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netshade
Tux's lil' helper
Joined: 02 Jan 2004
Posts: 90
Location: Sweden
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 Posted: Wed Jan 15, 2025 2:10 pm Post subject: Help finding reason for dropped IP address. |
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So, this is most (definitvely) likely my fault and I can't blame anything but my own screwed up mind. However, I can't un-screw it enough to figure out how and why this happens.
I run a Gentoo vm on a proxmox host (among a lot of other stuff) and for some very odd reason every now and then the vm disconnects from the lan.
When I log on the console and look there's no IPv4-address assigned to ens18 which is the default NIC. Doing | Code: | | ip link set ens18 down |
followed by | Code: | | ip link set ens18 up |
twice resolves it and it comes back online with the same IP as I reserved for it in the router.
I can't figure out which journal I should look in or how to find the lines regarding something that might have happened several hours ago. My "only" somewhat feasible theory is that there's something happening with the docker nic's which somehow effects ens18 as well but that's just a hunch based on the fact that I can see a bunch of interfaces going up and down in the logs, but I am too confused to make sense of it.
The bits I can eliminate:
The host. All other vm's are stable in that sense so unless something very weird is going on that's not it.
The network. Same thing here. I have several hosts with reserved IP's which doesn't do this so it's unlikely.
Other than that I'm stumped and if someone has any thoughts please share them. I am an amateur, self thought and I do lack several important chapters in the book of knowledge. This is one of them. (Also, if some kind of output or logs would help just let me know. This is annoying me but for some reason I can't seem to focus enough to figure it out...)
Regards, NetShade. Gentoo-victim since 2003 and happily FUBAR'D by ADHD.[/code]
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From where the shadows turn into nightmare, netshade greets you... |
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druggo
Guru
Joined: 24 Sep 2003
Posts: 325
Location: Hangzhou
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| Posted: Sat Jan 18, 2025 3:41 pm Post subject: |
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I once encountered a situation in Ubuntu where the network card's IP address was lost. I found out it was due to a DHCP issue—the IP lease expired and failed to renew, causing the IP to be lost. At the time, I simply set the IP to a static address to resolve the issue.
You might want to check the network-related in the syslog, as there could be some clues there.
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netshade
Tux's lil' helper
Joined: 02 Jan 2004
Posts: 90
Location: Sweden
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| Posted: Sun Jan 19, 2025 11:05 am Post subject: |
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| druggo wrote: | I once encountered a situation in Ubuntu where the network card's IP address was lost. I found out it was due to a DHCP issue—the IP lease expired and failed to renew, causing the IP to be lost. At the time, I simply set the IP to a static address to resolve the issue.
You might want to check the network-related in the syslog, as there could be some clues there. |
Thanks, that makes sense and I'll dig into that.
Like I mentioned, I probably did wrap my brain the wrong way around this so any tips are appreciated! =)
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From where the shadows turn into nightmare, netshade greets you... |
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Ralphred
l33t
Joined: 31 Dec 2013
Posts: 709
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| Posted: Sun Jan 19, 2025 4:52 pm Post subject: |
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| druggo wrote: | | I found out it was due to a DHCP issue—the IP lease expired and failed to renew, causing the IP to be lost. |
I've had similar where an overly restrictive firewall was allowing the "give me a lease please?" traffic but not the "the lease has half expired, can I renew it please?" traffic, so the IP dropped every <lease time> for a bit while the dhcp client sorted it's life out. A good test would be to drop the lease time, just for the problem machine, to a few minutes and then see if it breaks more frequently, or fails a graphical ping test every <lease time> when it expires and has to be negotiated from scratch. Or just switch it to static and see if that "fixes" the problem. |
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