Hi,
Running a proxmox setup where all VMs are bridged to a single physical interface in host, all with default MTU of 1500.
We noticed that websocket connections are closing abruptly, and running the following bash script:
Showed an MTU of 1296 in VMs, while running in host shows 1500.
Any ideas why? Have limited understanding in MTU/MSS, but 1296 is quite low..
ifconfig on host shows everything on 1500:
same thing with VM:
Running a proxmox setup where all VMs are bridged to a single physical interface in host, all with default MTU of 1500.
We noticed that websocket connections are closing abruptly, and running the following bash script:
Bash:
size=1272
while ping -s $size -c1 -M do google.com >&/dev/null; do
((size+=4))
done
echo "Max MTU size: $((size-4+28))"Showed an MTU of 1296 in VMs, while running in host shows 1500.
Any ideas why? Have limited understanding in MTU/MSS, but 1296 is quite low..
ifconfig on host shows everything on 1500:
Code:
enp152s0f0np0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether 3c:ec:ef:b7:fa:8c txqueuelen 40000 (Ethernet)
RX packets 13086020619 bytes 10072373360184 (9.1 TiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 16793858705 bytes 21713322348584 (19.7 TiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
fwbr100i0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether 52:fa:5f:9f:6f:e1 txqueuelen 1000 (Ethernet)
RX packets 99617 bytes 7196620 (6.8 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
fwln100i0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether 52:fa:5f:9f:6f:e1 txqueuelen 1000 (Ethernet)
RX packets 6574036135 bytes 4458682824606 (4.0 TiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 4943211571 bytes 17199642687289 (15.6 TiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
fwpr100p0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether a2:29:04:b5:16:07 txqueuelen 1000 (Ethernet)
RX packets 4943211570 bytes 17199642687223 (15.6 TiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 6574036133 bytes 4458682820130 (4.0 TiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 572662 bytes 70686791 (67.4 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 572662 bytes 70686791 (67.4 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
tailscale0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1280
inet 100.93.48.90 netmask 255.255.255.255 destination 100.93.48.90
inet6 fd7a:115c:a1e0::501:305a prefixlen 128 scopeid 0x0<global>
inet6 fe80::d98d:6ec5:2612:593b prefixlen 64 scopeid 0x20<link>
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 500 (UNSPEC)
RX packets 656845 bytes 110539025 (105.4 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 543198 bytes 426247653 (406.5 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
tap100i0: flags=4419<UP,BROADCAST,RUNNING,PROMISC,MULTICAST> mtu 1500
ether 46:45:f4:6f:6f:df txqueuelen 1000 (Ethernet)
RX packets 4943216384 bytes 17199643015080 (15.6 TiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 6574078516 bytes 4458684523783 (4.0 TiB)
TX errors 0 dropped 890 overruns 0 carrier 0 collisions 0
tap101i0: flags=4419<UP,BROADCAST,RUNNING,PROMISC,MULTICAST> mtu 1500
ether ce:38:e0:2c:7f:53 txqueuelen 1000 (Ethernet)
RX packets 603091249 bytes 454414676344 (423.2 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1003225136 bytes 1944134992270 (1.7 TiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
tap102i0: flags=4419<UP,BROADCAST,RUNNING,PROMISC,MULTICAST> mtu 1500
ether 6e:f9:c3:7a:7e:21 txqueuelen 1000 (Ethernet)
RX packets 72500042 bytes 122667409552 (114.2 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 108024949 bytes 124454557216 (115.9 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
tap103i0: flags=4419<UP,BROADCAST,RUNNING,PROMISC,MULTICAST> mtu 1500
ether 4e:c8:6e:2c:5d:17 txqueuelen 1000 (Ethernet)
RX packets 58501 bytes 4549026 (4.3 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 80886 bytes 364295030 (347.4 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vmbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 1.1.1.1 netmask 255.255.255.248 broadcast 0.0.0.0
inet6 fe80::3eec:efff:feb7:fa8c prefixlen 64 scopeid 0x20<link>
ether 3c:ec:ef:b7:fa:8c txqueuelen 1000 (Ethernet)
RX packets 6126418 bytes 9702077777 (9.0 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 4866497 bytes 9877701568 (9.1 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0same thing with VM:
Code:
enp6s18: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 103.107.198.45 netmask 255.255.255.248 broadcast 103.107.198.47
inet6 fe80::be24:11ff:fe38:5f5c prefixlen 64 scopeid 0x20<link>
ether bc:24:11:38:5f:5c txqueuelen 1000 (Ethernet)
RX packets 110679489 bytes 127374723957 (127.3 GB)
RX errors 0 dropped 1155 overruns 0 frame 0
TX packets 74351454 bytes 125550170072 (125.5 GB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 432 bytes 36844 (36.8 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 432 bytes 36844 (36.8 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
tailscale0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1280
inet 100.96.250.21 netmask 255.255.255.255 destination 100.96.250.21
inet6 fd7a:115c:a1e0::7101:fa15 prefixlen 128 scopeid 0x0<global>
inet6 fe80::b0f7:5995:a771:74c1 prefixlen 64 scopeid 0x20<link>
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 500 (UNSPEC)
RX packets 2809 bytes 244135 (244.1 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 2095 bytes 3034235 (3.0 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0