Chapter 10

"Do I Know This Already?"

9.B, C, D
11.B, C, D
12.C and D


1.The router isis global configuration command starts the routing process for integrated IS-IS.
2.By default, the routing process for Integrated IS-IS runs as a Level 1-2 router.
3.The ip router isis interface command is used to start Integrated IS-IS routing on the interface.
4.Under the command that started the routing process for Integrated IS-IS, enter the net command followed by the full Network Entity Title.
5.The show clns neighbor and show clns interface commands both display the adjacencies. The show clns neighbor command shows information on the state of the link, the type of routing performed on the link, the data-link address (SNPA) of the link, and the holdtime, or how long since it received the last Hello.
6.The designated intermediate system (DIS) is identified in the output screen of the show clns interface command or any show command that shows the pseudonode, such as show isis database or show clns neighbors. If the medium is multiaccess broadcast, the Circuit ID field shows the ID of the pseudonode. The pseudonode is identified by the nonzero value in the octet following the system ID of the DIS (for example, R2.01).
7.The show isis database command displays the LSPs in the link-state database. This database should be identical on every router in the area.
8.The show isis spf-log command shows the trigger for the last 20 occurrences for which the SPF calculation was run.
9.The frame-relay map command with the broadcast parameter is used in a fully meshed environment and when the network is multiaccess. This allows the election of a DIS, streamlining of adjacencies, and efficient use of IP subnets.
10.The command that shows all the Integrated IS-IS packets both sent and received by the router is debug isis update-packets. These packets are the CSNPs, PSNPs, and LSPs that are detected by the router.
11.The command show isis database detail shows the LSPs in detail.
12.The commands that display the interface and the adjacency on the local router are show clns neighbor or show clns interface.
13.The steps required for a basic configuration in IS-IS are
  • Define the areas and addresses.

  • Enable IS-IS on the router.

  • Configure the NET address.

  • Enable IS-IS on the appropriate interfaces.

14.The commands required to summarize the networks through to into another area of IS-IS are
  • router isis

  • summary-address

15.The command show clns interface shows both the circuit type, or routing level, of the interface and the IS-IS metric for outgoing packets.
16.In an NBMA multipoint configuration, subinterfaces and a point-to-point IS-IS network should be configured. NBMA multipoint topologies should be avoided, because, although they can be made to work, they require complex configuration and do not work with the strengths of the IS-IS routing protocol.
17.It is necessary to map CLNS to the DLCI in a NBMA Frame Relay network that is using a point-to-multipoint topology.

The frame-relay map ip command maps the IP destination address to the outgoing DLCI and defines the interface as a broadcast interface. Integrated IS-IS uses the links as if they were truly a broadcast link and elects a DIS.

The frame-relay map clns command maps to the CLNS process on the destination router.

Without the second command, no routes appear in the IP routing table because CLNS does not receive the frames to populate the LSDB. Remember that these are IP routes carried in the IS-IS routing protocol. It is IS-IS that updates the IP routing table.

18.The field that shows the DIS is the circuit ID. This field shows the pseudonode ID, which is the system ID of the DIS. It is easily identifiable, as it has a value greater than 0x00 in the octet after the system ID.