Computer Networking (CCNA level)

The big picture of networking: what a network is made of, the devices that build it, the OSI and TCP/IP models that describe it, and how TCP and UDP carry data between programs using port numbers. After this module you can name every common network device and what it does, place any protocol on its layer, explain encapsulation step by step, and recognise the well-known ports used in the CCNA exam.

1. What a network isA network is two or more devices (nodes) joined by links so they can share data. Small networks in one building are LANs, networks that join cities are WANs, and the internet is a huge network of networks. Speed is measured in bits per second, so remember that one byte is eight bits when you work out download times.25 min
2. Network devicesEach network device has one main job. A NIC connects a computer, a switch joins devices inside a LAN, a router joins different networks, an access point adds Wi-Fi, and a firewall decides which traffic is allowed. Switches split collision domains and routers split broadcast domains. The box your ISP gives you at home is several of these devices in one.30 min
3. The OSI modelThe OSI model splits the job of networking into 7 layers, from the physical signal (Layer 1) up to the application you use (Layer 7). Each layer has its own job and its own name for the data unit: bits, frames, packets, segments and data. Engineers use the layers as a shared language and as a checklist for troubleshooting from the bottom up.30 min
4. The TCP/IP model and encapsulationThe TCP/IP model is the model the internet actually runs on. It has 4 layers (or 5, when the bottom layer is split into data link and physical), and it maps neatly onto OSI. As data goes down the layers, each layer adds its own header: this is encapsulation. The receiver removes the headers in reverse order: de-encapsulation.30 min
5. TCP, UDP and port numbersThe transport layer delivers data to the right program using port numbers. TCP is reliable: it sets up a connection with a three-way handshake, numbers every byte, and resends what is lost. UDP is simple and fast with no guarantees, which suits voice, video and DNS. Well-known ports such as 22 for SSH, 53 for DNS and 443 for HTTPS must be learnt by heart.35 min

How data moves inside a LAN: the cables and fibre that carry it, the Ethernet frame and its MAC addresses, how a switch learns and forwards, how ARP finds a MAC address and when traffic goes to the default gateway, and your first steps on the Cisco IOS command line. After this module you can choose the right cable, read a MAC address, predict what a switch does with a frame, explain ARP and ping results, and give a new Cisco switch a basic, saved configuration.

1. Cables, fibre and Ethernet standardsMost office networks use UTP copper cable with RJ45 plugs, up to 100 metres per run. Cat5e handles 1 Gbps, Cat6a handles 10 Gbps over the full 100 metres. Fibre carries light instead of electricity, so it goes much further and ignores electrical noise; single-mode fibre goes the furthest. Standard names such as 1000BASE-T tell you the speed and the medium.30 min
2. Ethernet frames and MAC addressesAn Ethernet frame carries a packet across one link. It has a destination MAC address, a source MAC address, a type field, the data (46 to 1500 bytes) and a checksum called the FCS. A MAC address is 48 bits, written as 12 hexadecimal digits; the first half (the OUI) names the maker. Speed and duplex must match on both ends of a link, or it becomes slow and full of errors.30 min
3. How a switch learns and forwardsA switch builds a MAC address table by reading the source MAC of every frame it receives and noting the port. To forward, it looks up the destination MAC: if it knows the port, it sends the frame only there; if not, or for a broadcast, it floods the frame out of every other port. Entries that are not used for 300 seconds (the Cisco default) are removed.25 min
4. ARP, the default gateway and pingTo send a frame, a PC needs the MAC address that goes with an IP address. ARP finds it: a broadcast request asks "who has this IP?" and the owner sends a unicast reply. If the destination is on another network, the PC sends the frame to its default gateway (router) instead. Ping uses ICMP echo request and echo reply to test whether a host can be reached.30 min
5. The Cisco IOS command lineCisco switches and routers are configured through the IOS command line, over a console cable or SSH. You move through modes: user EXEC (>), privileged EXEC (#), global configuration and interface configuration. Changes go into the running-config in RAM at once, and are lost on reboot unless you copy them to the startup-config in NVRAM.35 min

IPv4 addresses from the bits up: binary and decimal, how an address splits into a network part and a host part, the special and private ranges, subnet masks and prefix lengths, and how to find the network, broadcast and usable host range of any address. Every topic has small Python or JavaScript tools you build yourself. After this module you can read any IPv4 address with its mask, work out its subnet by hand and with Python, and spot the addressing mistakes that break real networks.

1. Binary and decimal for networkingComputers store everything as bits, ones and zeros. An IPv4 address is 32 bits, written as four groups of 8 bits called octets, and each octet is a number from 0 to 255. If you know the place values 128, 64, 32, 16, 8, 4, 2 and 1, you can convert any octet between decimal and binary in your head, and that skill is the base of all subnetting.25 min
2. IPv4 address structure and special rangesAn IPv4 address is 32 bits split into a network part, which says which network the device is on, and a host part, which says which device it is. The old classes A, B and C are history now, but you still need to know them. Some ranges are special: the private ranges 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16, loopback 127.0.0.0/8, APIPA 169.254.0.0/16 and multicast 224.0.0.0/4.30 min
3. Subnet masks, prefix length and wildcard masksA subnet mask is 32 bits: ones over the network part and zeros over the host part. You can write it in dotted decimal (255.255.255.0) or as a prefix length (/24), the number of one bits. A device finds its network by doing a bitwise AND of its address and mask. A wildcard mask is the opposite of a subnet mask and is used in Cisco ACLs and OSPF.30 min
4. Network, broadcast and usable host rangeIn every subnet, the address with all host bits 0 is the network address and the one with all host bits 1 is the broadcast address. Everything in between is the usable host range, and there are 2^h − 2 usable hosts, where h is the number of host bits. The block size method (256 minus the interesting mask octet) lets you find all of this in seconds without writing binary.35 min
5. Validating addresses and checking the same subnetA valid IPv4 address has exactly four parts, each a whole number from 0 to 255, with no letters, spaces or leading zeros. Two hosts are in the same subnet when their addresses give the same network after ANDing with the same mask. Many real outages come from small addressing slips: a wrong mask on one PC, a host address typed as a network, or two devices with the same IP.25 min

Hands-on subnetting: splitting a network into equal subnets, VLSM plans that waste few addresses, timed drills with a cheat table and route summarisation, and then IPv6: why it exists, how to write and shorten its 128-bit addresses, the address types, EUI-64, SLAAC, DHCPv6 and NDP. Every topic has Python or JavaScript tools you write and test yourself. After this module you can subnet any IPv4 block quickly and correctly, design a VLSM plan for a real site, summarise routes, and read, shorten and configure IPv6 addresses on a Cisco router.

1. Subnetting a network into equal subnetsSubnetting means splitting one network into several smaller ones by borrowing host bits and using them as subnet bits. Borrowing s bits gives 2^s subnets, and the h host bits that are left give 2^h − 2 usable hosts in each. Smaller subnets mean smaller broadcast domains, better security between groups, and a tidier network.35 min
2. VLSM: subnets of different sizesVLSM (Variable Length Subnet Masking) lets you cut one block into subnets of different sizes, so a 100-host lab, a 25-host office and a 2-host router link each get just what they need. Allocate the largest subnet first, then the next largest, each starting right after the previous one. This keeps every subnet on a valid boundary and leaves the free space in one tidy piece.35 min
3. Subnetting drills for exam speedSubnetting gets fast only with practice. Memorise one cheat table (prefix, mask, block size, hosts), follow the same six steps every time, and work through drills until each takes under a minute. Route summarisation is the reverse skill: joining several networks into one shorter prefix that covers them all.35 min
4. IPv6 addresses: format and shortening rulesIPv6 was created because IPv4 ran out of addresses. An IPv6 address is 128 bits, written as eight groups of four hexadecimal digits called hextets. You shorten it by dropping leading zeros in each hextet and by replacing the longest run of all-zero hextets with :: once. Most LANs use a /64 subnet, and a site often gets a /48 with 16 bits for subnet IDs.30 min
5. IPv6 address types, EUI-64, SLAAC and NDPIPv6 has global unicast addresses (2000::/3), link-local addresses (fe80::/10) on every interface, unique local addresses (fd00::/8 in practice), loopback ::1, the unspecified address ::, multicast (ff00::/8) and anycast, but no broadcast. Devices can build their own address with SLAAC, using EUI-64 or a random interface ID, or get one from DHCPv6. NDP, built on ICMPv6, replaces ARP.35 min

How a switched network is split into VLANs, how trunks carry many VLANs on one cable with 802.1Q tags, how traffic moves between VLANs through a router or a layer 3 switch, how CDP and LLDP show you who is connected where, and how to read interface status and error counters. After this module you can configure VLANs, access ports, trunks and inter-VLAN routing on Cisco switches, map a network with CDP or LLDP, and diagnose common port problems such as err-disabled ports and duplex mismatches.

1. VLANs: what they are and why we use themA VLAN (virtual LAN) is a group of switch ports that act like their own separate switch. Broadcasts stay inside the VLAN, so one physical switch can safely carry staff, guest and camera traffic apart from each other. You create a VLAN with vlan 10, put a port in it with switchport access vlan 10, and check the result with show vlan brief.30 min
2. Trunks and 802.1Q taggingA trunk is a link that carries many VLANs at once. Each frame gets a 4-byte 802.1Q tag holding its VLAN number, so the switch at the other end knows which VLAN it belongs to. Frames in the native VLAN travel untagged, so the native VLAN must match on both ends. Use switchport mode trunk, control the VLANs with switchport trunk allowed vlan (and do not forget the add keyword), and verify with show interfaces trunk.30 min
3. Inter-VLAN routingDevices in different VLANs are in different subnets, so a layer 3 device must route between them. Router-on-a-stick uses one router port as a trunk, with one subinterface per VLAN (encapsulation dot1Q 10 and an IP address). A layer 3 switch does the same job faster with SVIs (interface vlan 10) after ip routing. Each SVI or subinterface address is the default gateway for its VLAN.35 min
4. CDP and LLDP: discovering neighboursCDP (Cisco, on by default) and LLDP (an open IEEE standard) let a device announce its name, model, port and address to the devices directly connected to it. show cdp neighbors and show lldp neighbors tell you what is plugged into each port, which is how engineers draw or check a network diagram. Because they reveal details to anyone connected, turn them off on ports that face users or outside networks.25 min
5. Switch management and interface troubleshootingA layer 2 switch gets a management IP address on an SVI and a default gateway with ip default-gateway, so you can reach it remotely. To troubleshoot a port, read its status (up/up, down/down, administratively down, err-disabled) and its error counters. CRC errors, runts and late collisions usually point to bad cabling or a duplex mismatch, which you fix by setting speed and duplex the same on both ends.30 min

Why redundant switch links create deadly layer 2 loops, how the Spanning Tree Protocol elects a root bridge and blocks just enough ports to break every loop, how classic STP, RSTP and Cisco's per-VLAN versions converge, how PortFast, BPDU Guard, Root Guard and Loop Guard protect the tree, and how EtherChannel bundles several links into one. After this module you can predict the root bridge, root ports and blocked ports of a small network, configure Rapid PVST+ with a chosen root, protect access ports, and build and verify an LACP EtherChannel.

1. Why layer 2 loops are deadlyWe connect switches with extra links so the network survives a cable cut, but extra links create loops. Ethernet frames have no TTL, so a broadcast caught in a loop circles forever and multiplies, causing a broadcast storm, a confused MAC address table and duplicate frames. The Spanning Tree Protocol (STP, IEEE 802.1D) fixes this by blocking just enough ports to leave a loop-free tree, and unblocking them if an active link fails.20 min
2. Root bridge election, root ports and designated portsEvery switch has a bridge ID: a priority (32768 by default, plus the VLAN number) followed by its MAC address. The lowest bridge ID becomes the root bridge. Every other switch picks one root port, its cheapest path to the root, using port costs (1 Gbps = 4, 100 Mbps = 19). Each link gets one designated port, and every port that is neither root nor designated is blocked.35 min
3. STP port states, RSTP and Rapid PVST+Classic STP moves a port through blocking, listening and learning before forwarding, using timers (hello 2 s, forward delay 15 s, max age 20 s), so it takes 30 to 50 seconds to react to a change. RSTP (802.1w) uses only discarding, learning and forwarding, adds alternate and backup roles, and converges in about a second. Cisco runs one tree per VLAN: PVST+ or Rapid PVST+. You pick the root with spanning-tree vlan 10 root primary or a priority such as 24576.30 min
4. Protecting spanning tree: PortFast, BPDU Guard, Root Guard and Loop GuardPortFast makes a port to an end device forward at once instead of waiting 30 seconds. BPDU Guard err-disables a port the moment a BPDU arrives on it, which stops loops and rogue switches on user ports. Root Guard stops another switch from becoming root through a port, and Loop Guard stops a port from forwarding just because BPDUs stopped arriving. An err-disabled port comes back with shutdown and no shutdown, or automatically with errdisable recovery.25 min
5. EtherChannel: bundling linksEtherChannel bundles 2 to 8 physical links into one logical link (a port-channel), so spanning tree sees one link and all members carry traffic. LACP (IEEE 802.3ad, now 802.1AX) uses active and passive modes, Cisco's PAgP uses desirable and auto, and on forces the bundle without negotiation. All members must match in speed, duplex and VLAN settings. Traffic is spread by a hash, so one flow always uses one member link.30 min

How a router decides where every packet goes: the routing table, longest prefix match, administrative distance and metrics, static and default routes, the OSPF link-state protocol from concepts to configuration, and first hop redundancy with HSRP. After this module you can read show ip route with confidence, build static and floating static routes, configure and troubleshoot single-area OSPFv2, and give a LAN a gateway that survives a router failure.

1. How a router forwards: the routing tableA router reads the destination IP address of each packet and looks it up in its routing table. If several routes match, the most specific one (the longest prefix) wins. When two sources offer the same prefix, the router trusts the one with the lower administrative distance, and inside one source it picks the lower metric.30 min
2. Static and default routesA static route is a route you type by hand: "to reach this network, send packets to this next hop". A default route (0.0.0.0/0) catches everything the router has no better route for. A floating static route has a higher administrative distance so it is used only when the main route disappears. Always remember that the reply needs a route back too.30 min
3. OSPF concepts: link state, areas and neighboursOSPF (Open Shortest Path First) is a link-state routing protocol: every router learns a full map of the area and runs the SPF (Dijkstra) algorithm to find the cheapest path to every network. The cost of a link is reference bandwidth divided by interface bandwidth. Routers become neighbours by exchanging hellos and move through states up to Full. On Ethernet, a DR and BDR reduce the flooding.35 min
4. Configuring and verifying single-area OSPFStart OSPF with router ospf 1, set a router ID, then enable it on interfaces with network commands (using wildcard masks) or with ip ospf 1 area 0 on each interface. Make LAN interfaces passive, share a default route with default-information originate, and verify with show ip ospf neighbor, show ip ospf interface brief and show ip route ospf. Most neighbour problems come from mismatched settings.35 min
5. First hop redundancy: HSRP, VRRP and GLBPA PC has only one default gateway. If that router fails, the PC is cut off even when a second router is ready. First hop redundancy protocols let two or more routers share a virtual IP and virtual MAC address, so the gateway keeps working when one router dies. HSRP is Cisco's protocol, VRRP is the open standard, and GLBP also shares the load.25 min

The services that make an IP network usable every day: DHCP hands out addresses, DNS turns names into addresses, NAT lets a whole office share one public IP, NTP keeps clocks right, SNMP and syslog let you monitor devices, and QoS keeps voice calls clear when links are busy. After this module you can configure a Cisco router as a DHCP server and relay, set up PAT and static NAT, point devices at NTP and syslog servers, read DNS records and Cisco log messages, and explain DSCP markings and queuing.

1. DHCP: automatic addressesDHCP (Dynamic Host Configuration Protocol) gives a device its IP address, mask, default gateway and DNS servers automatically when it joins a network. It works in four steps: Discover, Offer, Request, Acknowledge (DORA). A Cisco router can be the DHCP server, and ip helper-address relays requests to a server on another subnet.30 min
2. DNS: names to addressesDNS (Domain Name System) turns names like www.irctc.co.in into IP addresses. A recursive resolver asks the root servers, then the top-level domain servers, then the authoritative server for the domain, and caches the answer for its TTL. Records have types such as A, AAAA, CNAME, MX, NS, PTR, TXT and SOA. DNS uses UDP and TCP port 53.30 min
3. NAT and PATNAT (Network Address Translation) lets devices with private addresses reach the internet by swapping their address for a public one at the router. Static NAT maps one private address to one public address, dynamic NAT uses a pool, and PAT (NAT overload) lets hundreds of devices share one public IP by using different port numbers. Your home router and your mobile operator both do it.35 min
4. Management services: NTP, SNMP, syslog and TFTPNTP keeps every device's clock correct, which matters for logs, certificates and logins. SNMP lets a monitoring server read values from devices and receive alerts (traps). Syslog sends log messages, each with a severity from 0 (emergency) to 7 (debugging), to a central server. TFTP and FTP move IOS images and configuration backups.30 min
5. QoS basics: keeping voice and video clearQoS (Quality of Service) decides which traffic goes first when a link is busy. Traffic is classified and marked (CoS in the 802.1Q tag, DSCP in the IP header; EF 46 for voice), then queued so that voice gets a strict priority queue (LLQ) and other classes get guaranteed shares. WRED drops some packets early to avoid congestion, and policing or shaping keeps traffic to a contracted rate.30 min

How networks are attacked and, more importantly, how they are defended: the key security words, the CIA triad, AAA with RADIUS and TACACS+, 802.1X, hardening Cisco devices with SSH and strong secrets, access control lists, Layer 2 protections (port security, DHCP snooping, Dynamic ARP Inspection) and firewalls, IPS and VPNs. Everything is taught at CCNA level, for defence, and practised only on your own lab. After this module you can explain common threats and their fixes, secure device access, write and place standard and extended ACLs, protect switch access ports, and describe where firewalls, IPS and IPsec VPNs fit in a network.

1. Security basics: threats, CIA and AAANetwork security protects the confidentiality, integrity and availability (the CIA triad) of data and services. You defend in layers: trained users, locked rooms, strong logins, filtered traffic and monitoring. AAA (authentication, authorisation, accounting) controls who logs in, what they may do and what they did, usually with a RADIUS or TACACS+ server.30 min
2. Securing device access: secrets and SSHA router or switch is only as safe as the way people log in to it. Use enable secret (hashed) instead of enable password, personal usernames with login local, and SSH version 2 instead of Telnet on the VTY lines. Add timeouts, login delays, a warning banner, and shut down unused ports and services.30 min
3. Access control lists (ACLs)An access control list (ACL) is an ordered list of permit and deny rules that a router checks against each packet. Standard ACLs match only the source address; extended ACLs match protocol, source, destination and ports. The first matching rule wins, and an invisible "deny any" sits at the end. You apply an ACL to an interface in one direction with ip access-group.35 min
4. Layer 2 security: port security, DHCP snooping, DAIAccess switch ports are where users, and sometimes attackers, plug in. Port security limits which MAC addresses may use a port. DHCP snooping lets only trusted ports send DHCP server replies and builds a table of who got which address. Dynamic ARP Inspection uses that table to drop fake ARP messages. Disabling DTP and changing the native VLAN stops VLAN hopping.35 min
5. Firewalls, IPS and VPNsA firewall controls traffic between zones such as inside, outside and DMZ. A stateful firewall remembers connections, so replies to inside users come back in while unrequested traffic is blocked. An IPS sits in the traffic path and blocks attacks it recognises; an IDS only watches and alerts. VPNs carry private traffic safely across the internet: site-to-site IPsec joins offices, and remote-access VPNs connect single users.30 min

How Wi-Fi works and how companies build it: radio basics, the 2.4, 5 and 6 GHz bands, the 802.11 standards from 802.11b to Wi-Fi 7, SSIDs, BSS and ESS, and CSMA/CA. Then the architectures (autonomous, controller-based with CAPWAP, cloud-managed), AP modes, Wi-Fi security from WEP to WPA3, and configuring and troubleshooting a WLAN on a Cisco Wireless LAN Controller. After this module you can choose channels and bands, explain split-MAC and CAPWAP, pick the right security for staff and guest networks, configure a WLAN on a WLC step by step, and work through common Wi-Fi complaints.

1. Wi-Fi basics: radio, bands and standardsWi-Fi sends data as radio waves in the 2.4 GHz, 5 GHz and 6 GHz bands. In 2.4 GHz only channels 1, 6 and 11 do not overlap; 5 GHz and 6 GHz have many more channels. The 802.11 standards (b, a, g, n, ac, ax, be) set the speeds and bands. Clients join an SSID through an access point, and they share the air using CSMA/CA.35 min
2. WLAN architectures, CAPWAP and AP modesSmall sites can use autonomous APs, each configured on its own. Larger networks use lightweight APs managed by a Wireless LAN Controller (WLC), which talk to it over CAPWAP tunnels (UDP 5246 for control, 5247 for data); this split of work is called split-MAC. Cloud-managed APs such as Meraki are run from a web dashboard. APs can work in modes such as local, FlexConnect, monitor and sniffer.30 min
3. Wi-Fi security: WPA2, WPA3 and guest networksAnyone nearby can receive Wi-Fi signals, so encryption and authentication are essential. WEP and the first WPA are broken or outdated; use WPA2 with AES, or better, WPA3. Personal mode uses a shared passphrase (PSK, or SAE in WPA3); Enterprise mode gives each user their own login through 802.1X and a RADIUS server. Guest networks should be separate, isolated and limited to the internet.30 min
4. Configuring a WLAN on a WLC and troubleshooting Wi-FiOn a Cisco WLC you build a WLAN in a few steps: create a dynamic interface for the VLAN, create the WLAN with its profile name and SSID, map it to that interface, choose WPA2 or WPA3 security (Personal or Enterprise with a RADIUS server), pick a QoS profile and enable it. When Wi-Fi fails, check in order: association, authentication, IP address, then signal and channels.35 min

Networks are now too big to configure one device at a time. This module explains why automation matters, how controller-based networking (SDN) splits the work into planes and APIs, how REST APIs and JSON let programs talk to network devices, how Ansible, Puppet, Chef and NETCONF keep configurations consistent, and how virtual machines, VRFs and cloud networks (VPCs, subnets, gateways, security groups) work. After this module you can explain SDN and intent-based networking, read and validate the JSON a network API returns, generate device configuration from a template in Python, and plan the subnets of a cloud VPC.

1. Why automate: SDN and controller-based networkingConfiguring hundreds of devices by hand is slow and full of typing mistakes. Every network device has three planes: the data plane forwards packets, the control plane decides where they go, and the management plane is how people and programs configure it. Software-defined networking (SDN) moves control and management into a central controller that apps talk to through northbound APIs and that talks to devices through southbound APIs.30 min
2. REST APIs and JSONA REST API lets a program read and change things on a controller or device by sending HTTP requests to URLs. The HTTP method says what to do (GET reads, POST creates, PUT or PATCH updates, DELETE removes), and the status code in the reply says how it went. The data travels as JSON: objects in curly braces, arrays in square brackets, and text always in double quotes.35 min
3. Configuration management: Ansible, Puppet, Chef and NETCONFConfiguration management tools keep many devices in the state you wrote down, instead of you typing the same lines on each one. Ansible is agentless and pushes changes over SSH using YAML playbooks; Puppet and Chef use an agent on each device that pulls its configuration from a server. NETCONF and RESTCONF are standard protocols that change device configuration using YANG data models.30 min
4. Virtualisation, VRFs and cloud networkingA hypervisor lets one physical server run many virtual machines, connected by a virtual switch. VRFs give one router several separate routing tables. In the cloud you build your own private network (a VPC or VNet) with subnets, route tables, an internet gateway, a NAT gateway, and firewalls called security groups (stateful) and network ACLs (stateless).35 min

The last module turns everything you have learnt into two practical skills: finding faults calmly and quickly, and passing the CCNA 200-301. It covers a step-by-step troubleshooting method and its approaches (top-down, bottom-up, divide and conquer and more), the tools and show commands that reveal each common fault, how the CCNA exam is built and booked, a 12 to 16 week study plan based on this course, and the jobs, salaries and next certifications that follow. After this module you can troubleshoot a broken network in a structured way, plan and sit the CCNA with confidence, and prepare for your first networking interview.

1. A structured troubleshooting methodGood troubleshooting is a method, not luck. You define the problem, gather facts, analyse them, eliminate what is working, test one likely cause at a time, fix it, and write down what happened. Approaches such as bottom-up, top-down and divide and conquer tell you where to start, and good documentation and baselines make every step faster.25 min
2. Troubleshooting tools and common faultsA few tools find most faults. ping tests reachability, traceroute shows the path and where it stops, and ipconfig, ip addr and nslookup check a host. On Cisco devices, show ip interface brief, show vlan brief, show interfaces trunk, show ip route and show ip ospf neighbor reveal most problems. Learn the symptom of each common fault, such as a wrong gateway, a wrong VLAN or a DNS failure, and you can find it in minutes.35 min
3. The CCNA 200-301 exam and your study planThe CCNA (Cisco Certified Network Associate) is earned by passing one exam, 200-301, which lasts 120 minutes and covers six domains from network fundamentals to automation. You book it through Pearson VUE, at a test centre or online, and it stays valid for three years. A 12 to 16 week plan built on this course, with daily subnetting practice and lots of Packet Tracer labs, is a realistic way to pass.30 min
4. Networking careers in India and beyondNetworking jobs start with IT support or NOC roles and grow into network administrator, network engineer, and specialist roles in security, cloud and automation. Pay in India starts low for freshers (often ₹2.5–5 LPA for NOC L1) and rises with experience and certifications. ISPs, IT services companies, system integrators, banks, data centres and managed service providers all hire. A CCNA, a homelab and the ability to explain your work clearly in an interview make the biggest difference.25 min