Oversize packets from pve:8006

keeka

Active Member
Dec 8, 2019
199
24
38
I recently aquired a new switch that has various MIB counters (Zyxel GS1900). Everything looks good part from one metric, etherStatsOverSizePkts.
This is only non-zero on the two VLAN trunk ports I have configured on the switch. For one of these ports in particular, it runs into the 10's of millions after a few hours uptime. This switch port is connected to vmbr0 on pve host.

Running a packet capture on the associated proxmox bridge, filtering for packet size, there are two primary sources of over size packets. Both are in the order of 2500 octets.
One source is an mjpeg stream from an Edimax IP camera where I am unable to check/modify the MTU. The other source is from pve host port 8006. and unsurprisingly, only appear when I am accessing the proxmox web UI. The host management interface is a vlan, on this bridge. All bridges below connect to a pfSense VM. However I don't believe the traffic concerned touches that VM.

I have checked MTU across VMs, CTs and host. Nothing no non default MTUs as far as I can see. So I do not understand why proxmox host interface generates overize packets. Any explanation or advice appreciated.

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

iface enp5s0 inet manual

iface eno1 inet manual

auto vmbr0
iface vmbr0 inet manual
        bridge-ports enp5s0
        bridge-stp off
        bridge-fd 0
        bridge-vlan-aware yes
        bridge-vids 2-4094
#LAN

auto vmbr1
iface vmbr1 inet manual
        bridge-ports eno1
        bridge-stp off
        bridge-fd 0
        post-up /usr/sbin/ethtool -K eno1 tso off gso off gro off rxvlan off txvlan off
#WAN

auto vmbr2
iface vmbr2 inet manual
        bridge-ports none
        bridge-stp off
        bridge-fd 0

auto vmbr3
iface vmbr3 inet manual
        bridge-ports none
        bridge-stp off
        bridge-fd 0

auto vmbr0.10
iface vmbr0.10 inet static
        address 192.168.0.3/24
        gateway 192.168.0.1
#PVE


Code:
vmbr0.10@vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 46:68:0f:6b:3e:e8 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.3/24 brd 192.168.0.255 scope global vmbr0.10
       valid_lft forever preferred_lft forever
    inet6 fe80::4468:fff:fe6b:3ee8/64 scope link
       valid_lft forever preferred_lft forever
 

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