Exam N10-008 topic 1 question 588 discussion

C. ICMP If the network technician is unable to ping the server but can establish connectivity using Telnet, it suggests that ICMP (Internet Control Message Protocol) traffic is being blocked by the firewall. Ping uses ICMP to test connectivity by sending Echo Request messages and expecting Echo Reply messages in response. If ICMP is blocked, ping will fail while other protocols like TCP (Telnet uses TCP) may still work. So, the correct answer is C. ICMP.

ICMP (Internet Control Message Protocol): ICMP includes the ping command, which tests reachability and round-trip time to a host. If the technician can’t ping the server but can use telnet (which uses TCP), ICMP might be blocked. LIKELY the protocol is being blocked. TCP (Transmission Control Protocol): TCP is used for reliable, connection-oriented communication. Telnet uses TCP, and the technician can verify connectivity using it. Not the cause of the issue. Therefore, the most probable answer is Option C (ICMP). The firewall may be configured to block ICMP requests, preventing successful pings to the web server.

found this one Cisco website "Telnet runs over the TCP protocol and denying icmp echo will not directly stop telnet."