MODULE 8

What are the four basic operations of the network layer?

A: Addressing end devices, encapsulation, routing, and de-encapsulation.

What are the three key characteristics of IP?

A: Connectionless, best effort, and media independent.

Why is IP considered "connectionless"?

A: It does not establish a connection before sending packets and does not use acknowledgments or pre-notifications.

What does "best effort" mean in IP?

A: IP does not guarantee packet delivery, retransmission, or error recovery.

How is IP media independent?

A: It operates over any physical medium (copper, fiber, wireless) without modification.

What is the purpose of the TTL field in IPv4?

Time-to-Live (TTL) is a hop count; the packet is discarded if TTL reaches 0.

What are the two most important fields in an IPv4 header?

A: Source IP address and destination IP address.

How does IPv6 improve upon IPv4?

• Larger address space (128-bit vs. 32-bit).

• Simplified header (fixed 40 bytes, no fragmentation fields).

• Eliminates need for NAT.

What replaces the TTL field in IPv6?

Hop Limit.

How does a host determine if a destination is local or remote?

• IPv4: Uses its own subnet mask and destination IP.

• IPv6: Uses the network prefix from the local router.

What is the role of a default gateway (DGW)?

A router/L3 switch that forwards traffic from a LAN to remote networks.

What happens if a host has no default gateway configured?

It cannot communicate with devices outside its local network.

What command shows the routing table on a Windows host?

route print or netstat -r.

What are the three types of routes in a router’s routing table?

1. Directly connected networks.

2. Remote networks (static/dynamic).

3. Default route (0.0.0.0/0).

How does a router forward a packet?

1. De-encapsulates the Layer 2 frame.

2. Matches the destination IP to the routing table (longest prefix match).

3. Re-encapsulates and forwards to the next hop.

What is the advantage of dynamic routing over static routing?

Automatically adapts to topology changes (e.g., OSPF, EIGRP).

What does the show ip route command display?

• Route sources (C = connected, S = static, O = OSPF).

• Network paths (directly connected, remote, default).

Why does IPv6 not need fragmentation?

A: It relies on Path MTU Discovery to avoid packet splitting.

What is the purpose of extension headers in IPv6?

A: Provide optional features (e.g., security, mobility support) between the IPv6 header and payload.

What is the key difference between IPv4 and IPv6 headers?

• IPv4: Variable length (20+ bytes), includes checksum/fragmentation fields.

• IPv6: Fixed 40 bytes, no checksum, uses extension headers.