Link not switching

I have a problem if the link is not down and the ISP’S uplink down or congested,the link is not switching to the ISP B
Thanks

Need mroe info on the links to suggest a way round this but you might consider the fastest response time algorithm.

(taken from Load Balancing Methods & Algorithms- Peplink)

Hi @MartinLangmaid

Thank you for the reply .What more info required. Two links are fiber, same bandwidth .
same isp. the third link is a microwave with less bandwidth (ISP B).

If I use the Fastest response time, Let’s say ISP has CDN or caching for Facebook and all.
our internal DNS server forwarded the DNS request to ISP-A. So if the pc from the LAN requests DNS for Facebook, it returns the ISP’S A’s CDN IP. When the traffic reaches Peplink, Peplink sends this traffic to ISP B based on the algorithm. So the client pc experience slowness.
Correct me if I am wrong
Thanks for your support .

With fastest response a new session is duplicated and sent to all ISPs. You would expect your two fiber connections to respond quickest - unless they are saturated in which case the microwave link would respond. Whichever one responds fastest will get the continued session traffic.

But first thing to do is edit each WAN link and manually enter the available bandwidth upload and download there per link.

Then test with fastest response and overflow to see which one works best.

Hi @MartinLangmaid

Thanks for the reply. It would be great if you could also address the cdn (caching dns ) part of my question.

Here is my question
If I use the Fastest response time, Let’s say ISP has CDN or caching for Facebook and all.
our internal DNS server forwarded the DNS request to ISP-A. So if the pc from the LAN requests DNS for Facebook, it returns the ISP’S A’s CDN IP. When the traffic reaches Peplink, Peplink sends this traffic to ISP B based on the algorithm. So there is a chance the client experiences slowness?.
If yes how to solve this issue

Thanks

Might happen for the first DNS request, then your DNS server will likely cache for the TTL anyway.
Even if it doesn’t the difference in latency between your fiber and your microwave link to the same CDN will be tiny. I wouldn’t worry about it.

Hi @MartinLangmaid

Microwave belongs to the ISP B. Both ISP has different CDN to Facebook.
Actually, I want if traffic is flowing to ISP-A, let the DNS request forward to ISP-A.If it is flowing to ISP B let the DNS request forward to ISP B
Any possibility to achieve this?
Thanks

You’re going to have to help me understand why this is such a big issue for you - its never been a problem for my deployments and I’m keen to understand your challenge.

Load balancing is session based. DNS sessions, https sessions, VoiP sessions, ftp sessions, they all get load balanced independently, you can’t tie one type to another.

Only way I can think of is to use the overflow algorithm (so use WAN1 until its saturated, then WAN2 then WAN3 etc) DNS would likely follow https sessions to each new WAN as the one before become saturated.