Original subtitles

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Now think of your router at home that gives you Internet connectivity

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in my example, I have a little British Telecom router

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that's connected to the Internet, this router doesn’t know about all the routes

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in the Internet because that is just too much for the router to handle

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so routers such as this have default gateways or default routes

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giving them access to the Internet, in the same way here

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I have the brand new Cisco router which I've connected to my Local Area Network.

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At the moment show ip route

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shows me no routes in the routing table

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because I haven’t configured any IP addresses on this router.

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show ip interface brief

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shows me that there are no IP address is configured

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on any interfaces on this router.

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So on F0/0 I’m going to configure

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an address of 192.168.1.128 as an example with /24 mask.

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That’s an IP address in the subnet used by my Internet gateway router

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I’m going to no shut the interface

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and then I’m going to test whether I can ping my VT router

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which gives me Internet access, as you can see the ping succeeds

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however, in the routing table, I only have that network

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I don’t have any other networks and I don’t have a gateway of a last resort set.

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So if I try and ping a website such as google.com

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it doesn’t work

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now that’s partly because I need to enable IP domain lookup

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and I need to tell it the DNS server that I’m going to be

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using in this case, I'll use Google, so when I try ping google.com

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it's trying to resolve that domain name with Google DNS servers

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but it’s going to timeout

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because this router doesn’t have any route in its routing table

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apart from the directly connected network 192.168.1.0

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so notice that times out, do show ip route again

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we only have that single route in the routing table

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so to solve this I can use the command IP route.

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now in this case rather than specifying the individual network

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I’m going to specify 4 0's 0.0.0.0 which is a default route

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subnet mask is going to be 4 0's as well

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I need to then specify my next hop router

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in this case, it’s my local BT internet router which is 192.168.1.254

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so show ip route

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my Cisco router only has this static route

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and a directly connected route in the routing table.

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show that again, there the 2 entries but notice the change

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gateway of last resort is 192.168.1.254

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in other words, to get to the default route my router can send traffic

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to this router, notice the little * which means candidate default route.

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so I’ve got static candidate default route

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because we've configured 0.0.0.0/0 via this IP address

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so can I now ping google.com? The answer is yes, I can.

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because this local router knows that to get to any network

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it needs to forward the traffic via this IP address.

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What about yahoo.com, that works, what about gmail.com, that works

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what about cisco.com that works

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so by using a single static route I can access networks on the Internet.

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now some websites as an example will deny ICMP messages

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so cnn.com is not allowing me to ping their website

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but I could telnet as an example to cnn.com on port 80

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and notice I’ve connected, it says it open, press enter

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how much is happening I'll press CTRL-C

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and notice I see a bunch of HTML text

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it's quite a bit information on the website

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but notice HML, so I managed to connect to cnn.com via HTTP

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because I have a static default route in the routers routing table

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forwarding traffic to a gateway of last resort.