CCNA Cheatsheet – GeeksforGeeks



A CCNA certification proves you could have the competencies wanted to navigate an ever-changing IT panorama. CCNA exams cowl community fundamentals, IP providers, safety fundamentals, automation, and programmability. Designed for agility and flexibility, CCNA proves you could have the talents wanted to handle and optimize in the present day’s most superior networks. CCNA coaching programs and exams are the muse for advancing your profession in any route. A Cisco certification resides proof of the requirements and rigor your group acknowledges and trusts to fulfill and exceed market calls for. Here’s a cheat sheet for CCNA Examination.

Community Fundamentals:

Networking Units Utilized in CCNA: 

Names of units use in CCNA Description

A router is a community system that forwards knowledge packets between pc networks. A router receives a packet from an enter port, checks its header, performs  primary capabilities corresponding to checksum checking, appears to be like up the suitable output port’s routing desk, drops the packet, and so forth. Ahead the packet to the output port.


A swap is a community system used to divide a community into totally different subnets referred to as subnets or LAN segments. Filters and forwards packets between LAN segments based mostly on MAC deal with. A swap establishes a brief connection between a supply and vacation spot for communication and terminates the connection when the dialog ends. It additionally offers full bandwidth for community visitors going to and from units on the similar time, decreasing collisions.


A firewall is a {hardware} or software-based community safety system that screens all incoming and outgoing visitors and accepts, denies, or drops particular visitors based mostly on an outlined set of safety guidelines.


Intrusion prevention methods are also referred to as intrusion detection and prevention methods. It is a community safety utility that screens community or system exercise for malicious exercise. The primary perform of an intrusion prevention system is to establish malicious exercise, acquire and report details about that exercise,  and try to dam or cease it.

Entry factors

It is a community system that enables your system to hook up with a wired community.  Entry factors are used to construct WLANs (Wi-fi Native Space Networks). It’s generally utilized in massive workplaces and buildings with rising companies.


the community controller is a centralized programmable automation level that allows you to handle, configure, monitor, and troubleshoot your digital community infrastructure, along with manually configuring community units. An extensible server position that gives Run the service. It acts as an interface between your retailer and your community infrastructure.


Endpoint Safety Management is a software program know-how that facilitates the popularity and operation of non-public laptops to achieve entry to the company group. This enables group admins to limit constructive web sites to particular clients, thus adhering to their group’s guidelines and necessities relating to the additive in query. Endpoint safety management constructions embody digital non-public VPN purchasers, working methods, and up-to-date antivirus software program.


Servers are computer systems devoted to a selected goal, and in contrast to desktop computer systems, these computer systems are constructed to be sturdy, long-lived, and long-running in comparison with desktop PCs.

Community Topology Architectures:

Traits of community topology Description

LAN stands for Native Space Community. That is a pc community that covers a comparatively small space. B. Inside a constructing or campus as much as a number of kilometers in dimension.


MAN stands for Metropolitan Space Community. It’s a pc community that connects many LANs into a bigger community in order that pc assets will be shared. Such a community covers a bigger space than a LAN however is smaller than a WAN  designed to span a whole metropolis.


WAN stands for Broad Space Community. It’s a pc community consisting of two or extra LANs or MANs overlaying a big geographical space.


A spine-leaf structure is an information heart community topology that consists of two switching layers: backbone and leaf.

Small workplace/residence workplace (SOHO)

SOHO stands for Small Workplace/Residence Workplace Community. Immediately, many aspiring entrepreneurs and small enterprise house owners desire to work at home or keep a small workplace.

Cloud storage

Cloud storage merely shops knowledge over the web on cloud-based servers. As soon as your knowledge is saved within the cloud, you’ll be able to entry it anyplace over the web from a number of units.

Bodily Interface and Cabling Sorts:

Interfaces and cabling Description
Single-mode fiber cable

SMF (Single-Mode Fibers) are fiber cables designed to hold solely single-mode gentle, which is the transverse mode. They’re used for long-distance transmission of alerts.

multi-mode fiber cable

Multimode fiber optic cable is a kind of fiber optic cable that transmits knowledge by means of a bigger diameter core, permitting the common single-mode transceiver to hold a number of modes of sunshine.

copper wire

Copper cables use electrical alerts to transmit knowledge between networks. There are three varieties of copper cable: coaxial cable, unshielded twisted pair, and shielded twisted pair. Coax degrades over lengthy distances


Ethernet is probably the most broadly used LAN know-how outlined by the IEEE 802.3 normal. The rationale for its vast applicability is that Ethernet is straightforward to grasp, straightforward to implement and keep, and permits cheap community implementation. Moreover, Ethernet presents flexibility when it comes to allowed topologies.


Energy Over Ethernet (POE) is a method used for constructing wired Ethernet native space networks (LANs) which use Ethernet knowledge cables as a substitute of regular electrical energy cords and wiring to hold {the electrical} present required to function every system.

IP Addressing:

Lessons of IP Addresses:

Class First 5 bits in binary First Octet vary
A 0xxxx 0-127 (really 1-126 as a result of 0 and 127 are reserved
B 10xxx 128-191
C 110xx 192-223
D 1110x 224-239
E 1111x 240-254

Reserved IP Addresses:

Deal with What it represents The place can or not it’s used
Community deal with of all 0s

Stands for “this community”. For instance,

Ship a broadcast message to the community.

Community deal with of all 1s

Represents “all networks”.

Ship a broadcast message to all networks.

Node deal with of all 0s

Represents a community deal with or all hosts on a community. Instance or

Routers route visitors based mostly on community addresses.

Node deal with of all 1s

It represents all hosts on the community and can also be referred to as the printed deal with. Instance or

Used to ship broadcasts to all hosts on the community.

Complete deal with of 0s

Stands for “any community”.

Utilized by routers to set a default route.

Complete IP set to all 1s.

Stands for all hosts in community.

Used to ship/broadcast messages

Stands for loopback deal with which is actually the host itself

Ship visitors from the host to itself. Use this deal with in your browser to hook up with the online server operating on the host itself.

Legitimate Hosts Addresses in Every Subnet:

Variable Size Subnet Masks (VLSM):

Troubleshooting IP Addressing:

Troubleshooting Description
Packet Web Grouper (PING)

Ping is likely one of the mostly used utilities for troubleshooting addressing and connectivity issues. This utility is obtainable for many working methods, together with Cisco units, and will be accessed by means of the command line interface utilizing the ping command. Checks if the goal host is up utilizing the ICMP protocol.


Traceroute is one other widespread utility  obtainable on all working methods. On some working methods, the utility will be accessed utilizing the tracert or traceroute instructions within the CLI. It’s used to seek out every hop between a supply host and a vacation spot host, serving to to see the trail taken by a packet.

IP config

On Home windows machines, all this data is displayed within the output of the ipconfig /all command. On Unix-based methods, this data will be seen utilizing the ifconfig command.

ARP Tables

This desk incorporates the MAC and IP deal with associations realized by the system. On most working methods, the ARP desk will be seen with the arp –a command. On  Cisco units, you’ll be able to view the arp desk  utilizing the present ip arp command.

Port Safety:

Switches study MAC addresses as frames are forwarded by means of swap ports. Port safety permits you to restrict the variety of MAC addresses that may be realized on a port, configure static MAC addresses, and set penalties if that port is utilized by unauthorized customers. Customers can prohibit, shutdown, or shield port safety instructions.

Port-Safety Phrases of Violation:

Time period Definition
shield To Drops packets with no alert
prohibit To Drops packets and increment security-violation depend
shutdown To Shuts down the port (default)

Troubleshooting Port Safety:

Command Description
# present port-security [interface g1/1] port standing, violation mode, max/complete MACs,…
# present port-security deal with Safe MACs on ports.
# present errdisable restoration Verify if auto restoration is enabled. Disabled by default.

Configure VLANs:

Digital LAN (VLAN) is an idea that enables units to be logically partitioned at layer 2 (knowledge hyperlink layer). Layer 3 units usually share a broadcast area, however the idea of VLANs can be utilized to divide the printed area with switches.

Layer2 Change VLAN Config:

Layer3 Change VLAN Config:

Router (on a Stick) VLAN Config:

Troubleshoot VLANs on a Change:


STP (Spanning Tree Protocol):

Spanning Tree Protocol (STP) prevents body loops by placing interfaces on a swap right into a forwarding or blocking states.

Troubleshoot STP:


EtherChannel is a port hyperlink aggregation know-how that teams a number of bodily port hyperlinks into one logical hyperlink. Used to offer high-speed connectivity and redundancy. As much as eight hyperlinks will be aggregated into one logical hyperlink.

Troubleshoot Etherchannel:

Configure a Serial:

The pace of the Layer 1 connection is decided by the CSU/DSU. DTE (Information Terminal Tools)  and DCE (Information Communications Tools) cables are utilized in labs with out an exterior CSU/DSU.

Command Description
(config)# interface serial 1/0 To Configure interface serial 1/0
(config-if)# clock price 128000 To Set clock price for DCE router facet to 128 kbps
(config)# present controllers serial 1/0 To Confirm clock price on serial interface 1/0

Entry Management Lists (ACLs):

Default masks for default ACL:

Interface ACLs:

Troubleshooting ACLs:

Community Deal with Translation (NAT):

Community Deal with Translation (NAT) is the method of translating a number of native IP addresses into a number of world IP addresses, or vice versa, in an effort to present Web entry to native hosts. It additionally performs port quantity translation. H. Masks the host’s port quantity with one other port quantity in packets routed to the vacation spot.

Time period Definition
inside native IP addresses assigned to hosts within the community aren’t routable
inside world A routable IP deal with assigned by your Community Data Middle or ISP
exterior native The IP deal with of the distant host seen on the community will not be routable
exterior world The owner-assigned IP deal with of the distant host, routable


SNAT, because the title suggests, is a method for usually translating the supply IP deal with when connecting from a non-public IP deal with to a public IP deal with. Maps the originating consumer IP deal with within the request to a rework outlined on the BIG-IP system. That is the most typical type of NAT and is used when inner hosts have to provoke classes with exterior or public hosts.


DNAT, because the title proposes, is a method for principally translating vacation spot IP addresses when connecting from a public IP deal with to a non-public IP deal with. It’s usually used to redirect packets destined for a selected IP deal with on one host or a selected port on an IP deal with to a different deal with (almost definitely one other host).

Port Deal with Translation (PAT):

Port deal with translation is carried out in routers. So the IP packet obtained by the router incorporates a non-public IP and a port quantity (supplied by the pc), so the router replaces the non-public IP with the general public IP of the router and a selected port is assigned to this connecting system.

DHCP (Dynamic Host Management Protocol):

Dynamic Host Configuration Protocol (DHCP) is an utility layer protocol used to offer:

  1. Subnet Masks (Choice 1 – e.g.,
  2. Router Deal with (Choice 3 – e.g.,
  3. DNS Deal with (Choice 6 – e.g.,
  4. Vendor Class Identifier (Choice 43 – e.g., ‘unifi’ = ##the place unifi = controller)

Troubleshooting DHCP:

HSRP (Scorching Standby Router Protocol):

HSRP (Scorching Standby Router Protocol) is a CISCO proprietary protocol that gives redundancy for a neighborhood subnet. In HSRP, two or extra routers create the phantasm of a digital router.

Troubleshooting HSRP:

Command Description
# present standby HSRP Teams, their VIPs, state, lively router, standby router, preemption.

Service Stage Agreements (SLAs):

Service Stage Agreements (SLAs) are efficiency constraints negotiated between the cloud service supplier and the client. Beforehand, in cloud computing, all service stage agreements have been negotiated between the client and the buyer of the service. Immediately, with the appearance of main utility-style cloud suppliers, most service stage agreements are standardized till clients turn into main customers of cloud providers. cloud.

Troubleshooting SLAs:

Telnet / Console:

TELNET stands for Terminal Community. It’s a sort of protocol that enables a pc to hook up with a neighborhood pc. It’s used as the usual TCP/IP protocol for the digital terminal service supplied by ISO. The pc that initiates the connection known as the native pc. 


SSH (Safe Shell) is an entry identifier used within the SSH protocol. In different phrases, it’s a cryptographic community protocol used to transmit encrypted knowledge over a community. It permits you to hook up with a server or servers with out having to recollect or enter your password for every system that should join remotely from one system to a different.

TACACS+ Protocol:

TACACS+, which stands for Terminal Entry Controller Entry Management Server, is a safety protocol used throughout the AAA framework to offer centralized authentication for customers who want to entry the community.

Easy Community Administration Protocol (SNMP):

SNMP is an utility layer protocol that makes use of UDP port quantity 161/162. SNMP is used to observe the community, detect community failures, and generally even to configure units remotely.

CDP – Cisco Discovery Protocol:

CDP permits customers to make use of quite a lot of show instructions that enable them to view related system data corresponding to native port data, distant port data, hostname, system platform, and so forth.

Hyperlink Layer Discovery Protocol (LLDP):

It’s an open layer 2 protocol compliant with the IEEE (802.1AB) normal. LLDP is an open supply different to CDP (Cisco Discovery Protocol), which can also be a tool discovery protocol that runs solely on layer 2 (knowledge hyperlink layer)  on Cisco-manufactured units (routers). routers, bridges, entry servers, and switches).

Level-to-Level Protocol (PPP):

Level-to-Level Protocol (PPP) is mainly a set of uneven protocols for various connections or hyperlinks that don’t present frames, i.e., uncooked bit pipes. PPP additionally desires different protocols to ascertain connections, authenticate customers, and in addition transport community layer knowledge. PPP will not be a single protocol, however a set of protocols consisting of easy protocols that deal with varied features of Layer 2 point-to-point communication.

Troubleshooting PPP:

Command Description
# present controllers S0/0/0 To Present interface, related sort of cable, clock price
# present interfaces To Present encapsulation, logical bandwidth
# present ppp all To Present session state, auth sort, peer ip and title
# debug ppp authentication To Debug PPP authentication


Routing Data Protocol (RIP) is a dynamic routing protocol that makes use of hop depend as a routing metric to seek out one of the best path between supply and vacation spot networks. It’s a distance vector routing protocol with an AD worth of 120 and operates on the community layer of the OSI mannequin. RIP makes use of port quantity 520.

Troubleshooting RIP:

Command Description
# present ip[v6] protocols Present rip timers, interfaces, networks,
# present ip rip database Routes realized by rip have been used to compile the routing desk
# present ip route Present realized routes
# clear ip route * Do away with all routes


EIGRP (Enhanced Inside Gateway Routing Protocol) is a dynamic routing protocol used to seek out one of the best path between any two Layer 3 units for packet supply. EIGRP works on prime of the community layer protocol of the OSI mannequin and makes use of protocol quantity 88. It makes use of metrics to seek out one of the best path between two Layer 3 units (Layer 3 routers or switches). utilizing EIGRP.

Command Description
# present run | part eigrp To Present EIGRP settings.
# present interfaces g1/1 To Present configured/default bandwidth and delay.
(config-if)# bandwidth To Overwrite bandwidth used for eigrp metric.
(config-if)# delay To Overwrite show used for eigrp metric.
(config)# router eigrp 23 To Add and conf EIGRP AS#23
(config-router)# community To Announce routes to
(config-router)# no shutdown On some iOS variations, it’s off by default.
(config-router)# [no] eigrp router-id To Set Defaults to highest loopback ip
(config-router)# [no] passive-interface g1/2 To Disable EIGRP right here. Ignore incoming pkgs.
(config-router)# [no] passive-interface default To Disable EIGRP on all ifs by default.
(config-router)# maximum-paths To set Default 4, should match, the variety of load-balanced paths.
(config-router)# variance 4 To Set Default 1, Max 4:1 variance for unequal lb.
(config-router)# no auto-summary To Set Don’t summarize a smaller subnet route in a giant one.
# present ip[v6] eigrp neighbors To indicate Neighbor deal with, if, maintain time, uptime, queued pkgs
# present ip[v6] eigrp interfaces [if-name] To Present If, Variety of friends, pending routes, queued pkgs
# present ip[v6] route [eigrp] To ShowRoutes beginning with D have been realized by way of EIGRP
# present ip[v6] eigrp topology [all-links] Topology desk

EIGRP with ipv6:


Open Shortest Path First (OSPF) is a link-state routing protocol used to seek out one of the best path between supply and vacation spot router utilizing its personal shortest path first). OSPF was developed by the Web Engineering Job Pressure (IETF) as one of many Inner Gateway Protocols (IGP), i.e., a protocol geared toward shifting packets inside a big autonomous system or routing area.

Router Sorts:

Time period Definition
Inner Router Checklist All OSPF interfaces in a single space
Spine Router It has a number of OSPF interfaces within the spine
Space Boundary Router (ABR) It has no less than one interface within the spine space and no less than one in one other space
Autonomous System Boundary Router (ASBR) To Injects routes into OSPF by way of redistribution from different routing protocols

OSPF with ipv6 (OSPFv3):

Command Description
(config)# ipv6 unicast-routing To indicate unicast routing by means of ipv6
(config)# ipv6 router OSPF To indicate config of ipv6 on the router
(config-router)# router-id Required if we don’t have any v4 deal with configured.
(config-if)# ipv6 OSPF space Required for OSPFv3.

The community’s command doesn’t exist, and non talked about instructions are the identical.

Troubleshooting OSPF:

Command Description
# present run | sect ospf To run OSPF
# present ip(v6) protocols To indicate ipv6 in OSPF
# present ipv6 ospf To indicate reference bandwidth, router-id, networks, interface per space
# present ip(v6) ospf neighbor To indicate neighbor IDs, IPs, and by way of the interface.
# present ip(v6) ospf neighbor element To indicate dr, bdr, timers, and so forth.
# present interface temporary To indicate admin downlink
# present ip(v6) ospf interface temporary To indicate OSPF enabled interfaces
# present ip(v6) ospf interface g1/1 To indicate OSPF associated Infos for g1/1, passive?
# present ip(v6) route (ospf) To indicate OSPF routes are marked O, present route advert and value