Adding a router (or switch) between two separate networks


Jan 10, 2016
Okay, so this... could be a wireless or wired networking thing, but I think mostly it's a wired networking thing.

So, I work at a hotel... this hotel has a guest network which is ran as so:

So, I am wondering if adding a wired router as so:

Would this benefit my traffic without affecting the Guest Network assuming that he has it set auto configure IP address? The modem does give a static IP address; however, I have switched the ports before and the guest network was not affected so I am assuming that he has it set to auto configure?

Main goal here is to lessen the latency of my traffic by lowering the priority of the overall guest network and/or routing specific ports directly to my router.
The problem with your theory is you can't actually prioritize traffic coming from the internet. If the link coming to your site is full the ISP will randomly discard or delay traffic. By the time any equipment you have control over see the data the damage is already done you can not undelete something and discard something else. Everything you see regarding priority is for transmit upload

There are some QoS tricks you can use to some extent limit traffic and it works ok for many times of traffic but it works poorly on the worst offender line torrents. Everything you are doing is not truly Qos it attempts to trick the end stations into limiting the amount of data they request.

Although you could put QoS on the a wired router as you indicate the problem is it has no way to know how much the 2 other machines connected to the modem...I suspect the device is a using. To really work effectively the QoS needs to be on the device with the connection to the internet.

You can try it but the concept of priority is not how it works. You either set the other machines to some hard coded limitation or you attempt to set your machine to some guaranteed bandwidth. It depends a lot on how the QoS is implemented. Both require that you know how much bandwidth is available to your router which you do not really know since it can be used by the 2 other pc. You could just ignore this but Qos is already not real effective in many situations.


Jan 10, 2016

Okay... so, I get what you are saying, but throttling the uplink would domino effect throttle the downlink, correct?

Say, I were to put a managed switch or router in front of all the computers/guest network, gave my router a static IP address and wouldn't I then be able to prioritize all traffic coming/going to the WAN vs my router? AND/OR be able to actually prioritize certain ports to go directly to my router quicker than they are currently.

If not, how would I be able to prioritize better or better improve the throughput/latency of the current setup so the network doesn't interfere as much... is that possible? Or is drilling a hole and running CAT6 be the only way?
There is no delay that you can measure in a lan network. Ports on the router can all run at 1gbit up and 1gbit down all at the same time. If you have 4 ports on the router each can actually be transferring 2gbit of data total so the router/switch can pass 8gbit of traffic constantly.

The problem comes when you try to send it on the internet link which is slower. The packets all arrive to the router and get put in a memory buffer. This is where QoS comes in. You can control the order the packets are placed in this memory buffer.

Traffic coming the other way from the ISP never gets put in a buffer on the router. There is always space to send the traffic immediately to the end station because the ports are so fast compared to internet connection.

There is no effective way to limit download speed by modifying upload speeds unless you pretty much block the upload. Lets take a example.

The stations sends a small packet that says web site give me file xxxx.
The server then send 1500 byte packets of data. The end station send minimum 64 byte packets to acknowledge this. So I download 1500 bytes for ever 64. You would have to limit the upload to less 20 to 1. Now file transfer is actually much smarter than that. It will send more and more data with only a single acknowledgement. The limit used to be 65000 bytes so now you are at 1000 to 1. The newest methods increase that number even more. It technically is possible for the server to send enough data to saturate your connection and receive only 1 acknowledgment packet.

For QoS it's not true that it doesn't buffer on the router. TCP downloads shape very well with QoS. If you have a 100Mbs link and you limit it to 90Mbs it's very unlikely anything buffers upstream. AQM drops the TCP packets and those connections slow down fast enough that your link doesn't hit 100Mbs.

Only in a very small number of case. Router can process data extremely fast. If the data comes in at 100mbps and it has gigabit port to the internal switch chip it will be sent immediately. There will be no data to choose from. You might get data queues in the buffer going to the wifi radio chips. The problem many times is this data buffer is in the radio chip and the cpu chip can not see the queue and do anything about it even if it wants to. It depends on the chipset.

AQM is a QoS setting mostly for dummies. It is a simple check box for people who do not really want to be bothered with the details of how to setup QoS. It is mostly for "gamers" since it thinks all equal. It requires many other settings to really work effectively.

But it still does not matter in almost all cases. If you have 100mbps coming in from the ISP and 1000mbps going out to the end users there is no queue to manage. The actual queue is in the ISP router where it is trying to the data in to the 100mbps connection. You can not directly affect the queue in the ISP router.

Do you have anything to back this up? Set a limiter to 1% of your ISP download and show that you can't slow down your download side on a TCP speedtest. If what your saying is true the limiter won't do anything.
barefin if you want a good shaper I recommend ipfire. It has everything you need to monitor and configure class based rules in addition to AQM to keep your latency low on gaming.

All traffic needs to go through it for it to work. The way your diagram is setup has two computers on the modem.

You are being overly simplistic here. You are now saying IF you place a limiter in the router that is below the rate the ISP has committed it will buffer the traffic. I clearly said there were QoS tricks but it is not that simplistic.

I was going to post a longer response here but I am not even going to bother. Most your responses to QoS are everything is bufferbloat and all users are gamers. QoS is not a one size fits all which is why commercial router do not even have the AQM and other silly 1 click options.

fq_codel+htb or cake is a complete shaper. it's 1 click works well for most people though.
The OP is trying to fix bufferbloat and these are the only qdisc that actually do anything for it.

ipfire is unique because it's the only implementation that took the time to build out it's gui for class based rules.

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