How do I configure a Sonicwall TZ210 to use a new CIDR block

Posted on 2011-09-15
Medium Priority
Last Modified: 2012-06-27
Hello everyone,

I currently have a sonicwall tz210 - SonicOS Enhanced , and have 8 static IP's assigned to us by Cox.  I have been nating to 6 inside hosts, mostly rdp, and one web server.  Everything worked fine untill Hurricane Irene.  Cox is now having issues with nating in our area.  They may not be able to fix it for a couple of weeks.

They suggested going to a CIDR block a /27.  Does anyone know if my sonicwall can handle this type of addressing, and if so the steps to configure it to duplicate my current functionality.  I'm not seeing anything in the documentation.

We work with the NFL, so busy season just turned on big time.  Definitely not the time to be making big changes.  Any help is GREATLY appreciated!
Question by:Frank Fratzke, CPA
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LVL 33

Expert Comment

ID: 36543824
Yes, it will handle it. On the WAN interface of your sonicwall, what is your subnet mask. To use a /27, change the mask to

Author Comment

by:Frank Fratzke, CPA
ID: 36545642
So basically what you are saying is all I need to do with the sonicwall config is change the subnet to 224 for a /27 ( or 240 for a /28) for my outside address, and then setup a nat route to the internal hosts just as I normally would.
LVL 33

Accepted Solution

digitap earned 1000 total points
ID: 36546155
Yes. Setting the subnet mask essentially tells the sonicwall what public IP addresses it has the authority to answer to. Once you set that, you can run the public server wizard (or modify existing NAT policies) to use a public IP address in that subnet mask range. The ISP knows you own those public IP addresses and can send that traffic on to your firewall knowing it will be routed properly from there.

What's your current mask, /24?

Author Closing Comment

by:Frank Fratzke, CPA
ID: 36548364
Thanks for your help!

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