Direct Connectivity and Configurations of R1 and R2
Question
-- 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 {
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;
}
}
}
lo0 {
unit 0 {
family inet {
address 10.100.10.2/32;
}
family iso {
address 49.1001.0010.0200.00;
}
}
}
}
protocols {
isis {
interface ge-1/1/0.0;
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 happens as a result of the configurations?
Answers
Explanations
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A. B. C. D.C
Referring to the exhibit, R1 and R2 are connected to each other via the interface ge-1/1/0, and they are configured to run the ISIS routing protocol.
R1 is configured with the address 10.100.1.1/30 on its interface ge-1/1/0. This means that the IP address of R1's interface is 10.100.1.1, and the subnet mask is 255.255.255.252.
Similarly, R2 is configured with the address 10.100.1.2/30 on its interface ge-1/1/0. This means that the IP address of R2's interface is 10.100.1.2, and the subnet mask is 255.255.255.252.
The ISIS routing protocol is configured on both R1 and R2, and they are both configured to advertise their loopback interfaces. R1's loopback interface has the IP address 10.100.10.1/32, and its ISO address is 49.1001.0010.0100.00. R2's loopback interface has the IP address 10.100.10.2/32, and its ISO address is 49.1001.0010.0200.00.
In the ISIS configuration on R1, the interface ge-1/1/0.0 is configured with the "level 2 disable" command, which means that the interface will not participate in Level 2 routing. However, the loopback interface lo0.0 is configured to participate in ISIS.
In the ISIS configuration on R2, both interfaces ge-1/1/0.0 and lo0.0 are configured to participate in ISIS.
Given this configuration, the answer to the question "what happens as a result of the configurations?" is that a Level 1 adjacency will form between R1 and R2, but no Level 2 adjacency will form. This is because R1 has disabled Level 2 routing on the ge-1/1/0 interface, but it is still advertising its loopback interface as a Level 1 route. R2 is configured to participate in both Level 1 and Level 2 routing on both of its interfaces. Therefore, R2 will form a Level 1 adjacency with R1's loopback interface, but it will not form a Level 2 adjacency with R1, because R1's ge-1/1/0 interface is not participating in Level 2 routing.
