Hi,

I’m no Shorewall expert, so please regard this answer as possibly 
incomplete. I think I can help you a little with the aliased configuration, 
not with the NAT part.

It’s important to understand that the aliased ‘interface’ actually isn’t a 
separate interface: eth0 and eth0:1 are regarded as the same thing. If you 
want to differentiate between them, you will have to specify an IP address 
in the SOURCE or DESTINATION column of the rules file. For example:

# Public interface
ACCEPT        net        $FW:12.34.56.78        icmp        echo-request
# Private interface
DROP           net        $FW:98.76.54.32        icmp        echo-request

It is possible to create variables to hold the IP addresses in the Shorewall 
params file, for example:

PUB_IP=12.34.56.78
PRV_IP=98.76.54.32

FW_PUB=fw:$PUB_IP
FW_PRV=fw:$PRV_IP

Then you could say:

ACCEPT        net        $FW_PUB        icmp       echo-request
DROP           net        $FW_PRV        icmp        echo-request

Note that the 'fw' zone is mentioned in the variable declarations. This 
should be the same name as the firewall zone declared in the zones file.

Hope this helps a little bit,

Sascha Sanches



From: Aaron St. Pierre
Sent: Saturday, June 09, 2012 4:31 AM
To: [email protected]
Subject: [Shorewall-users] Aliased interfaces proper setup

Hello,

I'm new to shorewall and new to the list. My question is related to aliased 
interface and the proper configuration of shorewall for my setup.

I currently have a VPS running at linode and it has the following 
configuration:

eth0 primary address is publicly routed
eth0:1 is a private address and internal only

What I'd like to do is:

- limit traffic from the Internet to the FW (which is standard and makes 
sense).

But I'd also like to

- limit traffic on the private aliased interface as there are other VPS's on 
that same network which have nothing to do with me. I want to limit traffic 
on the internal private network to only the VPS's that I own and no others.

I've played around with a few different configurations, but really don't 
think I'm understanding what needs to happen here with respect to shorewall. 
From a firewall perspective it would seem simple enough to only allow 
traffic between my VPS's on the backend network but I'm not having luck 
translating that...

Currently I've got a one-to-one NAT setup from my Internet IP to the private 
IP. This is working great but I'm not sure what to do next.

Was wondering is someone could point me in the right direction. I'd send my 
configuration but there really isn't much to it. Like I said I'm using a 
basic configuration to do NAT and have three zones setup: fw, loc, and net. 
I've RTFM, esp the aliased interfaces page but still don't think I've 
grokked how to setup the rules.

Thanks for the help!

-- 

Aaron

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Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
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