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201 · Question #335

A site has assigned the ICMP monitor to all nodes and a custom monitor, based on the HTTP template, to a pool of web servers. The HTTP based monitor is working in all cases. The ICMP monitor is…

The correct answer is D. The pool members whose nodes are failing the ICMPbased monitor will be marked unavailable. If a node's ICMP monitor fails, all pool members on that node become unavailable, regardless of their individual application-level monitor status, as the underlying server is unreachable.

Section 2: Configure Load Balancing Features

Question

A site has assigned the ICMP monitor to all nodes and a custom monitor, based on the HTTP template, to a pool of web servers. The HTTP based monitor is working in all cases. The ICMP monitor is failing for 2 of the pool member 5 nodes. All other settings are default. What is the status of the monitor is working in all cases?

Options

  • AAll pool members are up since the HTTPbased monitor is successful.
  • BAll pool members are down since the ICMPbased monitor is failing in some cases.
  • CThe pool members whose nodes are failing the ICMPbased monitor will be marked disabled.
  • DThe pool members whose nodes are failing the ICMPbased monitor will be marked unavailable.

How the community answered

(44 responses)
  • A
    18% (8)
  • B
    5% (2)
  • C
    7% (3)
  • D
    70% (31)

Why each option

If a node's ICMP monitor fails, all pool members on that node become unavailable, regardless of their individual application-level monitor status, as the underlying server is unreachable.

AAll pool members are up since the HTTPbased monitor is successful.

The success of the HTTP monitor does not override the failure of the node-level ICMP monitor, as the server itself is considered unreachable.

BAll pool members are down since the ICMPbased monitor is failing in some cases.

Only the pool members residing on the nodes that are failing the ICMP monitor will be affected; other pool members on healthy nodes remain up.

CThe pool members whose nodes are failing the ICMPbased monitor will be marked disabled.

'Disabled' is typically a manual administrative status; an automatic monitor failure usually results in an 'unavailable' or 'down' status.

DThe pool members whose nodes are failing the ICMPbased monitor will be marked unavailable.Correct

When a node's monitor fails, it indicates an issue with the underlying server itself, making any services on that node inaccessible. Consequently, all pool members associated with that node will be marked 'unavailable' by the load balancer, preventing client traffic from being sent to them, even if their application-specific (HTTP) monitor is technically successful.

Concept tested: Interaction of node and pool member health

Source: https://techdocs.f5.com/en-us/bigip-15-0-0/big-ip-local-traffic-management-concepts/monitors.html

Topics

#health monitors#ICMP monitor#HTTP monitor#pool member status

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