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450 Chapter 6: Routing
Notice that the same subnet was used for all three virtual circuits; a full mesh of virtual circuits
was used and a single subnet was chosen rather than one subnet per virtual circuit.
Answers to Task 2 for Scenario 6-3
Task 2 for Scenario 6-3 asks you to describe the contents of the IGRP update from Raleigh, sent
out its virtual circuit to Mount Pilot. Notice that there are four routes in the routing table and
four routes in the routing update. Split horizon is disabled on serial interfaces using Frame
Relay as configured without subinterfaces. Split horizon is disabled by the IOS if using Frame
Relay multipoint subinterfaces as well. Therefore, all four routes in the IP routing table are
advertised in routing updates sent out Serial0.
Answers to Task 3 for Scenario 6-3
Mayberry still will have a route to 170.1.1.0/24, which is the subnet covering all the Frame
Relay interfaces in this scenario. Because only one VC went down and the other VC is still up,
it is reasonable to expect that the physical interface is still up. No subinterfaces are configured
in this scenario, so Mayberry still will have a connected route for each interface that's currently
up, including 170.1.1.0/24 on serial 0.
Answers to Scenario 6-4: IPX Examination
Refer back to the network illustrated in Figure 6-26 and the command output in Example 6-27,
Example 6-28, and Example 6-29 to establish the Scenario 6-4 design details and the context
of the answers to the four tasks for this scenario.
Answers to Task 1 for Scenario 6-4
Task 1 for Scenario 6-4 asks you to complete a table with all IPX network numbers filled in. In
addition, this task asks you to list the command(s) you use to find these network numbers. Table
6-39 provides the IPX network numbers for this scenario. In my opinion, the show ipx
VC between Mayberry and
Raleigh
255.255.255.0
170.1.1.0
170.1.1.255
VC between Mount Pilot
and Raleigh
255.255.255.0
170.1.1.0
170.1.1.255
Table 6-38
Subnets and Broadcast Addresses (Continued)
Location of Subnet
Geographically
Subnet Mask
Subnet Number
Subnet Broadcast
ch06.fm Page 450 Monday, March 20, 2000 5:11 PM