Transparent NAT

RouterOS General
1

Good evening all, how are you doing ?

Here is my topology :
LTE MODEM <----> CCR 1036
LTE public IP: X.4.4.4 / ETHER1 IP : 192.168.1.1 ------------- ETHER1(WAN):192.168.1.2 / ROUTE+NAT / LAN BRIDGE: 10.0.0.1/8

I would like to know how can i link LTE to the CCR 1036 ETHER1 WAN transparently, because i don’t want to double NAT.
Basiquely the LTE interface forward everithing received to the ETHER1 of 1036, and vice versa ?

How would you do it ?
Thank you very much

2

Hey

two options:

  • lte passthrough
  • or just route (and don’t nat) traffic to lte modem. lte modem would need to know how to reach your internal network, so you’ll need to add route table entries for internal ranges.
3

Yes very good !

Passthrought i knew it :slight_smile:
and second option

  • or just route (and don’t nat) traffic to lte modem. lte modem would need to know how to reach your internal network, so you’ll need to add route table entries for internal ranges.

I don’t want to do that because i can expect lot of customers (more than 20000 devices), the LTE modem is a bit too weak for letting it doing that. i think it is better to try to do ANT on the CCR1036.
Any other idea ?

Thank you very much

4

Need NAT + LTE not enough for NAT → NAT somewhere else → pass-through is the ONLY option

5

okay i see.
Or any idea with netmap or srcnat/dstnat ?
Like it just translat the ip address but keep same src port and dst port ?

thank you

6

Most LTE modems playing smart by doing NAT themselves are not configurable enough to do netmap-style of NAT … even if they do, you should find a way to configure that on the LTE modem thingy, nothing to be done on RB. And since you want to perform NAT on CCR in a smart way, you can’t do netmap-style of NAT on CCR either.