NoVA_CoxUser
Stand back from the cage -- The RF bites
Premium
join:2004-07-06
Alexandria, VA
 ·Cox HSI
4 edits | reply to hmurchison
Re: SB5120 issue. Guys/Gals tell me i'm not crazy
First, your ISP generally only provides you w/ a single IP.
That IP is "linked" to the MAC of the device connected to the modem
Next, everytime a new device is connected to a cable modem (technically it's everytime a device w/ a different MAC is attached), the modem needs to be power-off reset.
Lastly, while the modem indeed contains a DHCP server, it ONLY issues short-lease IPs when the modem is offline (i.e. not connected to your ISP). This allows you to access the modem's dignostics pages.
Anytime your modem is "online" the modem's DHCP server is inactive and all IPs are issued by your ISP's DHCP server.
So ... if you change the device directly attached to your modem, you'll always need to reboot the modem.
Using a router prevents this; as the router is the one device always connected to the modem -- and it never
changes -- the modem doesn't require a reboot.
If you need more than one IP (and you do since you have more than one device) you'll need a router.
It's unfortunate that your ISP's "tech support" didn't seem to understand this basic element of cable modem operation.  |
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hmurchison
join:2009-04-09
Bothell, WA
| NoVA_CoxUser
Thanks for the response. I was thrown a bit because I have FIOS at home but the Actiontec CPE they use does routing and Wifi so it's as close to plug and play as possible.
Looks like I'll take a trip to Fry's and pick up a small router.
The Comcast reps I spoke to were a bit green but I figured some of the blame would be on my shoulders for assuming that a DHCP server would lease more than one IP without a router in the chain.
I'll call Comcast and see if they can swap the CPE with the models they use for home networking or buy a 3rd party
Many thanks and have a great weekend. |
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ajwees41
Premium
join:2002-05-10
Omaha, NE | What do you have at home comcast or FIOS?
Like Nova said you need a router or a switch and pay for a second ip if your are using comast. |
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NoVA_CoxUser
Stand back from the cage -- The RF bites
Premium
join:2004-07-06
Alexandria, VA
·Cox HSI
| said by ajwees41  :... you need a router or a switch and pay for a second ip if your are using comast. Not exactly ... he needs a router OR ELSE he'll need to pay Comcast for extra simultaneous IP addressses. |
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