How to control bandwidth of LAN segment (allow one segment more than the others) to ISP?

CommCatz used Ask the Experts™
I'm looking for a solution to guarantee a particular LAN segment a particular amount of internet bandwidth.  As an example, if the ISP connection is 100Mbps, then I want allow a segment of the LAN and all of its connected clients to have access of up to 80Mbps and any of the other LAN segments the remaining 20Mbps.  The reason for this is separate organization's cost sharing the price of just one incoming cable broadband ISP.  The current setup is a standard cable modem which then feeds to a SOHO router (primarily used for internal DHCP) and then to a mix of managed (layer2/3 capable) switches to several buildings on campus.  I'm open to adding a capability or replacing any of the current devices that could allow for this type of bandwidth control.
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What you are describing is called QoS and could be configured on the router, but configuration will vary depending on router firmware.  For example, you could even do this with the DD-WRT firmware.  One option would be to enable the other organization to use more bandwidth if it's not otherwise utilized but for their service to get degraded when your organization starts using it.  Another option is to cap them at 20Mbps even if the other 80 are not used.

More detail on this in DD-WRT:


You bring up a good point.  I dont want to cap the other segments at 20Mbps if the bandwidth is available (meaning that they're not contending with the other users at certain times).

My understanding of QoS is protocol or app specific.  Are you thinking that I could associate said subnet with say, http/https and they'd get the priority of the bandwidth over other subnets?
Top Expert 2016

It can also be done at the switch level with a good managed switch
If you take a look at the link for DD-WRT, there are many ways to prioritize traffic with QoS, it does not have to be application or service specific.  The examples in that link go through Prioritization by Application, by interface on the router, by netmask, by MAC address... You could even make those rules time based (i.e. apply during certain times of the day)
Distinguished Expert 2018

What type of router/firewall do you have now? Maybe you have something capable already? If so, we can give instructions based on that. For example, Sonicwalls offer Bandwidth Manager.

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