Slow outgoing LAN traffic with bridged NICs

Started by pjred

Slow outgoing LAN traffic with bridged NICs   23 November 2015, 06:20

Using latest version on latest build Win 10 64 bit. Just noticed that my LAN traffic from server running BWM to any client is limited to about 16Mbps, whereas traffic to server is 80-90 Mbps.

Running 2 gigabit NIC on server. Tried different NICs same.

If I stop BWM service, then LAN traffic runs full speed both directions. Tried deleting all rules with BWM service running and problem still there. Tried creating allow all rule - still same. Everything else seems to work ok.

Not sure if this problem started with latest version of BWM or latest Win10 build? Used to work ok.

If I tick "Ignore LAN traffic", then the problem goes away, but I get the warning about bridged connection, but everything else still seems to work ok with this ticked. Tried a rule to allow ipv4 based for LAN, but still same. Seems to be the bridging of the NICs causing issue.

I bridge NICs for simplicity of IP-addressing.
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Re: Slow outgoing LAN traffic with bridged NICs   23 November 2015, 15:04

I am not sure why it's limited to 16 Mbps in this case. We haven't really changed anything in this area over a long time.

I suppose in your case the Ignore LAN traffic option can be used and the warning can be ignored. Here is how it works and why we have the warning:

When LAN traffic is NOT ignored: any packets that arrive to a bridged NIC are either accepted by the host or forwarded to the other NIC in the bridge, depending on the target MAC address. This works fine and forwards traffic back and forth as a transparent bridge.

When LAN traffic is ignored, things are a bit different. Any packets, whose source and destination IP addresses fall within the defined range, are processed by the driver and never reach the bridge. This means if you have some LAN hosts on one side of the bridge and some LAN hosts on the other side, they won't be able to communicate through the bridge. This will however work if the server does routing, so even through the packets don't reach the bridge, the IP stack will route them correctly. Likewise, this will work if you have all LAN hosts on one side of the bridge.

So considering the above, I'd assume you can safely ignore the warning and use this option for full-speed LAN.

Re: Slow outgoing LAN traffic with bridged NICs   23 November 2015, 16:02

Thanks for the reply. All my LAN hosts are on one side of the bridge so I will leave it ticked.

Funny how it's just started doing it recently because I've never had it ticked before. I'm suspecting the recent Win 10 major upgrade.

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