[SOLVED] Proxmox Machine Mysteriously Lost Network Connectivity

M

Mog

New Member
Oct 7, 2021
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Hey folks. First post and I'm here because I'm at wits end.

Long story short, I was replacing a suspected bad HBA card with a new one and couldn't get it to show up as a device inside proxmox. After a bit of fiddling I finally got the machine to detect it, but network connectivity vanished. I spent a while troubleshooting (thought that the network interface must have changed, etc.) to no avail.

I've currently removed the HBA completely, so the only PCI device in the machine is the graphics card (no onboard graphics controller). I still have no network connectivity and can't figure out why. I've tried verifying and reverifying /etc/network/interfaces and it looks fine, but doesn't work.

When I try to ping the gateway:
Code: 
root@proxmox:~# ping 172.16.0.1
PING 172.16.0.1 (172.16.0.1) 56(84) bytes of data.
From 172.16.0.0 icmp_seq=1 Destination Host Unreachable
From 172.16.0.0 icmp_seq=2 Destination Host Unreachable
From 172.16.0.0 icmp_seq=5 Destination Host Unreachable
From 172.16.0.0 icmp_seq=6 Destination Host Unreachable
^C
--- 172.16.0.1 ping statistics ---
7 packets transmitted, 0 received, +4 errors, 100% packet loss, time 152ms

ip -a:
Code: 
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: enp5s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast master vmbr0 state DOWN group default qlen 1000
    link/ether b8:97:5a:09:75:46 brd ff:ff:ff:ff:ff:ff
5: veth100i0@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr100i0 state UP group default qlen 1000
    link/ether fe:5d:69:e8:61:87 brd ff:ff:ff:ff:ff:ff link-netnsid 0
6: fwbr100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 66:27:ba:14:bc:b3 brd ff:ff:ff:ff:ff:ff
7: fwpr100p0@fwln100i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 12:62:39:1e:f5:b2 brd ff:ff:ff:ff:ff:ff
8: fwln100i0@fwpr100p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr100i0 state UP group default qlen 1000
    link/ether 66:27:ba:14:bc:b3 brd ff:ff:ff:ff:ff:ff
10: veth104i0@if9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr104i0 state UP group default qlen 1000
    link/ether fe:06:9c:0e:53:ae brd ff:ff:ff:ff:ff:ff link-netnsid 1
11: fwbr104i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 8a:ae:75:98:f9:ab brd ff:ff:ff:ff:ff:ff
12: fwpr104p0@fwln104i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 06:a0:05:e3:1e:15 brd ff:ff:ff:ff:ff:ff
13: fwln104i0@fwpr104p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr104i0 state UP group default qlen 1000
    link/ether 8a:ae:75:98:f9:ab brd ff:ff:ff:ff:ff:ff
14: tap105i0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master fwbr105i0 state UNKNOWN group default qlen 1000
    link/ether 76:a9:0d:6a:4d:f0 brd ff:ff:ff:ff:ff:ff
15: fwbr105i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 5e:7e:de:38:ce:36 brd ff:ff:ff:ff:ff:ff
16: fwpr105p0@fwln105i0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 02:bb:16:12:a9:04 brd ff:ff:ff:ff:ff:ff
17: fwln105i0@fwpr105p0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master fwbr105i0 state UP group default qlen 1000
    link/ether 5e:7e:de:38:ce:36 brd ff:ff:ff:ff:ff:ff
18: vmbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether b8:97:5a:09:75:46 brd ff:ff:ff:ff:ff:ff
    inet 172.16.0.0/12 brd 172.31.255.255 scope global vmbr0
       valid_lft forever preferred_lft forever

/etc/network/interfaces:
Code: 
auto lo
iface lo inet loopback

iface enp5s0 inet manual

auto vmbr0
iface vmbr0 inet static
    address 172.16.0.0/12
    gateway 172.16.0.1
    bridge_ports enp5s0
    bridge_stp off
    bridge_fd 0

/proc/net/dev:
Code: 
Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
fwbr104i0:   27311     541    0    0    0     0          0         0      108       2    0    0    0     0       0          0
fwpr100p0:    9212      72    0    0    0     0          0         0    31600     528    0    0    0     0       0          0
fwln100i0:   31600     528    0    0    0     0          0         0     9212      72    0    0    0     0       0          0
fwbr105i0:   27795     538    0    0    0     0          0         0      108       2    0    0    0     0       0          0
fwpr104p0:    4822      25    0    0    0     0          0         0    30117     517    0    0    0     0       0          0
fwln104i0:   30117     517    0    0    0     0          0         0     4822      25    0    0    0     0       0          0
enp5s0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
fwbr100i0:   32372     599    0    0    0     0          0         0      108       2    0    0    0     0       0          0
fwln105i0:   28345     507    0    0    0     0          0         0     7036      32    0    0    0     0       0          0
 vmbr0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
fwpr105p0:    7036      32    0    0    0     0          0         0    28345     507    0    0    0     0       0          0
veth100i0:    9158      71    0    0    0     0          0         0    31072     522    0    0    0     0       0          0
veth104i0:    4768      24    0    0    0     0          0         0    29685     507    0    0    0     0       0          0
    lo:   39939     406    0    0    0     0          0         0    39939     406    0    0    0     0       0          0
tap105i0:    6982      31    0    0    0     0          0         0    28399     508    0    0    0     0       0          0

Contents of /sys/class/net:
Code: 
enp5s0
fwbr100i0
fwbr104i0
fwbr105i0
fwln100i0
fwln104i0
fwln105i0
fwpr100p0
fwpr104p0
fwpr105p0
lo
tap105i0
veth100i0
veth104i0
vmbr0

Trying to manually bring the interface up with ifup doesn't return an error, but also didn't change any connectivity (or lack thereof). Tried a different ethernet cable to the router to no effect. The router doesn't detect the proxmox machine in its attached devices section, but the front LEDs indicate that it detects a cable connected (likewise the ethernet port on the proxmox machine also has a lit LED that indicates a cable is connected).

I'm at the end of my wits here. Any help very appreciated!
 
hi,

your network configuration looks off:
Code: 
auto lo
iface lo inet loopback

iface enp5s0 inet manual

auto vmbr0
iface vmbr0 inet static
    address 172.16.0.0/12
    gateway 172.16.0.1
    bridge_ports enp5s0
    bridge_stp off
    bridge_fd 0

i would try first with a /24 CIDR and a different IP address for the host... something like 172.16.0.100/24 and make sure the gateway IP is also correct.

on another note you get NO-CARRIER for your ethernet, the cable might be unplugged or broken while you were doing hardware maintenance so i would check this too
 
oguz said:
hi,

your network configuration looks off:
Code: 
auto lo
iface lo inet loopback

iface enp5s0 inet manual

auto vmbr0
iface vmbr0 inet static
    address 172.16.0.0/12
    gateway 172.16.0.1
    bridge_ports enp5s0
    bridge_stp off
    bridge_fd 0

i would try first with a /24 CIDR and a different IP address for the host... something like 172.16.0.100/24 and make sure the gateway IP is also correct.

on another note you get NO-CARRIER for your ethernet, the cable might be unplugged or broken while you were doing hardware maintenance so i would check this too
Click to expand...

Hi thanks for the reply. I think I had two issues here. One was my network config like you said, and I suspect the other is some kind of transient issue with either my motherboard or the physical ethernet port.

I turned the server back on again and noticed that this time, using the same network cable and same port in the router as before that suddenly my VMs were coming up in the attached devices and traffic was available to them. I then made the modifications you suggested (using 172.16.0.100 and changing the mask to /24). With that, I was able to ping the gateway and things are looking good now.

The network config was obviously a misconfiguration, but I suspect there is a transient issue with my hardware as well. So I've ordered a new NIC just in case. Thanks for the tips!
 
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