multiple public ips on same subnet to single private network

RouterOS Beginner Basics
1

I’ve got a pool of public IP’s from my cable ISP. However, I am not able to assign multiple IP’s to a single MAC address because of ISP rules.


I want to have a single public IP masqueraded for most internet traffic, but I want to be able to 1:1 nat one of my other public IP’s

this is how the network will appear

							Cable Modem
								|
					_______________________________
				WAN INTERFACE eth0		WAN INTERFACE eth1
				MASQUERADE				1:1 NAT
				XX.XX.XX.102/27			XX.XX.XX.103/27
					|						|
					______________________________
							LAN interface eth2
								10.0.0.1
							_______|_______
							24 port switch    
					________________|______________
					|				|					|
					users			users			1:1 NAT to eth1
															10.0.0.10

I have the masquerade, etc, all working properly. The problem I am running into is the second public interface. Once I enable that interface, I lose internet connectivity. I am not sure if it’s trying to loop traffic in between the two public interfaces, or what?

I tried setting up a virtual ethernet interface for the second public IP, but was unable to get that to function. I also tried bridging eth0 and eth1 together, but this also did not work. Every solution I’ve tried resulted in either none of the functionality that I wanted, or traffic no longer being routed.

I’m obviously missing something. Any help appreciated!

2

You don’t need the wan interface eth1 configuration. Without modification of routes and so on, it’s bound to break your internet connectivity if running.

http://www.mikrotik.com/testdocs/ros/3.0/qos/nat.php

Just run netmap with the range of IPs you want.

3

eneimi, the problem with that is this:

my ISP will only allow me to have one IP per mac address.

4

You mentioned that in your first post.

I’m not aware that netmap will use the mac of your router interface to identify all the lan computers!

Have you tried it?

5

I was faced with this challenge. My ISP was able to provide one of my IPs on a different subnet in the same cablemodem, allowing the setup you show. Some ISP companies can, like Mediacom :slight_smile: , and some can’t, like Cox Communications :frowning: .

ADD: If they are unable or unwilling to provide that service, it is not the end. I used two MT routers this week to get around a stubborn provider that could not provide different subnets, even in two cablemodems. It was one of the two companies I mentioned above.

6

Tim, Mediacom is my ISP, so I’ll see if they can do that for me :slight_smile: