Act as IP Router

I have been experimenting with 5.28 IP routeing.

It works as a simple NAT router connected to an Internet modem.

I now have it connected to two Internet modems and I have it doing a very simple static route.

For example, my routes file has the line
route -e add -host google.co.uk 10.0.128.7

This works and traffic to google from all of my computers is routed to Google via the EE mobile modem rather than the ADSL modem.

But that seems to be the limit of its capabilities. Adding a second line to the routes file to route BBC traffic to the same EE modem achives nothing.

Is that to be expected or am I missing something.

Some example files might be nice.

Adding a second line to the routes file to route BBC traffic to the same EE modem achives nothing.

Let’s have a look.

% nslookup bbc.co.uk
Server:		8.8.4.4
Address:	8.8.4.4#53

Non-authoritative answer:
Name:	bbc.co.uk
Address: 151.101.0.81
Name:	bbc.co.uk
Address: 151.101.64.81
Name:	bbc.co.uk
Address: 151.101.128.81
Name:	bbc.co.uk
Address: 151.101.192.81

% nslookup google.co.uk
Server:		8.8.4.4
Address:	8.8.4.4#53

Non-authoritative answer:
Name:	google.co.uk
Address: 142.250.187.195

google.co.uk provides only one IP address, while bbc.co.uk provides 4.

“route add” will almost certainly be adding only the first IP address supplied, while the client could be using any of them. Bear in mind that the client will be doing its own DNS lookup, so may see the IP addresses in a different order, or even completely different IP addresses.

Good point. But ….

I would like to use IP addresses or even ranges instead of the host name, but the Route documentation is not clear about the format, which is why I hoped I might get some examples.

google.co.uk provides only one IP address, while bbc.co.uk provides 4.

Eight for bbc actually, but the first 4 listed are IPv6. Similarly google is two (IPv6 and IPv4)

What does route -e add -net 0.0.0.0/0 10.0.128.7 do in this experiment?

What does route -e add -net 0.0.0.0/0 10.0.128.7 do in this experiment?

Stops the Pi 4 from booting – with error message File Exists

However,
route -e add -net 5.0.0.0/8 10.0.128.7
routes traffic to my website via EE mobile, leaving everything else to go vi ADSL (10.0.128.1)

adding a few more

route -e add -net 5.0.0.0/8 10.0.128.7
route -e add -net 151.0.0.0/8 10.0.128.7
route -e add -net 142.250.0.0/16 10.0.128.7

Thank You for that.

Incidently,

google.co.uk provides only one IP address,

I am seeing a lot more addressees for google.co.uk

but I do not have accees to nslookup

file exists

where is the file?

I am seeing a lot more addressees for google.co.uk

You will do. Google has many servers spread all around the world, so a degree of load-balancing and/or “closest physical server” will result in different addresses being delivered, albeit one at a time.

For example, further upthread I gave an example of looking up google.co.uk on Google’s own public DNS server (which gave an answer of 142.250.187.195). When I retried the same lookup on my ISP’s DNS server, I got a different result (142.250.180.3). This is to be expected.

where is the file?

It’s a confusing error message: I’m almost certain that it should say “route/entry exists” rather than “file exists”. When you’re using DHCP to get a local IP address, the DHCP module will give you a “free” 0.0.0.0/0 route, pointed at the default router for your subnet. This is not a problem while you’re adding more specific routes, but when you attempt “route add” for a network already in its tables, it will generate an error.

It is all looking good.

Thank You, Stuart, et al.

Files

I would would suggest that there are file(s) somewhere which hold the routing tables as these are maintained over a reboot/powercycle.

route -e flush
clears the tables (reporting what was deleted), including the gateway default. this is remembered over a powercycle.

route -e add -net 0.0.0.0/0 10.0.128.1
puts it back again and this is remembered over a powercycle. So, knowing how/where this is saved would be nice.

I think it’s saved in Choices:Internet, or less likely ! Boot.Resources.! InetDBase. I think it just collects the *route commands you entered in an Obey file.

I now think that I have been seeing more of a problem than is really there.

I can now say that it is all doing what I would like it to do. In two other topics I slso asked for help or comment on USB Ethernet adapters and headless running. I can now say that this headless multi-subnet Pi 4 is working very well.

I think the only bit of all of this that will be of general interest is that I now have all of the household ¹ Google ² traffic being routed over a dedicated EE mobile service instead of my FTTC static IP internet service.

¹ Windows PCs, Ipads, Smart TVs, etc as well as a few RO desktops.

² Google, Facebook, Twitter, etc.