Skip to content
rhashemian's profile

New problem solver

 • 

12 Messages

Wed, May 20, 2020 9:00 AM

Difference between WAN IP Address and WAN Static IP Address?

when i look at my cable modem status page i see the below image. some octets X'ed for privacy.

why is the modem assigned 2 separate ip's? one is my static addr (173.) and other (73.) some random wan address.

i know i can remotely access the modem using the 73. wan address, but why is that even needed? why not just use the static ip 173. as the modem address with some random port, like 8800 for remote access? is it just to give the modem a separate dedicated ip in case someone uses the bridge mode? 

 

just curious about the dual ip / network setup.

 

image.png

Official Employee

 • 

348 Messages

1 y ago

Hi there, thanks so much for taking the time to reach out to the Digital Care Team here through the forums and we are sorry to see that you are having some issues with the gateway or have any questions. You have reached the right team to help make sure we get this taken care of.  Can you please send us a private message with your name, the full address, and the account number? 

New problem solver

 • 

12 Messages

1 y ago

thanks for the reply but this particular question isn't about an issue, just an inquiry to understand the need for dual ip addresses from different subnets in cable modems/gateways. that's all, no rush.

Official Employee

 • 

258 Messages

1 y ago

Thank you so much for your patience. To help understand the need for dual IP addresses on our gateway modems, I have included a link that will provide an overview. Please let me know if this helps.  https://comca.st/2XtzBP5

New Contributor

 • 

2 Messages

2 d ago

Comcast_Gabriel,

if he even knows how to find the answer didn't care enough about your question to even try to answer it. 

I have the same question.  The link he posted is generic quickstart FAQ stuff. His link vaguely touches on the Dual-Stack IP or 2 IP protocol versions in use in their network.  They are:

IP version 4 (the static address you paid for and the additional at least 3 more that Comcast wastes per-account to provide them...)

IP version 6 (created because the world has already run out of IPV4 addresses, presumably because Comcast blows 3 away to give you even 1 usable address, and AT&T runs CONNEXUS <<< "because it connects us, right?" >>> public IPV4 addresses to literally every single internal server chassis (its easier for the rows of NSA hardware that you aren't supposed to talk about even though its insanely expensive and if you build something you have to pay for it...) to read everything you do that way... ;) )

Here is how your IPV4 network works in the Comcast bubble:

x.y.z.0     - IPV4 Network address.  Because they have created you an entire public subnet, this defines the start of the address space.

x.y.z.1     - The first usable pubic IPv4 address in your subnet.

x.y.z.2-253  - However many additional usable addresses you are assigned by Comcast.

x.y.z.Gateway - Yet another costly IP address wasted for your assigned "subnet" to send traffic to and receive from.
x.y.z.BROADCAST!!! - The final IPv4 address in your range, which is required for IPv4 to be able to send BROADCAST messages, or messages across the network to all hosts at the same time.

I would also like to know why, if I have my own range of public IP addresses, and I have to sacrifice on of them to your gateway to pass traffic to Comcast which basically wastes a limited public address, which are finite and cost Comcast and its customers money!   Presumably this WAN gateway public IP address is the directly attached device that feeds and receives from your public IPv4 address space.

Another possible answer:

Because your cable network uses IPv6 to be able to address unlimited private devices, those devices used to have to hook to a telephone line or an IPv4 network to even be reachable from the provider offices, and you are reusing that work (thanks Openstack!) to blend your traditional IP stuff with the new IPv6 stuff, the second WAN address might be related to how they are being combined internally.

If it is, that's what your customer asked you for.  You. could at least read the question and answer to see if your answer even makes sense.  Another option would be to learn how this stuff works so you are actually qualified to give an answer...

If not please enlighten us because dual IPv4 gateways means you just don't have the DHCP capabilities to handle this many customers and its impossible the way you are segmented to run that many DHCP lease scopes for the IPv4 space.

Also, please stop turning off bridge mode on my modem to try and build a phone company using WAPs on the down-low without obtaining the proper permits and licenses. Your people are poorly trained, if at all and keep breaking my connections.

@Comcast_Gabriel, that is how you answer a customer's question once you find them the correct answer. ;)