000

I’ve discussed before, that when you first install Proxmox, it grabs an IP address from your DHCP server (this usually runs in your ISP modem if you haven’t created a better setup), but then it stores it as a static ip. This is a sort of compromise that makes sense and works for most circumstances.

As soon as I’ve provisioned a new Proxmox server, I then usually tell the DHCP server, to always serve that address to the MAC address of the new Proxmox server. Since Proxmox does not use the DHCP server on subsequent boots, all that really does is prevent the DHCP server give the same IP address out to another device - which had happened to me prompting the earlier post. The DHCP server had given the address to a wifi lightbulb while the server was off, then when the Proxmox server booted up, the netwrok access was all messed up.

In general, servers should have a static IP address - they are providing resources that other devices on the network need to access, so the combination of grabbing a DHCP address, using it statically, then me locking it in at the DHCP server makes sense.

Except that I’m building a system with a couple of VM’s and a NAS that I’m going to post off, and have it set up by a non-techie at a remote site. So I really need Proxmox on that machine to look for a DHCP server when it boots and collect a dynamic IP address. Like a lot of things in Linux, this is quite a simple change if you know where to look.

What to Change

The configuration file for the network interfaces is /etc/network/interfaces the one on the Proxmox machine I’m setting up looked like this:

iface lo inet loopback

iface eno1 inet manual

auto vmbr0
iface vmbr0 inet static
	address 192.168.100.30/24
	gateway 192.168.100.1
	bridge-ports eno1
	bridge-stp off
	bridge-fd 0

iface is short for interface, and is followed by the interface name. These are the same names you see when you type in ip addr to see the IP addresses.

So this is the bit we are interested in:

iface vmbr0 inet static
	address 192.168.100.30/24
	gateway 192.168.100.1
	bridge-ports eno1
	bridge-stp off
	bridge-fd 0

All that bridge stuff can stay the same, I’ll comment out the static bits and change it to use the DHCP. The final file looks like:

auto lo
iface lo inet loopback

iface eno1 inet manual

auto vmbr0
#iface vmbr0 inet static
#	address 192.168.100.30/24
#	gateway 192.168.100.1
iface vmbr0 inet dhcp
	bridge-ports eno1
	bridge-stp off
	bridge-fd 0

I used the mac address to tell the DCHP server to allocate it a different address, and rebooted and Proxmox picked up the new address perfectly.

Hosts

Now the server had a new address, there’s one more place I need to update; /etc/hosts contains the domain information you set during the Proxmox install, and it will include that old IP address. Once the system has a new one, it needs to be edited to include that.

127.0.0.1 localhost.localdomain localhost
192.168.100.28 pve-kr01.local pve-kr01

# The following lines are desirable for IPv6 capable hosts

::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

After the system is installed at the remote site and booted up, I’ll ssh in (with Tailscale) and make that change, and hopefully be able to access the DHCP server so it does not change in future.

Resources

I found these posts useful when figuring this out:

Versions: Proxmox 7.4-3

No DNS on Proxmox machine

Fri, 17 Mar 2023 00:00:00 +0000

I had some more network weirdness setting up this new Proxmox machine. When I went to run the updates it couldn’t resolve any of the addresses:

root@pve-kr01:~# apt update
Err:1 http://ftp.au.debian.org/debian bullseye InRelease
 Temporary failure resolving 'ftp.au.debian.org'
Err:2 http://download.proxmox.com/debian/pve bullseye InRelease
 Temporary failure resolving 'download.proxmox.com'
Err:3 http://security.debian.org bullseye-security InRelease
 Temporary failure resolving 'security.debian.org'
Err:4 https://enterprise.proxmox.com/debian/pve bullseye InRelease
 Temporary failure resolving 'enterprise.proxmox.com'
Err:5 http://ftp.au.debian.org/debian bullseye-updates InRelease
 Temporary failure resolving 'ftp.au.debian.org'
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://ftp.au.debian.org/debian/dists/bullseye/InRelease Temporary failure resolving 'ftp.au.debian.org'
W: Failed to fetch http://ftp.au.debian.org/debian/dists/bullseye-updates/InRelease Temporary failure resolving 'ftp.au.debian.org'
W: Failed to fetch http://download.proxmox.com/debian/pve/dists/bullseye/InRelease Temporary failure resolving 'download.proxmox.com'
W: Failed to fetch http://security.debian.org/dists/bullseye-security/InRelease Temporary failure resolving 'security.debian.org'
W: Failed to fetch https://enterprise.proxmox.com/debian/pve/dists/bullseye/InRelease Temporary failure resolving 'enterprise.proxmox.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.

So some sort of DNS problem. The entry for the DNS is in /etc/resolv.conf when I looked in there, it said:

search local
nameserver 127.0.0.1

Well, that does not seem great. I feel like it should be pointing at the DNS in my router, or even upstream at my ISP or google’s DNS server. Before I dive in and start editing, I thought I’d check my other servers. The first one has clearly been altered as part of installing TailScale, so that wasn’t much help, but on the dev machine it said:

search local
nameserver 192.168.100.1

Which is more like what I was expecting, that’s the address given out by my DHCP server for DNS. I could just edit the new machine to this, but since this is the third lot of network related weirdness related to this install (the second was that my managed switch’s web interface was down, and I couldn’t ping it, but it was still passing traffic, again), and the first, discussed in yesterday’s post, was that DHCP had provided a dynamic address that was already assigned to another device.

I swapped out the network cable, and noticed the port lights flashing. Perhaps there is a broken pair in the other cable? It was odd that it was working sort of.

I reinstalled Proxmox from scratch, and carefully watched the console messages and checked all the network settings (it correctly picked up the reserved address and correct DNS server). Then everything worked.

Proxmox Dynamic IP

Thu, 16 Mar 2023 00:00:00 +0000

I ran into a little hiccup today. I’m building out a Jellyfin media server in a little HP G2 Mini PC. The config was going to be a Debian server inside Proxmox (because I love VM snapshots for backups) running Jellyfin in a container. There’ll be an external USB3 hard drive for the media storage.

I was intending to build it all out and test it, then ship it to it’s final home.

I’ve probably installed Proxmox five or six times by now since I’m always playing around with my test machine, and never really thought about the screen that comes up during the install showing the network details it’s picked up from DHCP.

Today once I’d finished installing Proxmox, I couldn’t SSH into it

I knew I had the right IP address since it shows that on the console at the end of the boot process. Looking in my router, it said 192.168.100.2 was connected, but by wifi on the SSID I use for IOT devices.

That ESP device name is a giveaway - it’s one of my wifi light bulbs. A quick ip addr on the new Proxmox via the console shows it is convinced that it is 192.168.100.2 I can ping 8.8.8.8 from it, but DNS is not working. My conclusion is that I’ve got two devices with the same IP on my network.

I’m not sure how this came about. The network cable I was using is an old CAT5 with the clips broken off both ends I use for fiddling around, so perhaps there was a dodgy connection right at a crucial moment? It seems odd. usually when I encounter the ’two machines with the same IP’ problem, I’ve caused it somehow.

No problem I thought, now I’ve got the MAC address from the Proxmox machine, I’ll just reserve an available IP address for it. I did that, and rebooted Proxmox, but it was still on the old address. Then I remembered that question during the install process - it must collect an address from DHCP, then after the users has committed to it, write it into /etc/hosts and /etc/network/interfaces I reinstalled Proxmox, it picked up the new address and I saved it as the static IP.

That’s not really problem solved though - I’m sending this off to a network where I don’t know the network configuration. I was hoping just to let it pick up a DHCP address that would remain somewhat stable since the machine is going to be on 24/7.

It’s not unreasonable for Proxmox to expect a VM host machine is going to have a static IP address, but it’s inconvenient for this situation. I’ll have to discover how to make it dynamic (probably by editing those two files). I’ll have Tailscale on it, so I can remote in afterwards to make it static, although without also reserving it in their router that carries a small risk too.

Netgear GS108E switch problem

Tue, 14 Feb 2023 00:00:00 +0000

I had a weird issue today that I wouldn’t have known about if I didn’t have an over-engineered home network monitoring system.

I’ve got a new GS108E managed switch, purchased in anticipation of connecting a NAS to the homelab - I want to have a solid 1Gb connection between the NAS and the servers, and also in anticipation of moving to VLANs before I start to expose self-hosted services to the internet.

It sat plugged into the network for 24 hours with no load, then I moved the server over on to it. I hadn’t changed any configuration on it (it comes out of the box just configured as a switch). It’s IP address was set by DHCP, and I’d reserved that in my Netgear modem.

It was all working perfectly, then a day later, it suddenly stopped responding to pings and the interface was unavailable. The weird bit was that the network was still working perfectly - I could ssh to the server through it, but it didn’t appear on the network. The leds on the connected ports where flashing away happily.

There are a couple of search results for this switch working, but the interface not reachable - but they all seem to involve complicated VLAN setups where people have locked themselves out rather than the default config suddenly having an issue.

It will be disappointing if this is going to be a regular issue, but at least I’ll have good data to investigate it!