Are there true benefits to load balancing Dual Wan?

matthew johnson

Regular Contributor
I know a lot of routers now a days support dual Wan. Is there really any true benefit to its load balancing mode? Does it help with like ping and jitter and stuff like that? Are there any drawbacks on performance of the router? Like heavy cpu load? Ive googled stuff about it but cant seem to fine definitive answers?

Edit = I dont know why i posted this here meant to post in regular ASUS forum.
 

ColinTaylor

Part of the Furniture
Dual WAN load balancing is mostly of benefit if you have lots of clients using the connections at the same time. Think of an office with 20+ users all of whom are using the internet. The connections to the internet would be spread randomly across both links making the most of the combined bandwidth. For one or two individual users there's no great benefit. It doesn't affect ping or jitter. It won't make your online gaming any better (if anything it could cause problems).

You can of course fine tune connections for specific hosts using routing rules if you have two connections with greatly different bandwidths. I'm sure people can come up with scenarios where it's particularly beneficial but it would have to be assessed on a case by case basis.
 

Tech9

Part of the Furniture
I know a lot of routers now a days support dual Wan.

Asus routers advertise Dual WAN as an option, but it doesn't work as expected.

 

matthew johnson

Regular Contributor
Dual WAN load balancing is mostly of benefit if you have lots of clients using the connections at the same time. Think of an office with 20+ users all of whom are using the internet. The connections to the internet would be spread randomly across both links making the most of the combined bandwidth. For one or two individual users there's no great benefit. It doesn't affect ping or jitter. It won't make your online gaming any better (if anything it could cause problems).

You can of course fine tune connections for specific hosts using routing rules if you have two connections with greatly different bandwidths. I'm sure people can come up with scenarios where it's particularly beneficial but it would have to be assessed on a case by case basis.
Why do you say it could cause problems for gaming?
 

ColinTaylor

Part of the Furniture
Why do you say it could cause problems for gaming?
It's a possibility. If you're playing a multiplayer online game the connections between you and the other players usually need to all be over the same WAN interface. If there's some confusion in the setup process and clients try to connect over the "other" WAN interface they will probably fail. In reality this is not that likely, but it's a possible problem that doesn't exist in a single WAN setup.
 

drinkingbird

Very Senior Member
I know a lot of routers now a days support dual Wan. Is there really any true benefit to its load balancing mode? Does it help with like ping and jitter and stuff like that? Are there any drawbacks on performance of the router? Like heavy cpu load? Ive googled stuff about it but cant seem to fine definitive answers?

Edit = I dont know why i posted this here meant to post in regular ASUS forum.

Yes, there is a huge benefit, it gives you something to consume lots of your time tweaking when you're bored....

As mentioned it is not combining your bandwidth, a single download for example will not get the combined bandwidth. Multiple connections will be able to take advantage of it but that can result in packet sequencing issues due to differing latency between the two, which will either increase your overall latency or completely break your connection depending what you're connecting to.

In an environment where it is mostly web/general use traffic with lots of users, it is a great solution, but even then you could see some issues with sites that will use your IP to keep you on the same server. I.e. you start filling out an account application, click next, establishes a connection to a new site on their side, sees you coming from a different IP, and loses your information. Many sites use cookies to try and avoid this issue but not all. Or the example given before of gaming where you have multiple connections and it won't like that some are from different IPs. File sharing works in much the same way.

With enterprise hardware when this sort of thing was needed (before you could get massive internet connections cheap) you would enable route caching so one client would always stick to that one interface, the next client would always stick to the other. You could try to force this behavior with some static routes but that gets pretty complex and hard to manage and not sure if asus's routing is robust enough to do policy/source routing.

I haven't used it on Asus but have heard of it being problematic, but maybe with newer code they'll start forcing some "stickiness" or route caching to make it work better.
 

ColinTaylor

Part of the Furniture
@drinkingbird Packet sequencing and some of the other issues you mention shouldn't be a problem. IIRC Asus moved from a connection based (iptables) solution a few years ago to a weighted route (iproute2) solution.
 

drinkingbird

Very Senior Member
@drinkingbird Packet sequencing and some of the other issues you mention shouldn't be a problem. IIRC Asus moved from a connection based (iptables) solution a few years ago to a weighted route (iproute2) solution.

As long as it sticks all traffic for a client (both inbound and outbound) to the same interface, then it should work fine. You had mentioned that multiple connections to a game could potentially go over different interfaces so I assumed that was not the case, that it was connection based round robin or that it was only "sticking" connections with the same source/destination IP to an interface and if the destination changed that could go over the other interface. I haven't used it personally on Asus but have done various load balancing setups on Cisco and other branch office setups.

Though if your two ISPs are differing speeds and/or latencies, it could negatively impact your experience, sometimes things are faster than others etc. For a few clients it probably isn't worth setting up, if there are quite a few and they are using a lot of bandwidth, it might be worth a try, especially if your two ISPs both have decent speed and latency.
 

Ranger802004

Very Senior Member
It's a possibility. If you're playing a multiplayer online game the connections between you and the other players usually need to all be over the same WAN interface. If there's some confusion in the setup process and clients try to connect over the "other" WAN interface they will probably fail. In reality this is not that likely, but it's a possible problem that doesn't exist in a single WAN setup.
That's not an issue because the same session is tracked with FWMarks and so the same session would stay going over the same WAN Interface. There are problems with the firmware creating this FWMark rules though and my script handles resolving that part.
 

ColinTaylor

Part of the Furniture
That's not an issue because the same session is tracked with FWMarks and so the same session would stay going over the same WAN Interface. There are problems with the firmware creating this FWMark rules though and my script handles resolving that part.
Initially I only mentioned this as an aside as a possibility. I didn't really want to emphasise this but people seem to have been picked up on it. Yes, I know sessions are tracked and go over the same WAN interface. I said this above. I was thinking of a hypothetical situation where for example, an application uses STUN over WAN1 to determine its public IP address. It connects to some sort of game or proxy server on the internet using WAN2 but registers its presence using the IP of WAN1 instead of WAN2. As I said above, "In reality this is not that likely, but it's a possible problem that doesn't exist in a single WAN setup". I wish I hadn't mentioned it now. :rolleyes:
 

Ranger802004

Very Senior Member
Initially I only mentioned this as an aside as a possibility. I didn't really want to emphasise this but people seem to have been picked up on it. Yes, I know sessions are tracked and go over the same WAN interface. I said this above. I was thinking of a hypothetical situation where for example, an application uses STUN over WAN1 to determine its public IP address. It connects to some sort of game or proxy server on the internet using WAN2 but registers its presence using the IP of WAN1 instead of WAN2. As I said above, "In reality this is not that likely, but it's a possible problem that doesn't exist in a single WAN setup". I wish I hadn't mentioned it now. :rolleyes:
I used the load balancer mode quite a bit when testing and developing my script, once I got the issues resolved with the firmware making the proper rules it worked great and my connections properly tracked over the respective WAN interfaces, not as well put together like an enterprise level load balancer like F5s but not bad.
 

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