Re: A smart router for more than one default routes

Linux Advanced Routing and Traffic Control

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This is not really the best place for a routing question. If you raise
your question on the quagga list, you might be better off.

On Wed, Feb 25, 2015 at 10:39 PM, Han Changzhe <hcz@xxxxxxxxxxx> wrote:
> Hello experts,
> I'm setting up a routing server on Linux with following links
> 1. An Ethernet link (eth0) to the 1st internet link (fast, but can't
>    access some sites);
> 2. A VPN link (tun0) to provide services to local users;
> 3. A VPN link (tun1) to a proxy server as the 2nd internet link (slow,
>    free).
> My target is:
>   * for common internet access, routing the packets through eth0;
>   * for the sites can't be accessed through eth0, routing them through tun1.

Well, one of the things we have been working on in the homenet working group is
source specific routing, which could possibly help here, but it is

> By now, I set the routing table manually for serveral sites and it works
> fine. Because there are thousands of them and the sites change with time, so
> I want a better solution.
> My idea is like this: setting up more than one default routes for internet
> access, then dynamically change the route table (or route table cache) with
> some software according to the internet access results.
> For example, if we get a timeout from through eth0,
> the software should try it through tun1 link and, when succeed, adding the
> later route to current route table.

Well you are conflating several layers of the protocol here.

It is hard to recognise a timeout, for example, without sniffing for
on the gateway. That sniffer could simultaneously try a syn out one of
the vpn interfaces and if a syn/ack is not received from the main
interface, and one IS received from the vpn, insert a route for it.
You would still need to clean out that table periodically.

Then you would to insert and delete rules for each ip (or more likely
network) you wish to reroute
based on your measurements of what is working or not, and to otherwise
fall back to the default ethernet route.

Say for example you could not get dns from locally.

ip route add dev tun0

This doesnt help you on any protocols except tcp. udp apps are
different. so is quic, etc.

a bulk method would be to go through the alexa top 1 million to see
what you could and could not access, and set up routes for each (but
this does not handle your desire for 2 tunnels)

> I don't know if any routing software on Linux work as I expected. I tried
> quagga with zebra + ospf but not successful.

ospf? oy, no....

> FYI, it's not a common case for link based fail-over/load balance.
> Please give me suggestions!

Well, my way would probably involve a squid or polipo web proxy to
make the failover case easier. A lot of users would not dig that...

> Thanks in advance,
> Changzhe
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Dave Täht
Let's make wifi fast, less jittery and reliable again!
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