JNCIS-ENT IS IS Practice Test 2 — 15 Questions

Question 1

You want to influence the path selection for IS-IS traffic. You decide to change the metric. Which TLV is used to carry wide metrics?

Accepted Answer

TLV 22. TLV 22 (Extended IS Reachability) is used to carry wide metrics in IS-IS.

Answer

TLV 135

Answer

TLV 2

Answer

TLV 128

Question 2

In a multi-access network, which PDU is responsible for the DIS election?

Accepted Answer

IIH PDU. The IIH (IS-IS Hello) PDU contains the priority field used for DIS election on broadcast segments.

Answer

CSNP

Answer

LSP

Answer

PSNP

Question 3

What is the default IS-IS metric for an interface in Junos?

Accepted Answer

10. The default IS-IS metric in Junos is 10.

Answer

1

Answer

0

Answer

100

Question 4

What is the effect of changing the reference bandwidth in IS-IS?

Accepted Answer

It has no effect on IS-IS.. IS-IS does not have a reference bandwidth concept like OSPF; metrics are configured manually or via interface cost.

Answer

It automatically recalculates all interface metrics.

Answer

It increases the hello interval.

Answer

It forces all links to use narrow metrics.

Question 5

When using authentication in IS-IS, where can you apply the password?

Accepted Answer

At both the interface and global levels.. IS-IS authentication can be applied to the interface level or the global level (area/domain).

Answer

Only on the loopback interface.

Answer

Only at the global level.

Answer

Only at the interface level.

Question 6

What happens if you have an LSP with an expired lifetime?

Accepted Answer

The LSP is removed from the LSDB.. When an LSP's remaining lifetime reaches zero, it is purged from the database after a short period.

Answer

The router immediately crashes.

Answer

The LSP is flooded to all neighbors.

Answer

The router re-elects a new DIS.

Question 7

Why would you set an interface to 'passive' in IS-IS?

Accepted Answer

To include the network in the LSP without forming an adjacency.. Setting an interface to passive allows the router to advertise the network as reachable without attempting to form an adjacency on that interface.

Answer

To speed up the DIS election process.

Answer

To force the interface to be a point-to-point link.

Answer

To enable authentication on that interface.

Question 8

You are observing that your IS-IS routers are not synchronizing their databases. You check the CSNP settings. What is the role of the CSNP on a broadcast segment?

Accepted Answer

To provide a summary of the entire database to neighbors.. CSNPs (Complete Sequence Number PDUs) are sent by the DIS to ensure all routers have the same Link State Database.

Answer

To acknowledge individual LSPs.

Answer

To initiate the DIS election.

Answer

To request specific missing LSPs.

Question 9

Which of the following is required for two routers to form a Level 2 adjacency?

Accepted Answer

Matching Level 2 support.. For Level 2 adjacencies, the interfaces must be in the same level (or both be L1/L2) and share the same network segment.

Answer

Identical hostname configurations.

Answer

Matching Area Addresses.

Answer

Identical System IDs.

Question 10

Which of the following is a valid IS-IS PDU type?

Accepted Answer

Link State PDU. IIH, LSP, CSNP, and PSNP are the four standard IS-IS PDU types.

Answer

Routing Update PDU

Answer

Database Description PDU

Answer

Hello PDU

Question 11

How does a router determine its System ID?

Accepted Answer

It is manually configured.. The System ID is manually configured in the 'set protocols isis system-id' hierarchy.

Answer

It is learned via ARP.

Answer

It is automatically derived from the MAC address.

Answer

It is assigned by the DIS.

Question 12

What is the purpose of the 'lsp-lifetime' command?

Accepted Answer

To set the duration for which an LSP is valid.. The 'lsp-lifetime' command sets the duration after which an LSP is considered invalid if not refreshed.

Answer

To define how often the DIS sends Hellos.

Answer

To limit the number of LSPs in the database.

Answer

To set how long the adjacency stays up.

Question 13

Which level is enabled by default in Junos when configuring IS-IS on an interface?

Accepted Answer

Level 1 and Level 2. By default, interfaces in Junos IS-IS are enabled for both Level 1 and Level 2.

Answer

None

Answer

Level 2 only

Answer

Level 1 only

Question 14

How do you configure an interface to be point-to-point when using IS-IS?

Accepted Answer

set protocols isis interface point-to-point. You use the 'set protocols isis interface point-to-point' command to force point-to-point mode.

Answer

set protocols isis interface-type point-to-point

Answer

set interfaces <name> unit 0 family iso point-to-point

Answer

set protocols isis link-type p2p

Question 15

You are configuring multi-topology IS-IS. What does this allow?

Accepted Answer

Running separate topologies for different address families.. Multi-topology IS-IS allows for separate routing topologies for different protocol families (e.g., IPv4 and IPv6).

Answer

Load balancing over different physical paths.

Answer

Creating multiple areas within a single instance.

Answer

Increasing the maximum MTU.