Forty routers, one cut cable
A big college has forty routers (devices that pass data on). A builder cuts one cable. Traffic must take another road.
With typed routes, a person has to find the fault and change many settings. That could take hours.
There is a better way: routers that talk to each other and fix the map themselves.
Key words
| Word | What it means |
|---|---|
| Router | a device that passes data between networks |
| Routing table | the list of routes a router knows |
| Static route | a route a person types in by hand |
| Dynamic routing | routers share routes with each other and update themselves |
| OSPF | a routing method where routers share the map of the network |
| Neighbour | a router joined directly to this router |
| Area | a group of routers that share one map in OSPF |
| Network | computers and devices joined so they can share data |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say when to use dynamic routing and I can configure OSPF on three routers and test it.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Worked example: static against dynamic
| Static route | Dynamic routing (OSPF) | |
|---|---|---|
| Who makes the route | A person, by hand | The routers, by talking |
| When a link fails | Stays wrong until a person fixes it | Routers find another road |
| Best for | Small networks and single links | Bigger networks with more than one road |
| Work to set up | One line per route, on every router | A few lines on each router, once |
| Risk | A typing mistake or a forgotten route | More to learn and more traffic between routers |
The cells students fill in are left blank in this preview.
Extra: The OSPF commands
The next part is an Extra. It shows what configuring a dynamic route looks like on a real router program.
On each router you turn OSPF on. Then you list the networks it should share, all in area 0. Area 0 is the one area a small network needs.
Extra: First, the ping fails
sudo ip netns exec h1 ping -c 1 -W 1 10.0.3.2A command for the lesson’s lab terminal. It is shown here and not run.