Scenario 92 Answers

1 The original design required a fully meshed IBGP-4 network. This was calculated to mean 250 connections, which was deemed unacceptable because it would be too great of a drain on resources. Route reflectors are obviously the answer. Configure Router A to run BGP and as a route reflector to clients B and C.

router bgp 100

network 10.0.0.0

network 131.108.0.0

neighbor 10.10.10.10 remote-as 100

neighbor 10.10.10.10 route-reflector-client neighbor 10.10.8.9 remote-as 100

neighbor 10.10.8.9 remote-as 100 route-reflector-client

2 Configure routers B and C to run BGP as clients to Router A. Router B:

router bgp 100 network 10.0.0.0

neighbor 10.10.10.9 remote-as 100

Router C:

router bgp 100 network 10.0.0.0

neighbor 10.10.8.10 remote-as 100

3 Having configured the cluster, are any other tasks necessary?

Given that the route reflector is now forwarding the routes between B and C, the link between these routers is no longer necessary, and the BGP-4 link between them should be broken. This simply requires the removal of the neighbor statements that create the link on both routers B and C.

4 The company has decided in its early stages to require organizations connecting into them to use default routes. How would these routes be disseminated without the organization's autonomous system, and how would an interior router running only an IGP determine which path out of the routing domain to take if it had more than one connection?

The routers in the client organization do not need to run BGP-4. They simply need to configure a default route and propagate this into the routing domain, in accordance with the interior routing protocol that is being run.

If the autonomous system were multihomed into the Internet, there would be more than one default route propagated throughout the system. Any router within the autonomous system would determine the best path to the outside world by comparing the routing protocol metrics between the default routes. Thus, RIP would select the lowest hop count, EIGRP the lowest combination of bandwidth and delay, and OSPF the lowest cost.

5 Given that the use of a default route by the client organization gives its the least configuration power to manage and manipulate its traffic flow, how would the network administrator justify this simple approach?

The default route, while giving the least control over the connection to the Internet, is very robust in that it has no working parts to fail. Therefore, it requires very little CPU or memory. The lack of redistribution eliminates the possibility of routing loops, and no routing protocol running over the physical link to the Internet frees up bandwidth for data.

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