Data ports and maximum number of bearers

[Bjørn Mork]

Carlo Lobrano <c.lobrano at gmail.com> writes:

> Hi everybody,
>
> I tried the steps Bjørn suggested and it worked, even if I'm not sure about
> some points.
>
> Firstly, I can get the address of api.ipify only if the eth (or another
> connection) is still up, not sure if this is expected or you got that IP
> from one of the mbim connections.
>
> Secondly, and more important, I can't figure out how to configure routing
> tables.

Well, this is really a question related to dealing with multiple network
interfaces in general. The answers depends on what you have at each end,
and how yout want to connect it. Some possible solutions are

 - single routing table with non-default routes out the appropriate
   interfaces
 - multiple routing tables with default routes, using ip rules to select
   the appropriate table
 - VRF lite: https://www.kernel.org/doc/Documentation/networking/vrf.txt

and probably more...


> I googled a lot, the most interesting solutions consider adding new
> tables in /etc/iproute2/rt_tables and configuring the sessions gateway
> separately in each table,

Yes, that's one possibility, mostly suitable if you can create simple
source address based rules to select one table or the other.  Note that
you don't really have to add any symbolic names to rt_tables for testing
this.  You can use table numbers directly.

> and some rules to route the appropriate range of
> IPs to the right table, but still I can not ping any other address.
> Following is my last configuration attempt, any hint is appreciated.
>
> Note that I had to use the main NET and only 1 vlan (with ID different from
> 4096) for other constraints
>
> $ ip route list
>     5.92.161.0/24 dev wwp0s20u1u2u4  proto kernel  scope link  src
> 5.92.161.124
>     10.62.211.0/24 dev wwp0s20u1u2u4.0  proto kernel  scope link  src
> 10.62.211.182
>
> $ ip route list table table1
>     default via 5.92.161.1 dev wwp0s20u1u2u4
>     5.92.161.0/24 dev wwp0s20u1u2u4  scope link
>
> $ ip route list table table2
>     default via 10.62.211.1 dev wwp0s20u1u2u4.0
>     10.62.211.0/24 dev wwp0s20u1u2u4.0  scope link


There are no layer 2 addresses on MBIM, so you can simplify these to

$ ip route list table table1
    default dev wwp0s20u1u2u4
$ ip route list table table2
    default dev wwp0s20u1u2u4.0

Not that it matters. Just to keep things as simple as possible.

> $ ip rule
>     0: from all lookup local
>     32763: from 10.62.211.0/24 lookup table2
>     32764: from 5.92.161.0/24 lookup table1
>     32765: from 5.91.109.0/24 lookup table1
>     32766: from all lookup main
>     32767: from all lookup default


So with these rules in place, you should be able to do

 ping -I 5.92.161.124 8.8.8.8
 ping -I 10.62.211.182 8.8.8.8

and the two pings would go out on wwp0s20u1u2u4 and wwp0s20u1u2u4.0
respectively.

But whether this is what you want is another question.  Juggling
multiple default routes is tricky.  But if there is a distinct
dependency between source adress and outgoing interface, then your
solution is suitable.  The remaining issue is of course that you have to
be explicit about source address selection everywhere...



Bjørn