Computer Networks

Duplex mismatch occurs when one end is autonegotiating (switch) and defaults to half-duplex while the other end (PC) is hardcoded to full-duplex. This causes late collisions and packet loss on the full-duplex side, leading to slow and intermittent connectivity. The solution is to ensure both ends autonegotiate or both are manually configured to the same duplex setting.

The routing table entry shows O (OSPF) [110/129]. The first number (110) is OSPF's administrative distance. The second number (129) is the route metric/cost, calculated from bandwidth and delay (option A). Option B incorrectly interprets this as clock rate. Option C incorrectly states this is hop count (OSPF uses cost, not hops). Option D incorrectly says this is update count. The 129 is the composite metric for this OSPF route.

A /24 subnet mask (255.255.255.0) provides 256 total IP addresses, with 254 usable for hosts after subtracting the network address and broadcast address. The network address 192.168.32.0 with this mask gives the range 192.168.32.1 to 192.168.32.254 for host assignment. Option A (/16) would provide 65,534 hosts, which is excessive. Option C (/23) would give 510 hosts, and Option D (/21) would provide 2,046 hosts - both far more than needed.

PPP Multilink (MP) protocol allows load balancing across multiple interfaces by bundling them into a single logical link. This distributes traffic and provides increased bandwidth through aggregation. Option A (Callback) is for dial-backup functionality. Option C (Compression) reduces data size but doesn't load balance. Option D (Error detection) ensures data integrity but doesn't distribute traffic across interfaces.

The show interface command output primarily reveals issues at the Data Link layer (Layer 2) of the OSI model, as it displays information about interface status, CRC errors, framing errors, and collisions - all Layer 2 phenomena. Physical layer issues would show as line down or excessive carrier transitions. Network layer problems would be visible in routing tables and IP-specific commands. Transport and Application layer issues require different diagnostic commands.

When HostA communicates with the web server, it must use the web server's actual public IP address (172.30.20.2) as the destination. R1 performs NAT on the 10.1.1.0/24 network, translating HostA's private source address to a public address. R2 performs NAT for the 192.168.1.0/24 network on the server side. The destination IP in HostA's IP header remains the web server's public address throughout; only the source address gets translated by NAT.

PAT (Port Address Translation) uses unique source port numbers to distinguish between multiple private IP addresses mapping to a single registered public IP address. This allows many hosts to share one global address simultaneously. Option A incorrectly describes syntax - 'overload' is used in the NAT command, not access-list statements. Option B is wrong because static NAT maps one-to-one, not one-to-many. Option C is incorrect because dynamic NAT does not guarantee the same global address across multiple connections.

When serial interfaces can ping each other but FastEthernet interfaces cannot, the issue is typically incorrect default route configuration. One router's default route likely points to the wrong next-hop address or interface, causing packets destined for the FastEthernet network to be sent incorrectly. If FastEthernet interfaces were disabled, the serial ping would also likely fail. A routing protocol is not necessary if static routes are configured. Default gateway configuration applies to hosts, not routers.

OSPF neighbors must have matching hello and dead timer intervals to form adjacencies. These timers determine how often OSPF sends hello packets and when a neighbor is declared down. Mismatched timers prevent neighbor discovery even if other parameters match. OSPF process IDs are local to each router and don't need to match. Autonomous system IDs are used in BGP, not OSPF. Identical network types would actually help OSPF work, not prevent it.

After a collision in CSMA/CD, hosts wait for their backoff period to expire. Once the backoff time elapses, they must return to listen-before-transmit mode to check if the channel is idle before attempting retransmission. This prevents immediate re-collision. Hosts do not have priority - they compete fairly for channel access.

With a /27 mask (255.255.255.224), the subnet size is 32 addresses. The subnet starting at 172.16.134.64 would have network address 172.16.134.64, usable host range 172.16.134.65-94, and broadcast address 172.16.134.95. Therefore 172.16.134.64 is the network address, not a usable host address.