Which of the following protocols work at the Network layer of the OSI model? (ISC)2 CISSP-ISSAP Exam

Question

Options

• ARouting Information Protocol (RIP)
• BFile Transfer Protocol (FTP)
• CSimple Network Management Protocol (SNMP)
• DInternet Group Management Protocol (IGMP)

• A
  96% (24)
• B
  4% (1)

Explanation

RIP and IGMP both operate at Layer 3 (Network) of the OSI model. RIP is a distance-vector routing protocol that exchanges routing table information between routers using IP-level communication, making it a Network-layer protocol. IGMP manages IPv4 multicast group memberships between hosts and routers - it's encapsulated directly in IP packets, firmly placing it at Layer 3 alongside protocols like ICMP.

FTP (B) operates at Layer 7 (Application), used for transferring files between hosts. SNMP (C) also sits at Layer 7 (Application), used for monitoring and managing network devices - despite its name suggesting network involvement, it's an application that monitors the network, not one that routes within it.

Memory tip: Ask yourself, "Does this protocol move or address packets, or does it serve users/applications?" Layer 3 protocols (IP, ICMP, IGMP, RIP, OSPF) handle packet delivery and routing logic. If you can open it in a browser or use it to transfer files/data as an end-user (FTP, SNMP, HTTP), it's almost certainly Application layer (Layer 7).

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