Top 15 CCNA Interview Questions with Answers
1) What is routing on a network?
This might seem like a basic question, but the interviewer might ask it just to see if you know the basics. Routing is done by routers. Routers have a routing table that send network traffic from one location to another location or segment on the network. Routers reduce network traffic compared to regular hubs. When a user sends network traffic across the network, a hub broadcasts to all segments of the network. With a router, the device analyzes the TCP/IP packet, sees the destination location, and then uses its lookup table to route the packet to the right network segment and destination. Switches also route traffic in a similar fashion.
2) What does MTU stand for?
MTU stands for “Maximum Transmission Unit.” When you configure a router, a default MTU is set. MTU determines the maximum size of a packet that is sent across the network. You can increase MTUs across the network, but this setting generally slows down the network compared to smaller MTU settings. Some network applications require larger MTU sizes, and that’s when you need to manually configure MTU sizes on your routers.
3) What is subnetting on your network?
Subnetting is a way to segment your network into smaller “groups.” Subnetting is accomplished by manipulating the subnet mask, which is distributed to desktop computers and routers. Subnetting allows you to create smaller networks within your network, which then reduces congestion on larger networks.
4) Define bandwidth in terms of network architecture
While the term bandwidth is thrown around for most basic networking speeds and capacity, bandwidth is technically the data capacity of a network. It measures the volume of data for a transmission connection. Bandwidth is measured in kilobits per second or “Kbps.”
5) What is the difference between user mode and privileged mode on a Cisco router?
These two modes are somewhat self-explanatory. The user mode allows the user to view router status and basic system information. With privileged mode access status, the router can be configured and all status messages and errors can be viewed. User mode and privileged mode separates standard users on the network and network administrators who need to not only view router status but also make changes to the router’s configurations.
6) What are three types of LAN traffic?
Unicasts – intended for one host.
Broadcasts – intended for everyone.
Multicasts – intended for a only a subset or group within an entire network.
7) What is the Spanning-Tree Protocol (STP)?
Ans. STP is a loop-prevention bridge-to-bridge protocol. Its main purpose is to dynamically maintain a loop-free network. It does this by sending out Bridge Protocol Data Units (BPDUs), discovering any loops in the topology, and blocking one or more redundant links.
8) What is the difference between a routing protocol and a routed protocol?
Ans. Routing protocols determine how to route traffic to the best location of a routed protocol. Examples of routing protocols are RIP, EIGRP, OSFP, and BGP. Examples of routed protocols are IP and IPX.
9) What is subnetting?
Subnetting is the process of creating smaller networks from a big parent network. Being a part of a network, each subnet is assigned some additional parameters or identifier to indicate its subnet number.
10) What is a VLAN? What does VLAN provide?
Vlan is a logical grouping or segmenting a network connected to administratively defined ports on a switch, they provide Broadcast control, Security and Flexibility.
11) What is the MAC address?
The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.
12) How does STP maintain a loop-free network?
STP maintains a loop-free network by
Electing a root bridge
Electing a root port on each non root bridge
Electing designated ports
Putting in the blocking state any port that is not a root port or designated port
13) What is Frame Relay?
An industry standard, Frame Relay is a switched data link layer protocol that uses virtual circuits to identify the traffic that belongs to certain routers. It provides dynamic bandwidth allocation and congestion control.
14) Administrative distance of various routing protocols:
• Connected – 0
• Static – 1
• eBGP/ BGP – 20
• EIGRP – 90
• OSPF – 110
• IS-IS- 115
• RIP – 120
• iBGP – 200
• Unknown – 255
15) Port numbers:
• Telnet – 23
• DNS – 53
• SSH – 22
• FTP – 21 (FTP data- 20, FTP control – 21)
• SMTP – 25
• Whois – 43
• SFTP – 115
• SNMP – 161
• BGP – 179
• LDAP – 389
• DHCP client- 546
• DHCP Server – 547
• POP3 – 110
Source : Corvit training
