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Dual WAN routers, DNS servers, failover

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Miner

Regular Contributor
Generic questions for all dual WAN routers:

1-When you have a dual WAN situation configured, and both WANs are configured for 'use DNS from ISP', and each WAN ISP gives the router two DNS servers, which DNS servers do the LAN network clients get from the router and how do the clients determine which DNS servers to use?

2-Network interruption detection. I see various metrics used to flag a failover situation, yet I can't see if this failover is specific to IPv4. Do any of these dual wan routers failover ipv4 and ipv6 separately, such that ipv6 can be in a failover state in wan1 (ipv6 packets then directed to wan2) all while ipv4 continues to work fine on wan1?
 
1) Very much an "it depends" answer, hinging on how you have your DNS forwarding and resolution configured. Very often, for example, one would specify the local gateway itself as the only DNS server, functioning as just a forwarder, which resolves requests by progressively querying the DNS IPs it receives from all WAN connections. This is possible on most any multi-WAN capable platform. Another approach is to use statically-applied DNS routing entries to pull your resolutions, independent of WAN-assigned values. It's all possible and very much just up to how you want your network to function overall.

2) Presuming you had a configurable enough OS, I would imagine you'd be able to setup separate watchdog functionality and conditional scripting for v4 and v6 link checking, which could then trigger separate routing table adjustments for both sets of traffic discretely. That said, I don't see the functionality all that often on more turn-key type platforms, as I'd wager it's a fairly niche use-case.

Hope some of that helps.
 
Yes that does help, thanks.

For question #2 I'm looking for that function to be in the router, for example a cisco rv345. In hindsight yes agree it is a niche use case.
 
If you are in the USA and using a RV345 I would use QUAD9 or Cisco's Umbrella system for DNS. Dual WAN and failover does work but I don't think a RV345 can process two 1 gig internet connections.

The RV345 series also supports a cell backup system. Cisco lists the cells which are compatible.

The RV345 series includes the RV340 and RV345P routers.
 
Last edited:
I looked through my RV340 router dual WAN and Policy Binding Table and I do not believe there is failover for IPv6. Everything seems to be related to IPv4. It could be dynamic and I am not running IPv6.
 

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