The de-facto Enterprise fiber setup from Comcast is to assign a single /30 address. If you need additional addresses, they will assign them to you but you have to route them yourself unless you spring for the optional managed router.

In this exercise, I will show you how to load the addresses on to a Sonicwall gen7 series router so you can route a block of static IPs and save yourself the managed router cost. We are going to assume that X1 is the WAN interface for the Sonicwall router and you are using a /29 which has 6 addresses in the range: 5 usable and one for the gateway.

When requesting a block of static IPs, Comcast will give you a datasheet that shows a  /29 Customer LAN and a /30 WAN block.


The Comcast order will show a block address (the network address) and a usable address range. You will see 6 usable addresses in the usable block of a /29 but that’s because you have to set one aside as the default gateway. In this example, we will use the first usable as the default gateway which leaves us with 5 usable addresses for public access.

Configure the /30 address on the Sonicwall’s X1 WAN interface as shown below.


Next, navigate to network –> address objects and configure the /29 subnet as a network address object. The first address is the block address (network address) and it will be entered as the network address as shown below.


Next, assign an empty interface port the default DMZ zone (or create your own zone) and add the first IP address in the usable range (which will be the default gateway) and the appropriate subnet mask.


Go to policy –> access rules and create and ingress and egress rule.


Create a rule from WAN –> DMZ and another from DMZ –> WAN

If you don’t want any ports blocked set any to any allow. This will allow all traffic to flow to your /29 assigned devices.

Finally, connect a L2 switch to the interface and use it to connect devices that use static WAN IP from the /29 WAN subnet that was assigned to you. Your network setup should look something like this.



Note that the single static on the /30 WAN interface X1 is still usable in additional to the 5 usable addresses in your /29 network.

Leave a comment

Your email address will not be published. Required fields are marked *

error: Sorry, copy/paste is disabled
Skip to content