Allowing internet access overt ppp0 from eth2

Question

So i'm trying to set up access over a hotspot to internet via a ppp0 interface (similar to a 4g dongle).

I've setup the default route with highest priority (Metric 1) for ppp0.

Set all iptable policies to ALLOW and enabled ip forwarding (as below) but I still cannot ping

ping -I eth2 8.8.8.8

Note that ping -I ppp0 8.8.8.8 works and also the default one (ping 8.8.8.8) goes over ppp0

Here is my configuration

# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.16.172.175   0.0.0.0         UG    1      0        0 ppp0
0.0.0.0         192.168.0.1     0.0.0.0         UG    10     0        0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
192.168.82.0    0.0.0.0         255.255.255.0   U     0      0        0 eth2

# cat /proc/sys/net/ipv4/ip_forward
1

iptables -F
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P POSTROUTING ACCEPT

Answer 1

Only the port forward is not enough.

The devices on your local wifi network have the IP 192.168.0.* . You set up them to forward to your router. Then your router forwards their packets to the Internet - without changing them.

The problem is that only your router knows, how to handle 192.168.0.*, because it is a local address space.

You need to set up your IP masquerading on your router. Essentially, it needs to alter the outgoing packets on a way, as if they would came from him, directly. Of course it needs to do the reverse to the incoming packets. More details can you read here.

Beside that, you need also a DHCP server for network autoconfiguration, and at least a local caching DNS server would be also useful.