Scenarios

The following scenarios and questions are designed to draw together the content of the chapter and to exercise your understanding of the concepts. There is not necessarily a right answer. The thought process and practice in manipulating the concepts are the goals of this section. The answers to the scenario questions are found at the end of this chapter.

Scenario 10-1

The ISP Flying Data has recently converted from OSPF to Integrated IS-IS. The migration was relatively painless. The company uses the private network 10.0.0.0 for IP and the private ISO addressing with AFI 49. They created a hierarchical addressing structure. Figure 10-7 illustrates this addressing scheme.

Figure 10-7. Diagram for Scenario 10-1

[View full size image]

The addressing of the network was a large project, with all the pitfalls that accompany such a major exercise. The network is now stable, and it is time to configure the WAN connections using multipoint Frame Relay, as follows:

1.	Issue the commands that will allow Router A to use IS-IS routing across the NBMA cloud as a broadcast medium. Refer to Figure 10-7 for the addressing scheme.

2.	The WAN is Frame Relay, and Router G has a point-to-point link with Router C. Issue the commands that configure Router C's link for IS-IS as a point-to-point link.
3.	To reduce bandwidth consumption and to hide some network detail, summarization has been suggested. Issue the commands for Router A that will summarize the networks with a prefix of /16 across the WAN.

Scenario 10-2

Given the configuration of IS-IS in Example 10-14, perform the tasks and answer the questions listed. The WAN has light user traffic and has a fully meshed configuration, as shown in Figure 10-8.

Figure 10-8. Diagram for Scenario 10-2

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Example 10-14. Router B's Configuration File

Code View:

RouterB#show running config
...
hostname B
!
clns routing
!
Interface Ethernet0
 ip address 140.100.104.1 255.255.255.0
 ip router isis
!
Interface Serial0
 no ip address
 encapsulation frame-relay
 clockrate 56000
!
Interface Serial0.2 point-to-point
 ip address 140.100.32.2 255.255.255.0
 ip router isis
 frame-relay interface-dlci 931
!
Interface Serial0.3 point-to-point
 ip address 140.100.16.2 255.255.255.0
 ip router isis
 frame-relay interface-dlci 631
!
router isis
 net 49.0002.0000.0000.000b.00
B# show clns interface
Ethernet0 is up, line protocol is up
  Checksums enabled, MTU 1497, Encapsulation SAP
  ERPDUs enabled, min. interval 10 msec.
  RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
  Congestion Experienced bit set at 4 packets
  CLNS fast switching enabled
  CLNS SSE switching disabled
  DEC compatibility mode OFF for this interface
  Next ESH/ISH in 15 seconds
  Routing Protocol: IS-IS
    Circuit Type: level-1-2
    Interface number 0x0, local circuit ID 0x1
    Level-1 Metric: 10, Priority: 64, Circuit ID: 0000.0000.000B.01
    Number of active level-1 adjacencies: 1
    Level-2 Metric: 10, Priority: 64, Circuit ID: 0000.0000.000B.01
    Number of active level-2 adjacencies: 1
    Next IS-IS LAN Level-1 Hello in 678 milliseconds
    Next IS-IS LAN Level-2 Hello in 1 seconds
Serial0 is up, line protocol is up
  CLNS protocol processing disabled
Serial0.1 is up, line protocol is up
 CLNS protocol processing disabled
Serial0.2 is up, line protocol is up
  Checksums enabled, MTU 1500, Encapsulation FRAME-RELAY
  ERPDUs enabled, min. interval 10 msec.
  RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
  Congestion Experienced bit set at 4 packets
  CLNS fast switching disabled
  CLNS SSE switching disabled
  DEC compatibility mode OFF for this interface
  Next ESH/ISH in 43 seconds
  Routing Protocol: IS-IS
    Circuit Type: level-1-2
    Interface number 0x2, local circuit ID 0x101
    Level-1 Metric: 10, Priority: 64, Circuit ID: 0000.0000.000B.01
    Number of active level-1 adjacencies: 0
    Level-2 Metric: 10, Priority: 64, Circuit ID: 0000.0000.000B.01
    Number of active level-2 adjacencies: 1
    Next IS-IS Hello in 2 seconds
Serial0.3 is up, line protocol is up
  Checksums enabled, MTU 1500, Encapsulation FRAME-RELAY
  ERPDUs enabled, min. interval 10 msec.
  RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
  Congestion Experienced bit set at 4 packets
  CLNS fast switching disabled
  CLNS SSE switching disabled
  DEC compatibility mode OFF for this interface
  Next ESH/ISH in 11 seconds
  Routing Protocol: IS-IS
    Circuit Type: level-1-2
    Interface number 0x1, local circuit ID 0x100
    Level-1 Metric: 10, Priority: 64, Circuit ID: 0000.0000.000C.01
    Number of active level-1 adjacencies: 0
    Level-2 Metric: 10, Priority: 64, Circuit ID: 0000.0000.000B.00
    Number of active level-2 adjacencies: 1
Next IS-IS Hello in 3 seconds

1.	Identify the DIS on the Ethernet segment. How was this information apparent?
2.	If Router A died, what would the effect be on the network?
3.	Is summarization possible only on the routers entering the WAN cloud, or is it possible on the networks not shown in the figure, but on the other side of the routers? Give reasons for your answers.