On Mon, 17 May 2021 14:35:41 -0400
Hendrik Boom <hendrik@???> wrote:

> I now have a new VDSL connexion now, which is supposed to go at
> 25Mbits/sec downstream and 10 Mbits/sec upstream. Bell has been here
> and has checked that it is working, using their modem.
>
> Now I'd like to get it to actually work, which means that *my* modem
> has to be able to talk VDSL.
>
> It turns out that I have to reconfigure the modem, and I have
> instructions to do that.
>
> The first step is to use a browser to connect to http://192.168.1.1
>
> Now that means I have to configure my routing tables so that packets
> to 192.168.1.1 will go to port ethv0, which is where the modem is
> connected.

My 2c here.
All the commmercial moden/routers I've been using since I moved from
copper line dial up all havve default IPv4 addresses similar to what
you quote.

Until recently*, a simple "arp -s hostname MAC-address" was sufficient
to enable some comms to enablt telnet or browser to communicate with it
enough to set it with an IPv4 that brought it into your current IPv4
after a reboot.

Caveat, you may needs to open the netmask on the computer you wish to
configure it from e.g. 255.255.255.0 to 255.255.0.0.

I use 192.168.x.y as our IPv4 SOHO LAN and we run static IPs, so it is
a relative simple matter to either etc /etc/network/interfaces or swap
them around to one that already has the wider netmask.

Tip; when I retire a modem/router, I usually change the working IPv4
from the active portal to a range of retirement IPv4s, which are
listed in /etc/hosts. This way, should you ever have to quickly draft
the old modem -router back into harness, you can communicate with it
ASAP once you plug it back into the network.


>
> One or two routing table entries should do it.
>
> I have found several authoritative-looking web pages on instructions
> to display and edit the routing tables.
>
> But none of them explains what the routing tabe entries *mean*.
>
> Anybody have some Linux routing experience or links to explanations?
>
> The last time I had to mess with any of this was about 15 years ago,
> and I've quite forgotten the details.

Try "sudo route -n" to see your current routing table.
I've munged mine below.

Kernel IP routing table
Destination   Gateway       Genmask     Flags Metric Ref    Use Iface
0.0.0.0       192.168.X,Y  0.0.0.0       UG    0  0          0 eth0
192.168.0.0    0.0.0.0         255.255.0.0    U    0  0       0 eth0

You will notice, I still have the netmask on this machine at
255.255.0.0 (/16?) from the last modem-router configuration.

Then after it is just a series of sudo route -add commands, in theory.
YMMv depending on your LAN. I've found the netmask fiddle best for me
as it isn't something I do regularly either.

* I recently found that you can not arp to the newer Netgear
modem-routers. Given the abysmal ingress filtering ability and
the configure by smart phone route they push, that brand is on my
POS list. I've always had good service from Billion.