LAN speed issue with Router

[Nuelan]

Hi,

I got a AC87U router with 378.54_2. Router is connected to a switch, and the switch to all my devices.

When the router is unplugged from the switch I can transfer at gigabyte speed from the NAS to a LAN device (~100MB/s). When the router is plugged the same transfer speed drops down to 20MB/s.

Any advice?

 

[highwire]

Hi,

I got a AC87U router with 378.54_2. Router is connected to a switch, and the switch to all my devices.

When the router is unplugged from the switch I can transfer at gigabyte speed from the NAS to a LAN device (~100MB/s). When the router is plugged the same transfer speed drops down to 20MB/s.

Any advice?

I think the switch is at fault here. Is the switch managed or unmanaged? Is it 10/100/1000 or just 10/100? Are you using good quality Cat 5 or 5e cables for all your connections? Log in to your NAS and check that the network interface is actually runnning at 1000Mbps, full duplex. If any of your devices (like your switch) do not support jumbo frames, make sure all your devices have jumbo frames disabled (MTU = 1500).

 

[Nuelan]

Hi,

The switch is a GS108 Netgear gigabit switch, cables are all good quality Cat 5e for every connections, interface is running at 1000Mbps, full duplex. Also jumbo frames is not enabled anywhere...

 

[L&LD]

Is the GS108 at the latest firmware? Have you tried resetting it to factory defaults?

Do you do a full network shutdown and reboot after putting the switch in the LAN? Seems weird that this would work, but I have seen this 'solve' otherwise hard to track down issues (maybe due to static?).

 

[Etz]

Is the GS108 at the latest firmware? Have you tried resetting it to factory defaults?

Netgear GS108 is Unmanaged switch, hence you cannot upgrade firmware, neither it has reset button as there is nothing to reset.

 

[L&LD]

Netgear GS108 is Unmanaged switch, hence you cannot upgrade firmware, neither it has reset button as there is nothing to reset.

My mistake, I thought it was just the series not the actual model.

 

[Nuelan]

As stated, GS108 is unmanaged. I tried to turn it on and off but it didn't help.

I'm trying to understand what is happening. When the router is unplugged, packets are sent directly from the NAS to the LAN device. Is it expected to be different when I plug the router? Does the presence of the router forces packets to travel through it? In other words, for LAN traffic, do the packets go from the NAS to the switch, then from the switch to the router, then back from the router to the switch and then from the switch to the device?

 

[L&LD]

Are you creating any loops with the LAN ports and all your devices?

Could you give us a simple diagram?

 

[Etz]

Actually, this sounds like you are having multiple links between, ether Switch and Router or switch and NAS...

Are you sure, you are using single cable for each device?

 

[Nuelan]

this is the diagram

 

[Etz]

Well, traffic from PC to NAS should not traverse link between Switch and Router according this, as switch has mac address table for this communication.

Only DHCP, etc request should be forwarded to router.

 

[eddiez]

Well, traffic from PC to NAS should not traverse link between Switch and Router according this, as switch has mac address table for this communication.

Only DHCP, etc request should be forwarded to router.

And how does he achieve that?

 

[Etz]

And how does he achieve that?

Magic?

Thats the beauty of such setup, it will just work this way.
Actually same goes for router LAN ports, communication between those is handled by switch ASIC, they won't go trough Router CPU as there is no need to. Those packets have shorter path available, hence they are not forwarded to Router CPU, unless they are directly destined to router IP address or broadcasted to entire network.

 

[eddiez]

Magic?

Thats the beauty of such setup, it will just work this way.
Actually same goes for router LAN ports, communication between those is handled by switch ASIC, they won't go trough Router CPU as there is no need to. Those packets have shorter path available, hence they are not forwarded to Router CPU, unless they are directly destined to router IP address or broadcasted to entire network.

Thanks. That's the additional information the TS needed to know. Your previous reply was a bit unclear as to the correctness of his setup

 

[Nuelan]

Thx.

Now I need to understand what is actually affecting my transfer rate when the router is plugged. I will do more testings.

 

[mattiL]

I guess that you have fixed IP addresses on most nodes, is there any chance of an IP address conflict?

 

[wiak]

did you try setting all the devices to 1000 full duplex in device manager? that way all the devices are forced to gigabit speeds

 

[Nuelan]

did you try setting all the devices to 1000 full duplex in device manager? that way all the devices are forced to gigabit speeds

I'm not sure to understand what you mean. When the router is bypassed the transfer is made at full speed. It only drops when the router is plugged. And in the router settings it shows 1000 full duplex.

 

[Etz]

Just a mind flash, by any case...do you have STP (Spanning tree) in Router enabled under LAN?

 

[Nuelan]

Just a mind flash, by any case...do you have STP (Spanning tree) in Router enabled under LAN?

Yes it is.