Question 1

Which two statements are correct about IS-IS interfaces? (Choose two.)

A. If a point-to-point interface is in both L1 and L2, separate hello messages are sent for each level.
B. If a point-to-point interface is in both 11 and L2, one combined hello message is sent for both levels.
C. If a broadcast interface is in both L1 and L2, separate hello messages are sent for each level.
D. If a broadcast interface is in both L1 and L2, one combined hello message is sent for both levels.

Correct Answer: B, C Explanation:

Intermediate System to Intermediate System (IS-IS) is a link-state routing protocol that supports Level 1 (L1), Level 2 (L2), or both (L1/L2) operations. The way IS-IS sends Hello (IIH) packets depends on whether the interface is point-to-point (P2P) or broadcast (LAN).

Evaluating the Answer Choices

Option A: 'If a point-to-point interface is in both L1 and L2, separate hello messages are sent for each level.'

Incorrect!

On point-to-point (P2P) interfaces, only one combined Hello message is sent for both L1 and L2.

IS-IS P2P Hellos include both Level 1 and Level 2 TLVs in the same message.

This statement is incorrect.

Option B: 'If a point-to-point interface is in both L1 and L2, one combined hello message is sent for both levels.'

Correct!

On point-to-point (P2P) links, IS-IS sends a single Hello message that includes TLVs for both L1 and L2.

This reduces overhead and simplifies adjacency formation.

This statement is correct.

Option C: 'If a broadcast interface is in both L1 and L2, separate hello messages are sent for each level.'

Correct!

On broadcast (LAN) interfaces, IS-IS sends separate Hello messages for L1 and L2.

This is because L1 and L2 use separate Designated IS (DIS) elections and different multicast addresses:

L1 Hellos: Sent to AllL1IS (01:80:C2:00:00:14)

L2 Hellos: Sent to AllL2IS (01:80:C2:00:00:15)

This statement is correct.

Option D: 'If a broadcast interface is in both L1 and L2, one combined hello message is sent for both levels.'

Incorrect!

As stated above, IS-IS sends separate Hello messages for L1 and L2 on broadcast interfaces because they have independent DIS elections.

This statement is incorrect.

Final Answer:

B. If a point-to-point interface is in both L1 and L2, one combined hello message is sent for both levels. C. If a broadcast interface is in both L1 and L2, separate hello messages are sent for each level.

Verification from Juniper Documentation

Juniper IS-IS Configuration Guide confirms:

Point-to-Point (P2P) interfaces send one combined Hello for both levels.

Broadcast interfaces send separate L1 and L2 Hellos due to separate DIS elections.

RFC 1195 (IS-IS Extensions for IPv4) specifies that broadcast networks require distinct Hellos per level.

Question 2

Exhibit

You are asked to exchange routes between R1 and R4 as shown in the exhibit. These two routers use the same AS number Which two steps will accomplish this task? (Choose two.)

A. Configure the BGP group with the advertise-peer-as parameter on R1 and R4.
B. Configure the BGP group with the as-override parameter on R2 and R3
C. Configure the BGP group with the advertise-peer-as parameter on R2 and R3.
D. Configure the BGP group with the as-override parameter on R1 and R4

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