Computer Knowledge

Computer Networks

2,614 Questions

Computer networks involve the architecture, protocols, and security measures used for digital communication. This collection covers OSI model layers, IP addressing, data transmission, and cryptographic standards. These concepts are vital for the computer knowledge sections of banking and government exams.

OSI model layersNetwork protocolsIP subnet maskingData encryption standardsServer configurationsNetwork commands

Computer Networks Questions

Multiple choice

Which of the following statements is true about wildcard masks?

  1. Inverting the subnet mask will always create the wildcard mask.

  2. A wildcard mask identifies a network or subnet bit by using a 1.

  3. The same function is performed by both a wildcard mask and a subnet mask.

  4. When a 0 is encountered in a wildcard mask, the IP address bit must be checked.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In wildcard masks, a 0 bit means the corresponding IP address bit must match exactly, while a 1 bit means 'don't care' - the bit can be any value. This is the opposite of subnet masks, where 1 means network portion and 0 means host portion. Wildcard masks are commonly used in access control lists and OSPF configuration.

Multiple choice

Refer to the exhibit. Router1 and Router2 are running the RIPv1 protocol. The network administrator configures the command network 10.1.0.0 on Router1. What network will Router1 advertise to Router2?

  1. 10.1.0.0/16

  2. 10.1.0.0/8

  3. 10.0.0.0/16

  4. 10.0.0.0/8
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

RIPv1 is a classful routing protocol that does not include subnet mask information in its updates. When network 10.1.0.0 is configured, RIPv1 advertises the entire classful network 10.0.0.0/8 because it assumes all subnets within that classful network belong to the same major network. This is a limitation of classful protocols.

Multiple choice

Which layer of the OSI model supplies services that allow user to interface with the network?

  1. physical

  2. session

  3. network

  4. application

  5. presentation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The Application layer (layer 7) of the OSI model provides network services directly to user applications and software. This layer includes protocols like HTTP, FTP, SMTP, and DNS that allow users to interact with the network through applications such as web browsers and email clients.

Multiple choice

Two routers Rtr1 and Rtr2 are both configured with RIP only. What will be the result when Rtr1 receives a routing update that contains a higher cost path to a network already in its routing table?

  1. The update information will replace the existing routing table entry.

  2. The update information will be added to the existing routing table.

  3. The existing routing table entry will be deleted from the routing table and all routers will exchange routing updates to reach convergence.

  4. The update will be ignored and no further action will be taken.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When a RIP router receives a route to a destination that it already has in its routing table, it compares the metrics. RIP only keeps the route with the lowest cost (fewest hops). If the received update has a higher cost than the existing entry, the update is ignored and the existing better route is retained.

Multiple choice

A route to a destination network is learned from multiple routing protocols. What is used by a Cisco router to select the preferred route to the destination that will be installed in the routing table?

  1. metric

  2. route prefix

  3. update timer

  4. administrative distance
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Administrative distance is the criterion used by Cisco routers to select between routes learned from different routing protocols or sources. Each routing source has a default AD value (e.g., connected=0, static=1, EIGRP=90, OSPF=110, RIP=120). The route with the lowest AD is installed in the routing table, regardless of the routing protocol's metric.

Multiple choice

What action does a link-state take immediately upon receipt of an LSP from a neighboring router?

  1. floods the LSP to neighbors

  2. calculates the SPF algorithm

  3. runs the Bellman-Ford algorithm

  4. computes the best path to the destination network
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a link-state router receives a Link State Packet (LSP) from a neighbor, it immediately floods this LSP to all its other neighbors (except the one it received it from). This flooding ensures all routers quickly receive the same topology information. SPF calculation happens later, after the LSP is processed and added to the LSDB.

Multiple choice

What is important to consider while configuring the subinterfaces of a router when implementing inter-VLAN routing?

  1. The physical interface must have an IP address configured.

  2. The subinterface numbers must match the VLAN ID number.

  3. The no shutdown command must be given on each subinterface.

  4. The IP address of each subinterface must be the default gateway address for each VLAN subnet.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For inter-VLAN routing, each subinterface must have the default gateway IP address for devices in that VLAN to use for routing. The physical interface itself typically does not need an IP address configured. While it's common practice to match subinterface numbers to VLAN IDs, this is not a technical requirement, and the no shutdown command is generally issued on the physical interface, not each subinterface.

Multiple choice

Which IP address and wildcard mask would be used in an ACL to block traffic from all hosts on the same subnet as host 192.168.16.43/28?

  1. access-list 10 deny 192.168.16.0 0.0.0.31

  2. access-list 10 deny 192.168.16.16 0.0.0.31

  3. access-list 10 deny 192.168.16.32 0.0.0.16

  4. access-list 10 deny 192.168.16.32 0.0.0.15
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The host 192.168.16.43/28 belongs to the subnet 192.168.16.32/28 (addresses 192.168.16.32 to 192.168.16.47). A /28 mask corresponds to a wildcard mask of 0.0.0.15. The ACL statement must use the network address (192.168.16.32) paired with the wildcard mask (0.0.0.15) to match all hosts in that subnet.

Multiple choice

When PVST+ was developed, the Bridge ID was modified to include which information?

  1. bridge priority

  2. MAC address

  3. protocol

  4. VLAN ID
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

PVST+ (Per-VLAN Spanning Tree Plus) runs a separate spanning tree instance for each VLAN. To make this work, the Bridge ID was modified to include the VLAN ID, allowing each VLAN to have a different root bridge if desired. This modification maintains backward compatibility while enabling per-VLAN spanning tree calculations. The Bridge ID still contains priority and MAC address, but the VLAN ID extension is what makes PVST+ possible.

Multiple choice

What range of networks will be advertised in the OSPF updates by the command Router1(config-router)# network 192.168.0.0 0.0.15.255 area 100?

  1. 192.168.0.0/24 through 192.168.0.15/24

  2. 192.168.0.0/24 through 192.168.15.0/24

  3. 192.168.16.0/24 through 192.168.255.0/24

  4. 192.168.15.0/24 through 192.168.31.0/24

  5. 192.168.15.0/24 through 192.168.255.0/24
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The wildcard mask 0.0.15.255 matches networks where the third octet ranges from 0 to 15. This means 192.168.0.0/24 through 192.168.15.0/24 will be advertised. The wildcard mask works by having 0 bits that must match exactly and 1 bits that can vary. The binary of 15 is 00001111, allowing the first 4 bits to match (giving 0-15) while the first two octets and last octet are fixed.