Double NAT

Ofloo

It has been driving me insane the last few days, but here it is.

I've got a second cable modem with isp setup the isp for some reason doesn't want to provide bridge, they've setup NAT on the modem, I'm able to portforward dmz and stuff like that but that's it.

So what i did was i've setup the router with a static LAN IP 192.168.10.10 the modem is 192.168.10.1 and ofcrouse it has a wan IP and nat enabled, .. I've setup DMZ to 192.168.10.10 so you would expect that portforwards would work but for some reason they don't.

I've tried doing this with NAT 1:1 mapped 192.168.10.40 to 192.168.1.40, on my other router this works fine with real IP's however on the one with double NAT this doesn't work at all, ..

Anyone any Idea's, ..

when I nc -l <port>on the router I can nmap that port from the internet however if i portforward it or nat1:1 it doesn't work.

short:

ipalias or ip arp proxy
1:1 nat
portforward isp

doesn't work

dmz isp
portforward on pfsense

doesn't work

i've done a tcpdump all i can understand from it is that it stops at the 192.168.10.10 IP, which is the so called WAN IP</port>

johnpoz

And when your box your forwarding to answers.. What wan connection will it go out of - the normal wan, or this new double nat wan?

You need to make sure your outbound nat is setup to use the correct connection.

I would sniff on your lan interface to see that traffic is forwarded to your server, and the server answers.

Ofloo

I did but all stops at the router, .. if i make a socket on the router for instance

nc -l 5060 then i can connect to it, but if i add a rule then it doesn't, the strange thing i just discovered however is, that UDP does pass through? only TCP is having issues and yes it's a new pfsense box and modem, ..

and all outbound rules are on the WAN interface

WAN	 	127.0.0.0/8	*	*	500	WAN address	*	YES	 	
WAN	 	127.0.0.0/8	*	*	*	WAN address	*	NO	 	
WAN	 	192.168.1.0/24	*	*	500	WAN address	*	YES	 	
WAN	 	192.168.1.0/24	*	*	*	WAN address	*	NO

same for localhost ofcourse

johnpoz

"and all outbound rules are on the WAN interface"

Huh?? There is no outbound rules on the wan.. All rules in pfsense are INBOUND to the interface.. Other than floating rules.

Oh your outbound nat –- well how is that going to work?? If your traffic comes in in isp 2, and you send out the traffic in answer out isp 1?

Your going to need an outbound nat rule for the traffic to go back out the correct wan connection.

Ofloo

Could you provide a sample cause it doesn't really make sense what it is you're saying.

lets say i want to forward 5060, .. then i would make a forward rule however in the outbound what am i supposed to do there?

johnpoz

You need the nat to go out the interface you came in on.. You have 2 wan connections right..

Do you need a picture?? So something comes in wan2, and then when try to talk back it goes out wan1 how do you expect that to work?

2wan.png_thumb

Ofloo

actually I've got 4 connections and 2 pfsenses, .. the thing is one of 2 works kinda, it has also nat issues, with your post this makes sense, however the new pfsesne has is new and has only one wan for now, .. the point is that it is behind a nat enabled modem, I can't disable it since it's the isp who delivers it like this, ..

However I can setup portforwarding and dmz, which I did, on the new pfsense the one I'm having issues with, .. I can make a port listen nc -l 5060 for example and connect to it from the internet, however once i setup portforwarding on the pfsense box it self to forward that traffic to a IP within the lan it doesn't work.

so basicly I can connect to the port however once I want to forward it, it doesn't work. So i think something is wrong in the NAT of the new pfsense, …

so basicly this pfsense has wan IP 192.168.10.10 and I need to forward some ports to 192.168.1.40 all the traffic arrives only at the point of portforwarding it all goes wrong but i can't wrap my head arround it why.

This is a forward, what would the corresponding outbound rule be.

WAN	TCP/UDP	*	*	WAN address	5060 (SIP)	192.168.1.40	5060 (SIP)

I thought these where those rules

WAN	 	192.168.1.0/24	*	*	500	WAN address	*	YES
WAN	 	192.168.1.0/24	*	*	*	WAN address	*	NO

Derelict

You do not need outbound rules with only 1 WAN/default gateway. pfSense is stateful.

Reworded: The default rules are all you need.

What's the corresponding firewall rule on WAN?

Ofloo

Euhm, I allow all traffic there's no rules needed, I guess I don't filter anything at this point.

Edit:

I need to verify something, .. maybe I thought of the reason, .. but not sure if this could be the cause. As i said I have 2 pfsenses

WAN => pfsense1 => 192.168.1.1/24
WAN => pfsense2 => 192.168.1.2/24

the pfsense1 does nat on that range and pfsense2 as well is and forwards traffic to the same range is that possible.

Derelict

No rules means no connections allowed into WAN.

Ofloo

No I have rules but allow any.

IPv4 *	*	*	*	*	*	none
IPv6 *	*	*	*	*	*	none

So I don't really see the point in adding an extra rule, that specifically allows that traffic, because allow any should match all.

Derelict

No that's fine. You'll have to figure out where the breakdown is then. Check everything on the inside client (like its default gateway, firewall, etc.)

Ofloo

ok the idea is to add a sip trunk and backup sip trunk to have one go over one wan and the other over an other wan

so basicly i forward the port 5060 to 192.168.1.40 on both pfsense, the gateway for the 192.168.1.40 is 192.168.1.1, however on the pfsense1 box I have a rule that when it matches the target IP it should use the pfsense2 as gateway so this should be fine.

pfsense1 forward 5060 to 192.168.1.40
pfsense1 if target IP 91.213.251.136 and dport 5060 make it use gateway 192.168.1.2 otherwise gateway 192.168.1.1
pfsense2 forward 5060 to 192.168.1.40

and finaly on both the same nat rules as above. I can reach the traffic up until pfsense2, so if i remove the forward rule and setup nc to listen on 5060 i can connect to it and send and receive data, however for some reason it doesn't want to forward that traffic to the 192.168.1.40

Derelict

I can't decipher that. Draw a diagram. See the one in my sig for the type of information you should include.

Ofloo

I understand, .. can you recommend a unix/linux program to do so.

marcelloc

Sip/rtp will not work with double nat. You will need a sip server or a sip and rtp proxy on the firewall(or beside) to workaround it.

Derelict

It's hard enough with single NAT/PAT.

For future reference:

Free Diagramming Software: https://forum.pfsense.org/index.php?topic=1630.0

Ofloo

That's the whole point SIP does work but it uses UDP, I wanted to give clients access to it using TCP cause in some networks UDP can't get passed a proxy, you need TCP but sip does work when it's using UDP it uses the same rules as TCP but for some reason TCP doesn't work.

And I have a sip server

johnpoz

"You do not need outbound rules with only 1 WAN/default gateway. pfSense is stateful."

Agreed.. But from his first few statements..
"I've got a second cable modem with isp setup the isp for some reason doesn't want to provide bridge"

But seems he using a different copy of pfsense, which is my bad for not reading it correctly. But which is why I asked if 2 wan connections.
"You have 2 wan connections right.."
" What wan connection will it go out of - the normal wan, or this new double nat wan?"
"If your traffic comes in in isp 2, and you send out the traffic in answer out isp 1?"

Ofloo

double, still working on that network map, have it ready in a bit