Scenario 111 Answers

Offer some reasons why the routing protocol Enhanced IGRP has recently been implemented in the network, and give the reasons for its deployment in that particular area of the network.

Enhanced IGRP is being run across the Frame Relay WAN in areas where there are no client or server workstations. The network routers are all Cisco devices, which understand Enhanced IGRP.

Using Enhanced IGRP is far more efficient on a WAN because incremental updates can be sent across the limited bandwidth. In particular, if either AppleTalk or IPX is running at the access level, the routing updates can be sent in Enhanced IGRP, which gives far more control and flexibility because it is a new, more sophisticated, proprietary routing protocol.

The ISP has decided that the company should set a default route into its domain. Write out the commands that would configure the default route.

The configuration commands to establish a default route from the company's network to the ISP domain are as follows:

Router(config)# router eigrp 100 Router(config-router)# network Router(config-router)# network Router(config)# ip default network

The network command is also required for EIGRP to propagate the network in the updates.

3 Is the router connecting to the ISP the only router that needs configuration? If this is the case, explain the reasons for your decision. If other routers need configuration, write out the commands required, explain why they are needed, and tell where they would be applied.

The router connecting to the ISP is the only router that needs to be configured. The default route will be propagated to all the other EIGRP routers automatically. Although default routes redistributed into a RIP environment require that the ip classless command be configured, this is for routers that are downstream from the router that is dealing with the redistribution. Because the routers at the redistribution points will have routes redistributed into them by Enhanced IGRP, they will have no problem in the lookup.

4 The ISP router connecting into the company network will need static route(s) configured. Write out the commands to configure the router.

The configuration commands to establish static routes from the ISP domain into the company's network are as follows:

Router(config)# ip route

Router(config)# ip route

Router(config)# ip route

Router(config)# ip route

5 Will these routes need to be redistributed into the ISP domain? If the answer is yes, explain the reason for your decision, and then write out the configuration commands. If the answer is no, explain the reasons for your decision.

The static commands will need to be redistributed into the ISP domain. Static routes are not redistributed automatically. Static routes configured with the outgoing interface as opposed to the next-hop address are considered by the router to be directly connected.

The commands for redistribution of static routes are as follows:

Router(config)# Router EIGRP 100 Router(config)# redistribute static Router(config)# default-metric 10000 100 255 1 1500

6 Are filters required in this design? If so, state why, describe the type of filters required, and tell how and where they would be applied

Because there are no redundant paths in the redistribution between protocols, no filters are required in the configuration of the routers. There will be no feedback between the protocols.

Because there is no routing protocol running between the company and the ISP, there is no requirement for filters here, either. If any filters were required, they would be for internal security and traffic control, and would be typically configured on the access routers entering the Frame Relay cloud. There could also be some distribution lists at the distribution layer to limit connectivity among the different regions.

7 It has been suggested that Enhanced IGRP should be configured using summarization. If this plan were to be implemented, on which routers would it be configured, and why?

Summarization would be configured at the access level to limit the number of updates that need to traverse the WAN.

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