| 1: | What command is used to configure the Integrated IS-IS router process? |
| A1: | The router isis global configuration command starts the routing process for integrated IS-IS. |
| 2: | What is the default routing level on a Cisco router? |
| A2: | By default, the routing process for Integrated IS-IS runs as a Level 1-2 router. |
| 3: | What command is used to configure Integrated IS-IS routing on the interface? |
| A3: | The ip router isis interface command is used to start Integrated IS-IS routing on the interface. |
| 4: | How is the NET address configured on the router? |
| A4: | Under the command that started the routing process for Integrated IS-IS, enter the net command followed by the full network address. |
| 5: | What command is used to show the state of adjacencies on the router? |
| A5: | The show clns neighbor and show clns interface commands both display the adjacencies. The show clns neighbor command gives information as to 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: | What command identifies the designated intermediate system router for your LAN? |
| A6: | 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: | Explain briefly what show isis database reveals. |
| A7: | 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: | What command reveals the trigger for the last SPF calculation on the router? |
| A8: | The show isis spf-log command shows the trigger for the last 20 occurrences for which the SPF calculation was run. |
| 9: | For Frame Relay, when would you configure the map command with the broadcast parameter? |
| A9: | 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 the efficient use of IP subnets. |
| 10: | Which command is used to display all update packets that are both received and sent by a router? |
| A10: | 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 sequence number PDUs (CSNPs and PSNPs) and LSPs that are detected by the router. |
| 11: | State two reasons why a router may not be able to find a neighbor. |
| A11: | For an adjacency to be formed and maintained , both interfaces must agree on the following: -
- The same MTU must be configured on both interfaces. -
- If one of the routers is configured as Level 1, both routers must have Level 1 capability. -
- The system IDs must be unique to the router. -
- Level 1 routers must be in the same area. -
- If the routers are in different areas, at least one of the routers must be Level 1-2. -
- The authentication configuration must be the same on both routers. -
- The Hello timers (including the holddown timer) must match. If one router has a Hello timer of 40 seconds, the defaults on the other router would time out the holddown timer and purge the LSP, resulting in a flapping link and endless SPF calculations. |
| 12: | Which command shows the LSPs in detail? |
| A12: | The command show isis database detail shows the LSPs in detail. |
| 13: | How would you ensure that an adjacency has been established? |
| A13: | The commands that display the interface and the adjacency on the local router are either the show clns neighbor or the show clns interface . |
| 14: | What are the steps required for a basic configuration in IS-IS? |
| A14: | 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. |
| 15: | Give the commands required to summarize the networks 10.10.0.0 through to 10.10.255.0 into another area of IS-IS. |
| A15: | The commands required to summarize the networks 10.10.0.0 through to 10.10.255.0 into another area of IS-IS are: -
- router isis -
- summary-address 10.10.0.0 255.255.0.0 |
| 16: | Which command verifies the circuit type and the metric? |
| A16: | The command show clns interface shows both the circuit type, or routing level, of the interface and the IS-IS metric for outgoing packets. |
| 17: | Which network topology defaults in the Broadcast mode? |
| A17: | Essentially, all networks, except true point-to-point topologies, are treated as broadcast networks. That means Ethernet, Token Ring, FDDI, ATM, Frame Relay, and X.25 are all seen as broadcast networks. |
| 18: | For which WAN topology is a point-to-point configuration recommended? |
| A18: | 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. |
| 19: | When is it necessary to map CLNS to the DLCI? |
| A19: | 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 IP routing table. Remember that these are IP routes carried in the IS-IS routing protocol. It is IS-IS that updates the IP routing table. |
| 20: | In the show clns interface command, it is possible to identify the DIS on a multiaccess link. Which field in the output screen of this command would show the DIS for the segment? |
| A20: | 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. |
