LINKSYS WIRELESS ROUTER

The Linksys wireless router is capable of handing out an IP address and subnet mask, as well as DNS and WINS server addresses, to DHCP clients. To set up the wireless router, you need to access the configuration interface using HTTP and a browser. The default IP address of most models is 192.168.1.1, but it can be changed to suit your needs. Perform the following steps to access the router and configure its DHCP server:

1. Connect your computer to the Linksys wireless router.

2. Open a command prompt. For example, choose Start Run, enter cmd, and click OK.

3. Enter the command ipconfig.

4. Note the IP address of the default gateway for the interface connected to the router.

5. Open your web browser.

6. Enter http://A.B.C.D into the address line, where A.B.C.D is the IP address of the

7. In the Connect To dialog, leave User Name blank and enter the password for your router. The default is admin.

8. The initial page displayed is the Basic Setup page under the Setup tab. This is where you configure the DHCP server settings. If you would like to alter the IP address of the router, do so in the Local IP Address field, as shown in the following graphic. If you change the address, save the change with the Save Settings button at the bottom of the page so the Starting IP Address field will reflect your change.

9. The Subnet Mask field should match the mask of the local subnet to which the router is attached.

10. DHCP Server should be set to Enable.

11. The starting IP address will begin with the same three octets as your local IP address. You can change the last octet to one of your choosing, but be careful to make sure it is within the same subnet as your local IP address, which is advertised to clients as the default gate- way, and make sure enough addresses are left afterward for the devices you expect to be on the local network, which you can limit with the Maximum Number Of DHCP Users field next.

12. Set the Maximum Number Of DHCP Users field to the maximum number of addresses

you wish to hand out. Setting this field too high increases the risk of unauthorized hackers getting onto your network.

13. The Client Lease Time option can be set as high as 9,999 minutes, which is just shy of 7 days. The default is 0, which corresponds to 1 day and is equivalent to a setting of 1,440.

14. Enter the addresses of up to three DNS servers and one WINS server in the appropriate

fields.

15. Click the Save Settings button at the bottom of the page to finalize your configuration, and then wait for the confirmation page to display.

16. Click the Continue button on the confirmation page to return to the configuration pages.

17. Close the router’s configuration window by exiting your browser.

DHCP Relay Agent on a Cisco Router

When you do not want to configure a Cisco router as a DHCP server, you can configure the router as a DHCP relay agent. A relay agent watches for the DHCPDISCOVER broadcast on the interface acting as the agent and forwards it as a unicast to a proper DHCP server, which could be anywhere in the internetwork. The DHCP server must have a scope or pool corre- sponding to the subnet in which the interface acting as relay agent resides. The DHCP server will mask this interface address with the masks in each pool until it has a complete configu- ration to assign to the client. Note that DHCP is not the only broadcast type that the relay agent supports. A number of set UDP-based broadcasts, such as DNS queries, in addition to

many others you can configure with the ip forward-protocol command, are supported by

this function.

The following procedure assumes there is a DHCP service running on the DNS server at 172.16.0.10 but the router is attached to the subnet 172.16.10.64/26 and must act as a relay agent for the DHCP requests the clients on that subnet submit:

1. Go to the interface attached to the subnet in need of DHCP services and place it in the subnet.

DHCP-Relay-Rtr(config)#int f0/0

2. On the same interface, which will have to watch for the DHCPDISCOVER broadcasts from the clients on that attached subnet, issue the ip helper-address command to give the router the DHCP server’s address to unicast to when it receives the requests. DHCP-Relay-Rtr(config-if)#ip helper-address 172.16.0.10

Note that you can configure more than one helper address on the interface, but the overall procedure is a very simple one to perform. If a DHCP server already exists on the internet- work, this may be the easiest solution to implement.

Criteria for Completion

You have completed this task when you have configured all addresses on all desired devices in the manner you wish to employ and tested for appropriate connectivity, using utilities such as ping and traceroute.