Posts: 1
Joined: Fri Jun 29, 2018 3:13 pm

Two internet connections

Fri Jun 29, 2018 3:25 pm

Hello everyone,
I was looking for a similar problem but I did't find.

I have one raspberry pi 2 with ethernet port and wlan (via usb). I connect ethernet to lan network with access to internet and wireless to another local network with internet. The external IP's are diffrent. I would like to get remote access to raspberry form two internet connections at the same time.

Now i can connect to the first but now to second. When i change default gateway i can connect via second network but still not with one network in the same time.

My route looks like:


Anyone help me?

User avatar
Posts: 40193
Joined: Sun Jun 16, 2013 11:19 pm
Location: A small cave in deepest darkest Basingstoke, UK
Contact: Website Twitter

Re: Two internet connections

Fri Jun 29, 2018 3:57 pm

The gateway has a lower metric value so the kernel will always pick that ahead of the gateway. It gets a lower metric because eth0 is usually faster than wlan0.
Criticising any questions is banned on this forum.

Any DMs sent on Twitter will be answered next month.
All fake doctors are on my foes list.

Note: Any requirement to use a crystal ball or mind reading will result in me ignoring your question.

Posts: 295
Joined: Fri Aug 03, 2012 5:25 pm
Location: Brazil

Re: Two internet connections

Fri Jun 29, 2018 5:22 pm

For output connection route metric and routing table are enough.
But, for input, can have a problem, connection from second interface return using same routing decision as output, on most case client reject the connection assuming that is a spoofed connection. Or redirection just not work.
To solve it is necessary to ensure that connection coming from a interface return from its self. Routing from source coming to rescue.
Assuming wlan0 as secondary connection. and as wlan0 ip.

Code: Select all

Name a routing table
# echo "201 wlan" >>/etc/iproute2/rt_tables
copy relevant routing from main to new table
# ip route add dev wlan0 proto kernel scope link src table wlan
# ip route add default via table wlan
Insert a source routing rule
# ip rule add from lookup table wlan
A trick, use  ip route show to list main routing table
You can copy a entire line to add command of ip route add
To list a routing tabel of wlan
# ip route show table wlan
To list routing rules
# ip rule list
Before change routing table, copy result of these tree commands.
traceroute -i eth0
traceroute -i wlan0

And repeat after changes.

Return to “Troubleshooting”