How does one configure the web-facing part of a small business network for redundancy and quality of service? I mean ... we can have the control over our internal infrastructure, but what happens when it comes to the WAN links?


  • Small business with < 20 user devices connected and a small budget
  • They have a LAN for users
  • They also have a private network with some virtual servers, including a VoIP based PBX.
  • Couple of servers will probably be migrated to the cloud in the future, but most of them will stay on-premise.
  • They already have a firewall appliance that is used as a gateway for both private subnets.


  • They want two Internet uplinks for redundancy (on different technologies and/or different ISPs).
  • They cannot afford enterprise grade connections, so the bandwidth of the two links can be susceptible to changes over time (as it happens for DSL connections). Also, the links will have different bandwidth one from each other. That said, they will be quite fast, quite stable and with a decent latency.
  • They need public subnets for web-facing servers in their network. These subnets need to also work on failover links, so that their servers will be reachable by IPs even during the downtime of their main connection. This is especially critical for the VoIP system. I know that some ISPs provide public subnet preservation for failover links. I also know that sticking to a single provider would reduce redundancy in case of failure on the ISP side.
  • They need QoS both for VoIP and for other classes of traffic.


  1. How do you configure QoS in a situation where available bandwidth is unknown and/or can change over time?
  2. How do you preserve subnets over multiple connections? Are there any low-budget alternatives to the single ISP solution?
  3. If you go the single ISP way (that would preserve subnets), I would expect the ISP to either (A) provide a router that combines the two links or (B) provide two routers (one WAN link each) that will talk to each other using first-hop redundancy protocols. How can you configure QoS so that it works both for main and for secondary connection (that have different speeds)? How do you prevent double NAT, especially in the case B where you have first-hop redundancy?
  4. How do people generally solve these types of challanges? Do they leave firewall and QoS configuration to the ISP to manage?
  • QoS on LAN only or on WAN as well? What do you mean by "preserve subnets" - what is your problem? Where is double NAT a problem? Do you refer to CG-NAT?
    – Zac67
    Commented May 13 at 9:10
  • @Zac67 I can handle QoS on the LAN myself, and it's generally not big of a problem because the internal network will hardly be congestioned. What I need it is to prevent, for example, quality degradation on VoIP calls when the WAN link gets saturated by other activities. This also applies to other classes of traffic (e.g. VPNs must have priority over regular internet surfing).
    – iDontKnow
    Commented May 13 at 9:29
  • 1
    That is the purpose of QoS on the LAN. You control the bandwidth use of the desired protocols on the LAN at the edge of the network. Once traffic leaves your equipment, there is no way to control it for your needs anymore. Commented May 13 at 12:19
  • Repeat after me, "There is no QoS on the public Internet!"
    – Ron Maupin
    Commented May 13 at 12:45
  • @FrameHowitzer Yeah sure, I was refering to the edge of LAN.
    – iDontKnow
    Commented May 13 at 12:50

1 Answer 1


The bad news:

Without enterprise-grade circuits, you can't have QoS on the WAN. You can't control the QoS on the provider's network and they will very likely ignore any QoS signalling attempts you make.

The good news:

It often doesn't matter. If you've ever used a product like Google Voice, MS Teams, FaceTime, Facebook Messenger, etc. You know that voice quality on the Internet is acceptable most of the time without QoS. Any periods of poor voice quality are likely to be transitory.

There are many ways of handling failover with multiple ISPs, but they all involve additional equipment/expense that you may or may not be willing to incur. If you're planning a migration to the cloud, you might consider a load balancer-as-a-service to route connections to your active circuit.

  • As I said in the comments below the original post, my goal it is not to control the QoS of my packets inside the provider's network, but only on the edge of the my own network. Also, the main goal it is to preserve my public IPs when the main connection goes down. If I have two different ISPs and my main connection goes down, my servers are not reachable anymore because their public IPs were tied to that ISP. If I have a single ISP, then I cannot control QoS on the edge, and I also lose redundancy by not having different providers.
    – iDontKnow
    Commented May 13 at 13:07
  • I understand, but there's nothing to control. Any contention on your circuits will happen before the data reaches you, and there's nothing you can do about it. As I mentioned, there are techniques to provide a redundant address, but they all require purchasing equipment or services. None of them will be available on consumer-grade circuits.
    – Ron Trunk
    Commented May 13 at 13:11
  • Yeah, you either need to move your critical services to 'the cloud' or a colocation/datacenter environment where you can have more options that available at the average home/small business location or you can simply throw money at the problem but by that point you might as well have used the many service options already available. Ultimately, it is far easier and more economical to simply pay for good service from professional providers (VOIP, etc.) and then just buy enough internet service bandwidth that QoS is not an issue you need to worry about. Commented May 13 at 14:04

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