hmurchison
join:2009-04-09
Bothell, WA
| SB5120 issue. Guys/Gals tell me i'm not crazy Ok i've done some searching on this and I can't get the answer I need here. Here's my issue.
Basic Windows XP PC that was direct connected to the SB5120 and works like a charm.
Brought home a Mac Cube and Netgear GigE hub. Hooked everything up and set the Mac for DHCP. No go. Tried to renew the lease several times. Finally I got it on after releasing the IP from the PC and power cycling the SB5120.
I thought my problems were over and that I'd be able to get another IP for the PC but lo and behold the PC wouldn't connect and gave me a
"An error occured while renewing interface Local Area Connection: unable to contact your DHCP Server. Request has timed out"
So in a nutshell I've found that the SB5120 is leasing a workable IP address on a "first come first served" basis and locking the other computer out with a self assigned 169.254.x.x address which of course means no interweb.
Called Comcastic twice and was told "call Apple" to which I replied "why? I can get the Mac on ..just not at the same time as the PC" and vice versa and that I could only connect the Mac with an Airport (WTF?)
So my question to those who are so gracious to let me know their suggestions and/or experiences is this. Is there something I'm being ignorant of regarding the SB5120. Am I assuming that it should automatically lease out IP addresses to my PC and Mac?
SB5120 stats
Software Version -SB5120-2.19.0.12-SCM03-NOSH
Hardware Version: 4
MIB Version: II
GUI Version: 1.0
VxWorks Version: 5.4
I noticed that the IP address varied by what I consider an interesting amount. X denotes the same number.
Mac- x.227.293.33
PC- x.231.168.83
Both IP are consistent
Any suggestion will be greatly appreciated folks. I've got a 10yr old that is getting the Mac as a surprise and I want the net to work. | |
|
 
NoVA_CoxUser
Stand back from the cage -- The RF bites
Premium
join:2004-07-06
Alexandria, VA
 ·Cox HSI
4 edits | 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.  | |
|
 | hmurchison
join:2009-04-09
Bothell, WA
| Re: SB5120 issue. Guys/Gals tell me i'm not crazy 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. | |
|
| | ajwees41
Premium
join:2002-05-10
Omaha, NE | Re: SB5120 issue. Guys/Gals tell me i'm not crazy 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. | |
|
| | |
NoVA_CoxUser
Stand back from the cage -- The RF bites
Premium
join:2004-07-06
Alexandria, VA
·Cox HSI
| Re: SB5120 issue. Guys/Gals tell me i'm not crazy 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. | |
|
|
|
|
