Comcast Multiple IP Question

Smiley · 11-21-2007, 12:52 PM

Has anyone every had multiple IP addresses from Comcast?

I'm wondering if they somehow assign two addresses through one cable modem or if they actually have you use two separate modems.

If it is separate modems, do you get your "full" bandwidth per modem connection?

Mac · 11-21-2007, 01:29 PM

basic network experience dictates to me that Comcast will give you multi Ip through same cable modem.

Would be based on MAC addresses... The example is anytime you change or switch a machine that in on a cable modem it gives the ISP your one allocated MAC address. When you buy additional IP's they make your MAC pool Higher say depending on how many you buy. Honestly, it comes down to what you need. Is the extra money worth what you can do for free on a NAT'd Network?

this isnt exactly what you asked but is pretty much going to cover a general base. Since thats how most ISP will run their networks. It would cost to much for ISP to have you use two cable modems rather its easier for them to use TCP/IP protocol to handle it through 1 cable modem.

Can't say to much but with a little snooping.. you can actually login to your cable modem and find out whats its doing.

Most of them are setup to use 192.168.100.1 try that in your web browser and see what shows up. Not all of them use this ip but I think over 70 % do

mimicvii · 11-21-2007, 02:56 PM

i don't know how it is now, but back in the old days with @home, you could have multiple static ip's behind one modem.

dudio · 11-21-2007, 04:14 PM

semi static, but in fact dynamic.

The local cable co's here provide up to 3 dynamic IP's with regular Hi-Speed service,
but only 1 IP with 'Hi-Speed Lite'.

Soul · 11-21-2007, 04:27 PM

I have 5 and they all come through the same modem, but I don't use comcast so it could be different.

Smiley · 11-21-2007, 04:35 PM

Soul, could you try a concurrent speedtest with a few systems on separate IPs and see how it compares to just running one separately?

I'm curious if all your bandwidth is rated as one for concurrent connections. Since they all come through the same modem then I suspect bandwidth is per modem MAC address, not IP or device MAC address.

My Comcast connection is starting to suck. I pay for 8M/768k and normally only can get 1.5M/348k. The next lan party would have very little shared bandwidth for attendees at this rate

{OF}Blong · 11-21-2007, 10:16 PM

Quote:

Originally Posted by Smiley

Soul, could you try a concurrent speedtest with a few systems on separate IPs and see how it compares to just running one separately?

I'm curious if all your bandwidth is rated as one for concurrent connections. Since they all come through the same modem then I suspect bandwidth is per modem MAC address, not IP or device MAC address.

My Comcast connection is starting to suck. I pay for 8M/768k and normally only can get 1.5M/348k. The next lan party would have very little shared bandwidth for attendees at this rate

very odd. i know comcast just implimented some hardware based systems that limit peoples bandwidth if they go over a certain amount in a month but they also basically shut down your bandwidth for torrenting (I know you dont use torrents so thats not a problem lol). Smiley have you looked into FIOS? i know its available less than 10 miles from my house so I would think it should be available to you though seems verizon is skipping the big cities and doing the small towns first.... I know with my charter I get 10/1 even though I am paying for 3/128. They never downgraded my connection only the price I pay

.
http://www22.verizon.com/content/consumerfios/

*edit nevermind its not available for you. i just looked it up and at least it gives you the form to fill out to be notified when it becomes available. When I do my address it tells me I have to call their office to find out.

{DvT}JonahHex · 11-21-2007, 10:21 PM

In terms of my understanding of cable internet technology...everyone in a "neighborhood" shares a given amount of bandwidth...I would expect multiple IPs in the same house (single or multiple modems) to affect each other in the same way that your neighbors' usage affects your available bandwidth.

If there is little traffic in the neighborhood during a concurrent test of multiple IPs, it is unlikely that you will notice any serious effects. If there is a lot of neighborhood traffic during the test, both will add to the bandwidth congestion.

Soul · 11-21-2007, 10:22 PM

My package is 15/2, and it is all encompassing, the IP's just act as shared.

LoPo · 11-21-2007, 11:17 PM

Quote:

Originally Posted by Smiley

I'm curious if all your bandwidth is rated as one for concurrent connections. Since they all come through the same modem then I suspect bandwidth is per modem MAC address, not IP or device MAC address.

This is generally how all ISP's handle it. You can have an entire class C, but your connection is still handled by the single modem, so you could have 254 IP'd devices sharing the same bandwidth.

Honestly if you're paying for 8Mb and only gettiing 1.5Mb I'd call and scream.