Netgear C6900 High Speed Cable Modem Router User Manual

							Specify Internet Port Settings 
81  Nighthawk AC1900 WiFi Cable Modem Router
An example is Internet Relay Chat (IRC). Your computer connects to an IRC server at 
destination port 6667. The IRC server not only responds to your originating source port, but 
also sends an “identify” message to your computer on port 113. Using port triggering, you can 
tell the modem router, “When you initiate a session with destination port 6667, you must also 
allow incoming traffic on port 113 to reach the originating computer.” The following sequence 
shows the effects of the port triggering rule you have defined:
1. You open an IRC client program to start a chat session on your computer. 
2. Your IRC client composes a request message to an IRC server using a destination port 
number of 6667, the standard port number for an IRC server process. Your computer then 
sends this request message to your modem router.
3. Your modem router creates an entry in its internal session table describing this 
communication session between your computer and the IRC server. Your modem router 
stores the original information, performs Network Address Translation (NAT) on the source 
address and port, and sends this request message through the Internet to the IRC server. 
4. Noting your port triggering rule and observing the destination port number of 6667, your 
modem router creates another session entry to send any incoming port 113 traffic to your 
computer.
5. The IRC server sends a return message to your modem router using the NAT-assigned 
source port (for example, port 33333) as the destination port. The IRC server also sends an 
“identify” message to your modem router with destination port 113.
6. When your modem router receives the incoming message to destination port 33333, it 
checks its session table to see if a session is active for port number 33333. Finding an 
active session, the modem router restores the original address information replaced by NAT 
and sends this reply message to your computer.
7. When your modem router receives the incoming message to destination port 113, it checks 
its session table and finds an active session for port 113 associated with your computer. The 
modem router replaces the message’s destination IP address with your computer’s IP 
address and forwards the message to your computer.
8. When you finish your chat session, your modem router eventually senses a period of 
inactivity in the communications. The modem router then removes the session information 
from its session table, and incoming traffic is no longer accepted on port numbers 33333 or 
113. 
						

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8
8.   Troubleshooting
This chapter provides information to help you diagnose and solve problems you might have with 
your modem router. If you do not find the solution here, check the NETGEAR support site at 
http://support.netgear.com for product and contact information.
This chapter contains the following sections:
•Troubleshoot with the LEDs 
•Cannot Log In to the Modem Router 
•Changes Not Saved 
•Wireless Connectivity 
•Troubleshoot Your Network Using the Ping Utility  
						

							Troubleshooting 
83  Nighthawk AC1900 WiFi Cable Modem Router
Troubleshoot with the LEDs
You can use the LEDs on the front panel of the modem router for troubleshooting.
Power LED Is Off
•Make sure that the power adapter is securely connected to your modem router and 
securely connected to a working power outlet. 
•Check that you are using the power adapter that NETGEAR supplied for this product.
•If the problem persists, contact technical support for help at www.netgear.com/support.
LEDs Never Turn Off
When the modem router is turned on, the LEDs light for about 10 seconds and then turn off. 
If all the LEDs stay on, this indicates a fault within the modem router.
If all LEDs are still lit one minute after power-up, do the following:
•Cycle the power to see if the modem router recovers.
•Press and hold the Reset button to return the modem router to its factory settings. For 
more information, see 
Factory Settings on page 89.
If the error persists, you might have a hardware problem. Contact technical support at 
www.netgear.com/support.
Internet LED Is Off
If the Internet LED is off and the modem router is connected to the cable television cable, try 
the following:
•Make sure that the coaxial cable connections are secure at the modem router and at the 
wall jack.
•Make sure that your cable Internet provider provisioned your cable Internet service. Your 
provider can verify that the signal quality is good enough for modem router service.
•Remove any excessive splitters that on your cable line. Run a “home run” back to the 
point where the cable enters your home.
Troubleshoot the Cable Internet Connection
When your modem router cannot access the Internet and your Internet LED is on, register 
the cable MAC address or device MAC address of your modem router with your cable 
Internet provider. 
Additionally, check the setting for your computer’s TCP/IP gateway. It should be set to use 
the modem router. modem router. If your computer obtains its information from the modem 
router by DHCP, reboot the computer and verify the gateway address. 
						

							Troubleshooting 
84 Nighthawk AC1900 WiFi Cable Modem Router 
Cannot Log In to the Modem Router
If you are unable to log in to the modem router from a computer or WiFi device on your local 
network, check the following:
1. Make sure that you are connected to the modem router’s wired or WiFi network.
•For a wired Ethernet connection, make sure that the Ethernet connection is secure 
and the modem router is powered on (its Power LED is lit).
•For a WiFi connection, make sure that you selected the correct network.If you cannot 
find the WiFi network, make sure that the modem router is powered on (it’s Power 
LED is lit). If the modem router is powered on, someone might have turned off the 
SSID broadcast or the turned off the wireless radios. See 
Wireless Connectivity on 
page 85.
2. If you are connected to the modem router network, but the web browser does not display the 
login window, check the following:
•Make sure that your browser has Java, JavaScript, or ActiveX enabled. If you are 
using Internet Explorer, click the Refresh button to be sure that the Java applet is 
loaded.
•Try quitting the browser and launching it again.
3. If the browser displays the login window, but you cannot access the modem router, make 
sure that you are using the correct login information. 
The user name is admin, and Both are case-sensitive. Make sure that Caps Lock is off 
when you enter this information.
4. If you customized advanced home network settings such as the IP address scheme, check 
the following:
•Make sure that the IP address of your computer is on the same subnet as the modem 
router. If you are using the recommended addressing scheme, your computer’s 
address is in the range of 192.168.0.2 to 192.168.0.254. 
•If your computer’s IP address is shown as 169.254.x.x, recent versions of Windows 
and Mac OS generate and assign an IP address if the computer cannot reach a 
DHCP server. These autogenerated addresses are in the range of 169.254.x.x. If your 
IP address is in this range, check the connection from the computer to the modem 
router, and reboot your computer.
•If your modem router’s IP address was changed and you do not know the current IP 
address, clear the modem router’s configuration to factory defaults. This sets the 
modem router’s IP address to 192.168.0.1. For more information, see 
Factory 
Settings on page 89. 
						

							Troubleshooting 
85  Nighthawk AC1900 WiFi Cable Modem Router
Changes Not Saved
If the modem router does not save the changes you make in the modem router interface, 
check the following:
•When entering configuration settings, always click the Apply button before moving to 
another page or tab, or your changes are lost. 
•Click the Refresh or Reload button in the web browser. The changes might have 
occurred, but the old settings might be in the web browser’s cache.
Wireless Connectivity
If you are having trouble connecting wirelessly to the modem router, try to isolate the 
problem: 
•The computer or WiFi device that you are using does not find the WiFi network.
This can happen for the following reasons:
-Someone pressed the WiFi On/Off button on the modem router, which turned off the 
wireless radios.
Check the 2.4 GHz and 5 GHz LEDs on the front of the modem router. If they are off, 
press the WiFi On/Off button to turn the wireless radios back on. 
-Someone logged in to the modem router and disabled its wireless radios or set up a 
wireless schedule.
In this case, pressing the WiFi On/Off button does not turn the wireless radios back 
on. You must log in to enable the wireless radios. Use an Ethernet cable to for a wired 
connection to the modem router. Then log in and change the settings. For more 
information, see 
Control the Wireless Radios on page 51.
-Someone logged in to the modem router and disabled its SSID broadcast. Your 
wireless network is hidden and does not display in your wireless client’s scanning list. 
(By default, SSID broadcast is enabled.) 
To connect with WiFi, you must type the network SSID and password. For information 
about how to enable the SSID broadcast, see 
Specify Basic WiFi Settings on 
page 47.
•You can find the WiFi network, but you can’t connect. Check the following:
-Make sure that your computer or WiFi device supports the security that you are using 
for your wireless network (WPA or WPA2)?
-You are not sure what the WiFi password is.
The preset WiFi password is on the product label. If you changed it and do not 
remember the new password, you can use a wired Ethernet connection to log in to 
the modem router and view or change the WiFi password. For more information, see 
Change the WiFi Security Option on page 49 
						

							Troubleshooting 
86 Nighthawk AC1900 WiFi Cable Modem Router 
-The WiFi signal strength is weak in your location:
Is your modem router too far from your computer, or too close? Place your computer 
near the modem router, but at least 6 feet (1.8 meters) away, and see if the signal 
strength improves.
Check for sources of WiFi interference that might block the signal. See Position Your 
Modem Router on page 9.
Troubleshoot Your Network Using the Ping Utility
Most network devices and routers contain a ping utility that sends an echo request packet to 
the designated device. The device then responds with an echo reply. You can easily 
troubleshoot a network using the ping utility in your computer or workstation. 
Test the LAN Path to Your Modem Router
You can ping the modem router from your computer to verify that the LAN path to your 
modem router is set up correctly.
To ping the modem router from a Windows computer:
1. From the Windows toolbar, click Start and select Run.
2. In the field provided, type ping followed by the IP address of the modem router, as in this 
example:
ping www.routerlogin.net
3. Click the OK button.
You should see a message like this one:
Pinging  with 32 bytes of data
If the path is working, you see this message:
Reply from < IP address >: bytes=32 time=NN ms TTL=xxx
If the path is not working, you see this message:
Request timed out
If the path is not functioning correctly, you might have one of the following problems:
•Wrong physical connections
For a wired connection, make sure that the numbered LAN port LED is lit for the port to 
which you are connected.
Check that the appropriate LEDs are on for your network devices. If your modem router 
and computer are connected to a separate Ethernet switch, make sure that the link LEDs 
are lit for the switch ports that are connected to your computer and modem router.
•Wrong network configuration 
						

							Troubleshooting 
87  Nighthawk AC1900 WiFi Cable Modem Router
Verify that the Ethernet card driver software and TCP/IP software are both installed and 
configured on your computer. 
Verify that the IP address for your modem router and your computer are correct and that 
the addresses are on the same subnet.
Test the Path from Your Computer to a Remote Device
After verifying that the LAN path works correctly, test the path from your computer to a 
remote device.
1. From the Windows toolbar, click the Start button and select Run.
2. In the Windows Run window, type:
ping -n 10 
where  is the IP address of a remote device such as your ISP DNS server.
If the path is functioning correctly, messages like those shown in the previous section display.
If you do not receive replies, check the following:
•Check that your computer has the IP address of your modem router listed as the default 
gateway. If DHCP assigns the IP configuration of your computers, this information is not 
visible in your computer Network Control Panel. Verify that the IP address of the modem 
router is listed as the default gateway.
•Check to see that the network address of your computer (the portion of the IP address 
specified by the subnet mask) is different from the network address of the remote device.
•Check that your cable or DSL modem is connected and functioning.
•If your ISP assigned a host name to your computer, enter that host name as the account 
name in the Internet Setup page.
•Your ISP might be rejecting the Ethernet MAC addresses of all but one of your 
computers.
Many broadband ISPs restrict access by allowing traffic only from the MAC address of 
your broadband modem. Some ISPs additionally restrict access to the MAC address of a 
single computer connected to that modem. If so, configure your modem router to “clone” 
or “spoof” the MAC address from the authorized computer.  
						

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A
A.   Supplemental Information
This appendix covers the following topics: 
•Factory Settings 
•Technical Specifications  
						

							 Supplemental Information
89  Nighthawk AC1900 WiFi Cable Modem Router
Factory Settings
You can return the modem router to its factory settings. Use the end of a paper clip or a 
similar object to press and hold the Reset button on the back of the modem router for at least 
seven seconds. The modem router resets, and returns to the factory configuration settings 
shown in the following table.
Table 2.  Factory default settings  
FeatureDefault behavior
Modem router 
loginUser login URLwww.routerlogin.com or www.routerlogin.net
User name (case-sensitive)admin 
Login password (case-sensitive)password
Local network 
(LAN)LAN IP192.168.0.1
Subnet mask255.255.255.0
DHCP serverEnabled
DHCP range192.168.0.2 to 192.168.0.254
Time zonePacific time
DHCP starting IP addressConfigured by the Internet provider
DHCP ending IP address192.168.0.254
DMZDisabled
Time zoneAs per the ISP/MSO ToD (Time of Day) Configuration
Time zone adjusted for daylight 
savings timeAs per ISP/MSO ToD (time of Day) server configuration
SNMPEnabled
Cable modem 
FirewallInbound (communications coming 
in from the Internet)Disabled (except traffic on port 80, the HTTP port)
Outbound (communications going 
out to the Internet)Enabled (all)
WirelessWireless communicationEnabled
SSID nameSee the product label
SecurityWPA2-PSK (AES)
Broadcast SSIDEnabled 
						

							 Supplemental Information
90 Nighthawk AC1900 WiFi Cable Modem Router 
Wireless 
(continued)Country/regionUnited States
RF channel (2.4 GHz)Auto1
RF channel (5 GHz)CH 153 (or manually select Band I and 4 Channels)
Operating modeUp to 600 Mbps at 2.4 GHz, 1300 Mbps at 5 GHz
1. Maximum wireless signal rate derived from IEEE Standard 802.11 specifications. Actual throughput can vary. Network 
conditions and environmental factors, including volume of network traffic, building materials and construction, and network 
overhead, lower actual data throughput rate.
Table 2.  Factory default settings  (continued)
FeatureDefault behavior