Cisco Router & Cable Modem

Monday, 11 July 2011 21:46 Webadmin

Great Site - Cable Modem & Cisco Router

Good primer...


router> enable
router# configure terminal
router (config) # interface ethernet 0/0
router (config-if)# ip address dhcp
router (config-if)# no shutdown


router (config-if)# interface ethernet 0/1
router (config-if)# ip address
router (config-if)# no shutdown


router# show ip interface brief


router> enable
router# configure terminal
router (config)# ip dhcp excluded-address


router (config)# ip dhcp excluded-address


router> enable
router# configure terminal
router (config)# ip dhcp pool HOME_CLIENTS
router (dhcp-config)# network
router (dhcp-config)# default-router
router (dhcp-config)# import all


router (dhcp-config)# dns-server

The above command will send out DNS server address of and to the clients.


You can also configure the router to use the above DNS server using the following command in the global configuration mode:
router (config)# ip name-server


You need to remember three basic steps for configuring NAT/PAT:
  1. Create access list to decide which private IP addresses are allowed to be translated by the router.
  2. Issue the NAT command to cooperate NAT with access list that we created and tell the router that we need to overload the requests if you use PAT.
  3. Identify which interface in the router that is connected to the LAN then issue ip nat inside command, and which interface is connected to the internet then issue ip nat outside command.

The steps are not necessarily be in that order, we can start with whichever step first. Here how you do those steps:

Create Access List
router> enable
router# configure terminal
router (config)# access-list 101 permit ip any


router (config)# ip nat inside source list 101 interface Ethernet0/0 overload


router (config)# interface ethernet0/0
router (config-if)# ip nat outside
router (config-if)# interface ethernet0/1
router (config-if)# ip nat inside


router (config-if)# exit
router (config)# ip route ethernet0/0







Last Updated on Monday, 11 July 2011 22:02