[TriLUG] Trying to combine Spectrum and T-Mobile as a more reliable ISP

[Aaron Joyner via TriLUG]

I don't have any specific experience with Endian Firewall (or other canned
solutions), but I can hopefully shed some light on what has to happen under
the hood for this setup to work.

The complication with two residential-class network paths is routing
traffic back on the interface it came to you from (or at least that it is
required to leave on).  A simple single default gateway won't work, because
neither Spectrum or T-Mobile will let you send traffic with a source-IP of
the other network (for many good reasons).

The solution to this is called "policy routing".  Now that you know that
name, a Google Search will turn up a lot of helpful introductions to policy
routing.  The solutions usually boil down to something like this:

$ ip rule add from (ip of Spectrum) lookup Spectrum
$ ip rule add from (ip of TMobile) lookup TMobile
$ ip route add default gw (gateway of Spectrum) table Spectrum
$ ip route add default gw (gateway of TMobile) table TMobile

This has come up a few times on TriLUG over the years, here's a few
examples from the deep archives:
https://trilug.org/pipermail/trilug/Week-of-Mon-20040329/025284.html
(simpler example)
https://trilug.org/pipermail/trilug/Week-of-Mon-20061113/045290.html (a
more complicated example)

If you run into specific complications, ask again for more specific
recommendations.

Best of luck,
Aaron S. Joyner

On Wed, Jun 6, 2018 at 9:15 AM, Charles Fischer via TriLUG <
trilug at trilug.org> wrote:

> Hello All;
>
> Has anybody tried to combine cable modem and tethered cell phone service?
> I am a networking newbie, so if what I am asking for is foolish or
> ridiculously easy, sorry.
>
> After a bit of Google searching, I have decided to try Endian Firewall
> first.  I am willing to learn from other's mistakes.  So if you think I
> should try something else first, please let me know.
>
>
> https://www.endian.com/community/features/
>
> Thanks,
> Charles Fischer
> --
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