Note: The Clack implementations of RIP and OSPF intend
to demonstrate the high-level concepts of distance-vector (RIP) and link-state
(OSPF) protocols. As a result, they are greatly
simplified from the real protocol specifications.
Clack is not required to answer all of the following questions, but trying
out different scenarios will be helpful in confirming answers you are
unsure of. The following two topology files will load networks
that are running RIP or OSPF:
As described in student
resources , these files are loaded using
File->Open . To run two instances of Clack simultaneously, just
open two browser windows to the Clack url.
This problem explores the update behavior of distance-vector and link-state
protocols from the perspective of a single router R .
For the following scenarios, consider whether R
will "always", "never", or "sometimes" transmit routing data
as a result of a certain event in the network (all events are described relative
to R). Note that the "chain of events" leading to R
sending an update may involve a sequence of actions by other routers.
We are asking whether this stimulus will eventually result
in an update from that would not have otherwise been sent by R
had the stimulus not occurred.
For each scenario, assume that all routers are advertising reachability to all
locally connected subnets (including those between routers), that the
network is not partitioned at any point, and that R has at least two neighbors.
You can disable and enable links in Clack by double-clicking on them in
the network view (disabled links turn red). The ifconfig command line
program can also be used to bring links up or down, and change the link metric
for local links. For RIP and OSPF, the routing table views in the network
view shows additional routing specific information (e.g., the metric).
You should already be familiar with the "counting to infinity problem"
of distance-vector protocols like RIP. Given the Clack RIP topology,
choose a set of one or more links that if disabled would to lead to the counting
to infinity problem.
With this outage, for what prefix did the cost "count to infinity?"