Hi,
I have an issue with a packet tunnel that have two ipv4 networks. The first network works well but the second does not, because when trying to reach any IP of the second network, the source IP used is one of the first network.
Setup
So, I have a NE (Network Extension), with a packet tunnel. Internally our application create two tunnels to access different resources. These tunnels are linked to two local networks.
utun3 192.168.1.42/24 <===> tunnel 1
utun3 192.168.2.42/24 <===> tunnel 2
To clarify, I only have one NE, but two ipv4 network in it (configured via NEIPv4Settings)
I also configured routes to tell the NE that both networks whould go through the tunnel.
Problem and Investigations
Trying to ping 192.168.1.1 does work, however, trying to ping 192.168.2.1 does not.
Doing a bit of tcpdump on the interface shows that the source IP used is 192.168.1.42 instead of 192.168.2.42
Seeing that, I suspected some kind of routing issue, therefore I removed the routes from the NE and tried to add some by hand. I ended up adding the following :
192.168.1.0/24 via 192.168.1.42
192.168.2.0/24 via 192.168.2.42
With this it actually worked. Delighted by this quick resolution, I deleted any static route I had created, rushed back to my application and added theses routes into the NE.
And it did not worked.
Very surprised, I tried to find the difference between me adding the route manually with route add ... and the NE adding the route.
But it got much weirder, as netstat -rn showed me that the created routes where identical.
Digging through the internet I was unable to find many people with a similar issue. Also, I saw something about NE route and user added routes being different, but not many information, and not enough to help me out.
In the end, I started suspecting an issue with the Network Extension. Moreover since the API does allow to add multiple ipv4 networks.
Do you have any information on this topic ?