We're going to let some empty space in our office building soon. The potential client needs an internet connection for their systems (including VoIP).For ourselves we have a resilient ethernet setup, which uses Cisco HSRP to choose which connection is live.

Our primary connection is a 1GB line, but for ourselves we're only using 100MB and our ISP lets us buy additional bandwidth in 100MB chunks. They're only going to have 12 - 20 workers here, so the VoIP traffic will be negligible, and for the rest it's cloud document stores for legal documents.

Between our external routers and our primary firewall we have the SG300, that allows the routers to communicate and keeps all of that stuff on the other side of our firewall.

I'd like just take a feed from the SG300-10PP, and put it into the room that will be the new clients 'server room' as their internet connection. It's outside of our firewall so I think the risk to us and them is pretty low in that sense. The question is (assuming the basic premise isn't fundamentally broken) will a port QoS rule giving them 100MB and us 100MB be robust enough that no one will feel like they're being short changed. Any thoughts and feedback appreciated.

Edit: quick doodle diagram added for clarity

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  • 1
    Could you add a diagram for your planned installation? It's not quite clear how things will get connected.
    – Zac67
    Nov 9, 2018 at 14:28
  • Thanks for the feedback Zac, have added a quick doodle to help out.
    – Saitir
    Nov 9, 2018 at 17:26
  • As far as i know you cant run QoS Policing on a SG300. I would set negotiation to 100 Mbit for each site and then run 1 Gbit to your HSRP routers. Then if you have services you want to priotize via QoS you can set it directly on the port, for instance: voice vlan id 100 voice vlan cos 5 voice vlan dscp 46
    – user36472
    Nov 9, 2018 at 17:53

1 Answer 1


Well, I wouldn't even bother with QoS for limiting bandwidth between client and SG-300 - it should be able to limit the port to 100 Mbit/s without disabling autonegotation. Setting Auto Advertisement to 100 Full should do the trick. Since the common uplink is the exact sum of the downlink speeds it can't be congested.

  • I agree this is a much simpler solution, and the mantra always seems to be 'QoS is too hard to get right!'. This works in this case because the desired limits matched options in the port parameters. Let's hope they never want 2-300Mbp provisioned ;-)
    – Saitir
    Nov 9, 2018 at 18:38

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