Which command prevents Layer 2 loops if the switch stops receiving spanning-tree keepalives on
port ge-1/0/1?
A.
[edit protocols rstp]
user@switch# show
interface ge-1/0/1 {
bpdu-block;
}
B.
[edit protocols layer2-control]
user@switch# show
interface ge-1/0/1 {
bpdu-time-out-action {
block;
alarm;
}
}
C.
[edit protocols layer2-control]
user@switch# show
bpdu-block {
interface ge-1/0/1;
}
D.
[edit protocols rstp]
interface ge-1/0/1
{
no-root-port;
}
Explanation:
D is incorrect
If the bridge receives superior STP bridge protocol data units (BPDUs) on a root-protected interface, that interface transitions to a root-prevented STP state (inconsistency state) and the interface is blocked. This blocking prevents a bridge from being elected the root bridge. When the bridge stops receiving superior STP BPDUs on the root-protected interface, interface traffic is no longer blocked.When root protect is enabled on an interface, it is enabled for all spanning-tree protocol instances on that interface. The interface is blocked only for those instances that receive superior BPDUs.
C and A are incorrect
If a BPDU is received on the interface, the system will disable the interface and
stop forwarding frames out the interface until the bridging process is restarted.
You need to configure loop protection.
When loop protection is enabled, the spanning-tree topology detects root ports and blocked ports and makes sure both keep receiving BPDUs. If a loop-protection-enabled interface stops receiving BPDUs from its designated port, it reacts as it would react to a problem with the physical connection on this interface. It doesn’t transition the interface to a forwarding state, but instead transitions it to a loop-inconsistent state. The interface recovers and then it transitions back to the spanning-tree blocking state as soon as it receives a BPDU.
The only answer with: is B
bpdu-timeout-action {
block;
log;
}
0
0
BTW, part of that new 80Q JN0-647 dumps FYI:
https://drive.google.com/open?id=0B-ob6L_QjGLpejBJUUI1X2NuU3M
Best Regards!
0
0