10-02-2012 04:41 PM
We just got comcast at work which replaced our verizon internet and phones. So far we love the system and it's way faster. Everything seems great.
I do need one thing though and I don't think customer support understood what I was asking.
We have about 15 computers in our offices give or take.
Here is how our office is "wired" right now.
We have the comcast "modem/router" which is the SMCD3G-CCR downstairs in room "A".
The SMCD3G connects to a Linksys wireless router via ethernet in room "A". That Linksys router connects upstairs into a 24 port DLINK switch in room "B". From that switch it goes into room "C" and connects to an 8 port netgear switch which has 3 computers and a big xerox plotter printer (print system 510dp) connected to it..
My Xerox plotter is connected to an 8 port netgear switch in room C. In order for everything to work right that plotter needs a fixed ip address (I assume an interal ip address assigned by the comcast modem/router unit).
Right now I have the xerox plotter set to 10.1.10.63
I want to ensure that no other computers can get that IP address assigned to them.
After loggin into the router and looking all the computers are below 10.1.10.35 but I would just like to be able to set it up in the comcast SMCD3G that the address 10.1.10.63 cannot be assigned by DHCP. I have manually assigned it to the printer which I did by physically changing the settings on the printer and set it up on that IP address when I installed the driver on the windows 7 machines that will print to the plotter.
Is there any way I can do that? I basically want to have the peice of mind that the comcast modem/router will not assign the printers address of 10.1.10.63 to any of the office computers.
If I can do this, that should be something that I only have to do on the comcast box. I shouldn't have to do that on the Linksys router or mess with the two switches?
10-02-2012 05:03 PM
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10-02-2012 08:49 PM
there is a little more info i need. the ip address for the printer indicates that dhcp server is the comcast modem, not the linksys router. what model is the linksys?
default ip for comcast smc is 10.1.10.1
default ip for linksys router is 192.168.1.1
are you sure that all devices and switches are behind the linksys router?
by assigning the dhcp range to be x.x.x.100 to .150, you will ensure that no machine will take x.x.x.63
hope this helps,
10-03-2012 08:11 AM
that is correct. The comcast smc device feeds into the linksys router. Every other computer gets internet either directly via the linksys router or via one of the two switches. Nothing ties directly into the comcast smc besides the linksys wireless router.
I'll look up the model of it.
I know our "network" has a default gateway of 10.1.10.1 as if I do an ipconfig on any computer it tells me that.
10-03-2012 11:01 AM
This does not answer your question directly but by having the Linksys router connected to the SMC gateway device you are cascading two routing devices and introducing a double NAT condition. If you wish to keep this config the way it is then call in and have them place the SMC in to "bridge mode" so that it acts as a plain vanilla cable modem with no routing function. You are currently using it in such a fashion anyway.
10-03-2012 01:51 PM
I'm not exactly sure what you mean by "double NAT".
I think the comcast SMCD3G unit is doing all the routing?
The linksys would use something like 192.168.1.1 wouldn't it ?
I think the comcast default gateway for this device is 10.1.10.1
How do I tell if both devices are "routing" ? I'm not sure but like I said
I think the SMC is doing it now.
10-03-2012 02:51 PM
If you have the 'Internet' port of the Linksys router connected to one of the LAN ports of the SMC, then you have two devices providing routing on your network. If your computers are connected to the Linksys router, the SMC router will not know how to get to the LAN network on the Linksys router, unless you have statically routed the Linksys LAN network on the SMC via the WAN IP address that the SMC is probably supplying the Linksys router.
In addition, the Linksys router most probably has a firewall active, which prevents traffic from the WAN network reaching the LAN devices, unless you set up port forwarding (or switch off the firewall).
10-04-2012 09:42 AM - edited 10-04-2012 11:00 AM
So the network looks like this:
------SMC ---------------> Dlink Switch -------------------------> Netgear Switch
- -----------------> Linksys wireless access point
10-04-2012 10:56 AM
Actually the Linksys device isn't even a router.... it's a wireless access point.
It's a Linksys WG602 v4 wireless access point.
So there is no double nat condition? Only one router which is the SMC
So back to my original issue:
In the SMC control panel I should be able to set the ranges that DHCP can assign?
So under the LAN sub catagorey, the first tab says IP Setup.
Under the IP Setup it says "Enable LAN DHCP" which is checked
Under that it says Lease Time: 1 Week
DHCP START IP: 10.1.10.10
DHCP END IP: 10.1.10.199
So if I change the DHCP START IP to 10.1.10.70 and leave DHCP END IP at 10.1.10.199 then the SMC should never "give out" the IP address I manually assigned to my router of 10.1.10.63 but all the computers should be able to print across the network to that computer correct? They will still be able to "reach" the printer on that IP even though I told the SMC not to "give it out" or assign it via DHCP in other words?
10-04-2012 12:18 PM
If you change the DHCP range on the SMC to one that excludes the IP you have assigned to the plotter, it should not give ou that IP to any other DHCP clients on the network.
You should also check to make sure that the WAP (which is a Netgear device, based on the model number, not Linksys) is not acting as a DHCP server also. I don't think it has that capability, but you should check.
10-05-2012 09:51 AM
I think my access point actually does have that capability (to act as a DHCP server).
I need to log into that wireless access point (which is a netgear unit) and then disable that. Since my SMC device is a router, the three computers using wireless will have no problems connecting to the network and the internet after I disable the DHCP server on the wireless access point right?
10-05-2012 10:55 AM
Right... the Netgear WAP should pass DHCP requests on to the network so an active DHCP server (in your router) can respond to them.
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