Bonding and switching between 2 different Links/WANs/Interfaces

Question

Before I ask anything, I'd like to say that I pretty much searched a lot (to what I know of from keywords and terms such as "bonding" "wans" "links" "failover" "aggregate") and I couldn't find any up to date documentation about it.

Here are the question, basically yes/no: The main Goal: To be able to maintain 0% downtime "while" switching from one source to another - using bonding.

I don't want to use "both" interfaces/links/Wans at the same time, instead I want to use one of them and in case it fails Bonding will switch to the other source.

1- Is there a way to actually bond two different internet connection sources? (using wifi only) let's say i have wlan0 ===> ISP1 and wlan1 ===> ISP2, is it doable same as ethernet?

2- When following online tutorials and guides on how to bond connections they seem to edit /etc/network/interfaces and add the bonding interface, but most of them are requiring a static IP, Netmask and a Gateway. My question is, based on what I should set those static values?

My thoughts are as follow:

If i set bond0 to be static and set the primary interface as wlan0 then it should communicate with ISP1 meaning i must set ISP1's network values. But what if ISP1 goes down? wlan1 will fail to connect because of the wrong static values given to bond0. I know I'm missing something huge in here, but it's what I can think of so far according to the knowledge I have.

3- Can bonding (related to the previou questions) be achieved on a server running Ubuntu/Debian? or I need a router or other type of device?

Ofcourse I'm not asking for any kind of configuration.

Thanks!

Answer 1

I don't want to use "both" interfaces/links/Wans at the same time, instead I want to use one of them and in case it fails Bonding will switch to the other source.

That is not bonding, where you make multiple links look like a single link. What you want is simply what routing does, which is to withdraw a route from the routing table, replacing it with another, less-preferred route.

There are multiple ways to accomplish this, and which method you should use depends on your network topology, configuration, and specific use. For example, simply having two default routes, with one as less-preferred by using something like AD, is very simple, but there could be problems doing that depending on other factors.

You also need to understand the effect on the traffic. If you are using public addressing for your network, then you will be running BGP with your different ISPs to advertise you network(s), and if the link to one goes down, the ISP should withdraw that route, and traffic will come through a different ISP (small delay for convergence). If you are using NAT, then you can break any existing connections because the traffic coming from your network will now have a different IP address, and any traffic coming to you to the old IP address will be lost.

This subject really needs much more than can be provided on this site (chapters or even an entire book). If you edit your question to include more details about how you have your network set up, we could be more detailed in an answer.