Cable/DSL Cisco Router Setup
In preparation of our CCNA exam, we want to make sure we cover the various concepts that we could see on our Cisco CCNA exam. So to assist you, below we will discuss Configuring a Cisco Cable/DSL modem router.
I want to first mention that this lab does not have the level of detail my other lab examples have on my site or the labs in the CCNA Lab Workbook. So please view the other labs examples we have on our site to get a full appreciation of the level of detail you will find in our CCNA Lab Workbook. The other lab examples are full blown labs whereas this is a quick configuration because we get so many questions on this topic and I wanted to post something on our site. We do have three full blown NAT/PAT labs in our lab workbook with extensive detail in them if you care to look at going the CCNA Lab Workbook route.
Ok, so you have been playing around with your Cisco routers and now you really want to play around with your home network and Internet connection. First and foremost I usually warn people about doing this in the first few weeks of their Cisco CCNA certification training. Think about it this way…you don’t really know that much if you just cracked open your Cisco CCNA study guide and now you want to “learn” how to setup a Cisco 2514, Cisco 2611, Cisco 2621(or any Cisco dual Ethernet router) up as your Cable/DSL router so you can do all the neat things like restrict traffic and such.
Great idea until you totally mess it up, have no idea what you are doing or how to fix it while your spouse, kids, parents, whomever are yelling at you because they can’t get to their myspace account….or worse yet, now you can’t get your home network back working to the point where you can get to some of your favorite websites or email accounts.
Ok, so enough about the warnings and sarcasm. Just let me be clear, you really should be through your Cisco CCNA study guide at least once before you try this so you can really understand and troubleshoot what you are doing if you have an issue. I mean is it really useful if you follow my instructions but don’t really understand what we are doing or why? That is why I suggest you wait until you get through your CCNA study guide at least once. Then go for it!
It seems that now days almost all high speed connects whether they are Cable or DSL internet connections use DHCP to provide the Public IP address to the customer’s router. So since that is the general rule, we will configure a Cisco 2611 router as a Cable router for my internet connection which at this time is Time Warner Cable. But this example should apply pretty much to any Cisco router that is dual Ethernet and to any Internet Service Provider that is using DHCP. Now you may ask why did I use a Cisco 2611 router as my Cable modem router? Well I really could have picked any Cisco dual Ethernet router as noted above. But I don’t care for the Cisco 2514 as a Cable/DSL modem router as you have to use transceivers. And I just have this bad habit of always knocking the transceivers off. I like the Cisco 2611 as it has dual 10mb Ethernet ports which works just fine for most Cable and DSL connections that don’t exceed 10mb(it is also currently a very economical solution compared to the dual 100mb routers). For the few that get the boost service of 30mb, well maybe you upgrade to a dual 100mb Ethernet router such as the 2621, 2611XM, 2621XM or one such as a 3640 with dual 100mb Ethernet modules in it. Ok, now that we got the hardware out of the way, let’s go over a few of the other assumptions we will make about the environment we are configuring.
1) You have a modem that is supplied by your ISP provider. You will connect a patch cable from the ISP supplied modem to e0/0 on our 2611 router.
2) Your Internet Service Provider is using DHCP to provide you with your Public IP address.
3) We will use PAT/NAT on the 2611 to do the translation of the internal private IP addresses to the Internet Service Provider public IP address.
4) We will also setup your 2611 to act as a DHCP server for your internal private computers and setup and exclusion or two.
5) The internal private IP address subnet will be 192.168.1.0/24 which consists of 192.168.1.1 to 192.168.1.254.
6) We will exclude from that range the 2611’s Ethernet interface of 192.168.1.1 which will act as the default-gateway for all your internal private clients and 192.168.1.98 which I so happened to configure statically for a host on my network.
7) Your DHCP server(your Cisco 2611 router), will also automatically assign two DNS server IP addresses to your DHCP clients. You will need to know the DNS server IP addresses your Internet Service Provider uses to configure this step. You can ask your Internet Service Provider or more easily see them in the configuration of your current Cable/DSL router.
8) When you private clients access resources on the Internet, it will appear that they are using the Public IP address assigned via your Internet Service Provider.
Now on to my running-config file. Just copy this configuration file into your Cisco 2611 router and you will be ready to go! As a side note, don’t forget to perform a “copy run start” so you don’t loose it up reboot. Additionally, you may need to shut off your Cable/DSL modem provided by your Internet Service Provider, wait about 20 seconds and then turn it back on while the 2611 is fully booted. Then wait about another 20 seconds and you should see a message flash across the console session about it just received an IP address via DHCP-ADDRESS_ASSIGN!
**Note: Don’t forget to run the “no shut” commands on each Ethernet interface.
service timestamps debug datetime msec
service timestamps log uptime datetime msec
no service password-encryption
hostname Cable Router
no aaa new model
ip dhcp excluded-address 192.168.1.1 (Router internal Ethernet interface)
ip dhcp excluded-address 192.168.1.98 (A server on my private network)
ip dhcp pool insideDHCP
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1 (Router internal Ethernet interface)
dns-server 126.96.36.199 188.8.131.52 184.108.40.206(you may need to change your DNS Servers here)
description External Ethernet Interface to the Internet
ip address dhcp
ip nat outside
no ip route-cache
no ip mroute-cache
description Internal Ethernet Interface for private clients
ip address 192.168.1.1 255.255.255.0
ip nat inside
no ip route-cache
no ip mroute-cache
no ip address
no ip address
ip nat inside source list 1 interface Ethernet0/0 overload
ip http server
access-list 1 permit 192.168.1.0 0.0.0.255
line con 0
line aux 0
line vty 0 4
I hope your found this article to be of use and it helps you prepare for your Cisco CCNA certification. I am sure you will quickly find out that hands-on real world experience is the best way to cement the CCNA concepts in your head to help you pass your CCNA exam!