How to configure office network with (1) Comcast modem/router; (2) wired switch; (3) wireless router

[ryams27]

Hey guys,

Let me preface by saying that I am by no means an IT expert and my situation is a bit strange, but I'll try to be as clear as I can.

Here's my situation:

I have the following hardware: (1) a business-class Comcast modem and 4-port router in one; (2) a TRENDNet 16-port gigabit switch; and (3) a Medialink wireless router.

My current setup is as follows: the Comcast modem/router has DHCP turned on and all four LAN ports are running into the TRENDNet switch, which in turn is connected to the various PCs and printers throughout the office. There is also an ethernet cable running from the switch to one of the LAN ports of the Medialink wireless router.

This is not the way I initially attempted to configure the setup, but this was the only way I could get everything to function properly. However, I have a feeling this isn't how it's supposed to be set up.

What prompted this post is that I'm having some issues with mobile devices staying connected to the wireless network. After doing some research, I believe it may be due to the authentication being set to AES instead of TKIP. However, I can't login to the Medialink router to change this because it apparently is sharing the same IP address as the Comcast modem/router. I've also read that the modem and router sharing an IP address can cause performance issues.

Can someone offer some guidance on how my network should be configured so that all three devices work in harmony and I'm able to access my router settings? Thanks in advance for any help.

 

[christinebcw]

ISP's modem, first...
...then WiFi Router...

now, you need to cable-connect your PC to that Router as the only device, and configure that Router... (log in as the administrator, change the password, all other settings as directed by your company and/or ISP)...

After that Router is set up, power down everything.

Now, insert the Switch between the WiFi Router and your computer.

Power everything back up. Your basic config should look like

ISP Modem -> WiFi Router -> Switch -> all other PCs

 

[abailey]

I take it someone else configured your network? You really need to get an IT expert out to take a look. Running all four LAN ports from the router to a single switch is a highly unusual setup. In fact that would cause major problems in most situations unless you have VLAN's running. The way it is configured, the Medialink should not be sharing IP addresses with the Modem/Router.
Ok now if you did install this network and your switch is not a managed switch with VLAN,s then you need to do this:
Only connect one ethernet cable from the Comcast modem to the switch.
Go into the DHCP settings on the Comcast modem and make sure you are not using the entire range. You need to reserve some IP's for static configs. So lets say your Comcast modem has an IP of 192.168.0.1. Then make sure your DHCP is set for like 192.168.0.15 - 254. That way you will have 192.168.0.2 -14 to hand out (or whatever your IP scheme is).
Now if you can't get to the Medialink, temporarily unplug the Comcast router from your network and then try to get to the Medialink.
In the Medialink router give its LAN IP address a static number (like 192.168.0.2, of course using your network numbers).
Make sure your Medialink DHCP server is turned off.
Also in the Medialink, on the 2.4Ghz band, make sure you are only using either channel 1, 6, or 11. Also make sure the channel width on the 2.4Ghz band is set to 20Mhz.
Now plug the Comcast modem back in and see how things go.

 

[abailey]

ISP's modem, first...
...then WiFi Router...

now, you need to cable-connect your PC to that Router as the only device, and configure that Router... (log in as the administrator, change the password, all other settings as directed by your company and/or ISP)...

After that Router is set up, power down everything.

Now, insert the Switch between the WiFi Router and your computer.

Power everything back up. Your basic config should look like

ISP Modem -> WiFi Router -> Switch -> all other PCs

If you can wire it like this, that would be simpler for sure. If you cannot, and need to leave the Medialink where it is and use it as an access point, then see my post above.

 

[ryams27]

ISP's modem, first...
...then WiFi Router...

now, you need to cable-connect your PC to that Router as the only device, and configure that Router... (log in as the administrator, change the password, all other settings as directed by your company and/or ISP)...

After that Router is set up, power down everything.

Now, insert the Switch between the WiFi Router and your computer.

Power everything back up. Your basic config should look like

ISP Modem -> WiFi Router -> Switch -> all other PCs

Thanks. Should I disable DHCP on the modem/router and allow the wireless router to assign the IPs?

 

[christinebcw]

Uh - your ISP Modem is also the router? Uh... hmmm... (I neglected to read that so carefully!) OK, the First Router should handle all DHCP services - it has to handle some, so it should handle all. Then, disable DHCP on the 2nd router - the WiFi.

Do a search for 2nd Routers and DHCP setups.

 

[ryams27]

Uh - your ISP Modem is also the router? Uh... hmmm... (I neglected to read that so carefully!) OK, the First Router should handle all DHCP services - it has to handle some, so it should handle all. Then, disable DHCP on the 2nd router - the WiFi.

Do a search for 2nd Routers and DHCP setups.

Thanks for the replies. I've finally got everything working the way it should.

To answer an earlier question, I was not the one who originally set up the network (e.g., I didn't run all four lan ports from the Comcast gateway to the switch). I did, however, tinker with it when we got a new wireless modem. I attempted to set it up as modem/gateway--->router--->switch, but I could never get them to play nice together. I tried disabling DHCP on the Comcast gateway and letting the router assign the IPs, etc., but nothing seemed to work. So I went with a kind of jimmy-rigged setup that went modem/gateway---->switch---->router, which actually allowed all the devices to connect and see one another. But, of course, I couldn't login to the wireless router and change settings, etc., and it may have caused other network problems of which I was unaware.

In any case, what I had to do get everything to behave like it should in the modem--->router--->switch setup was to call Comcast and ask them to change the modem/gateway to "bridge mode". Apparently there is no way for the user to do this on his end -- you must call Comcast and have them make the change. Now the "gateway" is acting strictly as a modem, the Medialink router assigns the IP via DHCP and connects all devices through the switch. Hallelujah!

 

[comcastuser]

The Comcast modem/router/telephone unit is referred to as the Wireless Gateway
After connecting the devices with Ethernet cables (Wireless Gateway -> WiFi Router -> Switch -> only one PC), power on only the Wireless Gateway and the wired computer
1. Open your browser
2. In the address bar, type the IP address (10.0.0.1) and press enter
3. Enter your user name and password (default = admin and password), click log in
4. Click on enable bridge mode
5. Log out
6. Power on the other devices
7. Open a new browser window
8. In the address bar, type in the IP address for your router
9. Enter the user name and password for the router
10. Configure the wireless router. Minimally, change the user name and password
11. Connect your other PCs and printers by Ethernet cable or configure the PCs and printers to connect wirelessly to the network