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Port forwarding via 3G problem

Hello Experts,

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The system includes

Server
IP: 10.99.200.97
OS: Win2012R2

3G router (VPN SIM Card)
Interface ppp0 IP: 10.1.0.1
Interface usb0 IP: 192.168.1.1
OS: ARM Linux

Client PC
LAN IP: 192.168.1.100

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3 of them connect by

Server <---> 3G router <----> PC Client

#########################

The 3G Router is basic linux with nothing but iptables command. I tried several command option but did not work so far.

Such as,
/mnt/nand1-1/ap/iptables -t nat -A PREROUTING -p tcp -i ppp0 --dport 21 -j DNAT --to-destination 10.0.0.100:21

PS. PC client can Ping 3g Router IP: 10.1.0.1 but cannot Ping 10.99.200.97
Will you have any ideas?
Thank you.

David Vicente

hello there,
that's normal, you aren't getting public ip from your 3g access.
so you can't port forward :)
Usually 3g provider give private ip to the router which has the SIM card. and they do nat .

trazodone

ASKER

I agreed. Is it possible to NAT from LAN IP to WAN (ppp0).
At least 3G router can ping the server.

David Vicente

mmmmmm
let me see
there is something missing in your description
Are you sure the 3g router can ping the server and not something else?
try some traceroute from:
pc client to server
3g router to server
server to pc client
server to 3g router

Does your server know the route for your pc lan ip ?

ccomley

You need to get a 3G sim that has a real public IP address, or you're never going to be able to sort out inwards access. Most SIMs use a carrier-NAT service that you have no access to so can't map across.

trazodone

ASKER

Hello David,

I cannot test tracert right now but I can answer your question by trying to ping before

Server ping 3G router success
3G router ping PC client success
Server ping PC client success

PC client ping 3G router success
3G router ping server success
PC client ping server Failed

Thisvshould be some config to make PC client reaches server.

trazodone

ASKER

Additionally server's IP and PC client's IP are static. 3G's IP is dynamic.

trazodone

ASKER

Let me correct some point.

Server ping PC client is not tested but I success forward port 88 so server can see port 88 on PC client by 10.1.0.1:88 (forward using iptables)

Thanks

David Vicente

Interface ppp0 IP: 10.1.0.1 <=== it's private ip that means you can't see it from outside.
there is something you are not explaining there. is there a vpn between that 3g router and a router on server site?

trazodone

ASKER

Yes it is VPN making for my project. Not a conventional 3G SIM card

David Vicente

try a traceroute from pc client to server and server to pc client.

Server ping PC client is not tested but I success forward port 88 so server can see port 88 on PC client by 10.1.0.1:88 (forward using iptables) <=== did you test the port forwarding from your server side?

trazodone

ASKER

I didn't test port forward at server side. I have no idea on how to do it. I will try tracert tomorrow. Will go to bed now :) see you soon and thanks a lot for discussion.

Cheers

Duncan Roe

@trazadone: this looks like your previous question https://www.experts-exchange.com/questions/29021081/Allow-offline-access-point-to-have-internet.html
Having an external-facing network interface with a dynamic local IP address is completely normal, as I (hope I) explained in that Q.
You are still welcome to my scripts to implement this, just say if you would like me to post them.

trazodone

ASKER

Hello Duncan,

This is slightly different from my previous question. Regarding this question I need to FTP files from my laptop to server via port 21. Appreciate if you can share your script.

Thanks

David Vicente

Server ping 3G router success
3G router ping PC client success
Server ping PC client success

PC client ping 3G router success

3G router ping server success
PC client ping server Failed

is it possible for you to disable the firewall on pc client and server to test if it's not a firewall issue.
Can you try pinging the router on server side from pc client and 3g router as well ?

trazodone

ASKER

Firewall is disabled on both PC and Server

SOLUTION

David Vicente

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ASKER CERTIFIED SOLUTION

Duncan Roe

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