BUG: Bridge not work with MTU=1500

RouterOS Virtualization
1

I work at an ISP I have a network with many QinQ VLANs because we have many services in place.
I recently migrated from a CCR to CHR,
however when I need to pass packets with a size of 1500 with vlans within a vlan within the bridge it does not pass if the packet is 1500, it does not happen when I place the vlans within ether1 directly without a bridge, but I need the bridges for other operations

I made a laboratory to reproduce the problem, I will pass the script from a CHR and RB2011

obs: the proxmox has jumboframe active and working

script to reproduce the problem:

script in RB2011:

/interface bridge add name=bridge1
/interface vlan
add interface=bridge1 name=VLAN1 use-service-tag=yes vlan-id=1
add interface=VLAN1 name=VLAN2 use-service-tag=yes vlan-id=2
/interface bridge port add bridge=bridge1 interface=ether1
/ip address add address=192.168.1.2/24 interface=VLAN2

CHR script that doesn’t work:

/interface bridge
add name=bridge1
/interface vlan
add interface=bridge1 name=VLAN1 use-service-tag=yes vlan-id=1
add interface=VLAN1 name=VLAN2 use-service-tag=yes vlan-id=2
/interface bridge port add bridge=bridge1 interface=ether1
/ip address add address=192.168.1.1/24 interface=VLAN2
/ping 192.168.1.1 size=1500

CHR script that works:

/interface vlan
add interface=ether1 name=VLAN1 use-service-tag=yes vlan-id=1
add interface=VLAN1 name=VLAN2 use-service-tag=yes vlan-id=2
/ip address add address=192.168.1.1/24 interface=VLAN2
/ping 192.168.1.1 size=1500

I know the answer will be: so use it without a bridge, but I need them to bridge other interfaces

2

Can you please test with smaller packets as well? Quite a while ago, I encountered similar issue, where VLAN-tagged packets were not passing through the bridge in CHR but everything worked fine when I bound VLAN to an ethernet interface. All details here: http://forum.mikrotik.com/t/chr-does-not-transmit-frames-with-vlan-tags-from-bridge/127278/1

If it does not work for you even with smaller packets, it is a proof the proxmox is suffering from the same issue as hyperV where I encountered this bug and it is not about size, but about VLAN and bridge… Since then, I switched CHR to an ESXi and it works fine now.

Just to make sure, I tested your situation with my live CHR on ESXi (sorry, no lab equipment ATM) and I can easily send large (8500) packets through VLAN which is assigned to the bridge.
So it is definitely NOT global bug.

3

yes, with smaller packet 50 works, this fails only when i need to ping in vlan inside vlan with mtu1500