JNCIS-SP: Juniper Networks Certified Specialist – Service Provider Routing — Question 7
-- Exhibit --
user@R1> show
interfaces {
ge-1/1/0 {
unit 0 {
family inet {
address 10.100.1.1/30;
}
family iso;
}
}
lo0 {
unit 0 {
family inet {
address 10.100.10.1/32;
}
family iso {
address 49.1001.0010.0100.00;
}
}
}
}
protocols {
isis {
level 1 disable;
interface ge-1/1/0.0 {
level 2 disable;
}
interface lo0.0;
}
}
user@R2> show
interfaces {
ge-1/1/0 {
unit 0 {
family inet {
address 10.100.1.2/30;
}
family iso {
mtu 1496;
}
}
}
lo0 {
unit 0 {
family inet {
address 10.100.10.2/32;
}
family iso {
address 49.1002.0010.0200.00;
}
}
}
}
protocols {
isis {
interface ge-1/1/0.0 {
level 2 disable;
}
interface lo0.0;
}
}
-- Exhibit --
Click the Exhibit button.
Referring to the exhibit, R1 and R2 are directly connected using interface ge-1/1/0.
What is the reason the IS-IS adjacency fails?
Answer options
- A. R2 has an MTU value of 1496 configured on ge-1/1/0.
- B. R2 and R1 have different area IDs.
- C. R1 is configured for Level 2, and R2 is configured for Level 1.
- D. R1 is configured for both Level 1 and Level 2 to be disabled.
Correct answer: B
Explanation
The correct answer is B because IS-IS requires that routers participate in the same area for adjacency to form. Since R1 and R2 have different area IDs, the adjacency will not be established. Option A is incorrect as MTU mismatches would cause issues but not specifically the adjacency failure. Options C and D are also incorrect because both routers are configured to disable levels, which does not directly prevent adjacency due to area ID differences.