After a network outage, a PC technician is unable to ping various network devices. The network
administrator verifies that those devices are working properly and can be accessed securely.
Which of the following is the MOST likely reason the PC technician is unable to ping those
devices?
A.
ICMP is being blocked
B.
SSH is not enabled
C.
DNS settings are wrong
D.
SNMP is not configured properly
Explanation:
Key concept: Unable to “ping”
Now for a definition: ICMP is a protocol that is commonly used by tools such as ping, traceroute, and “pathing”. ICMP offers no information If ICMP request queries go unanswered, or ICMP replies are lost or blocked.
It is used by network devices, including routers, to send error messages and operational information indicating, for example, that a requested service is not available or that a host or router could not be reached
A very interesting question:
If ICMP is being blocked, how did he PC technician manage to ping the network devices prior to the outage?
Unless he never actually could ping any devices by virtue of being a PC technician and that was left to the Network Administrators.
But, once ICMP is blocked, it is blocked to all – PC technicians and Network Administrators alike.
More and more it is proven that blocking ICMP is not a very good idea after all
Blocking it makes remote administration a nightmare for example, as we can never tell whether a device is up or down, and we will no longer get important error messages and relevant operational information.
In short, ICMP is blocked, and it was so even before the outage ever took place.
For a process of elimination, the other answers simply do not fit the bill.
B- SSH does not need to be enabled for me to be able to ping.
C- Even if DNS settings were wrong, I would get a (perhaps wrong) ping reply
D- SNMP is a monitoring tool which will not affect ping results. It is possible to monitor SNMP nodes without ICMP connectivity, but that takes some doing and manual configuration.
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