CCNA - Network Fundamentals

What is the command to generate a crypto key from the CLI?

"crypto key generate rsa" and then choose the number of bits that you want to use for the key.

What is the command to view all IPv6 information about the interfaces on a Cisco device?

"show ipv6 interface brief" will give an abbreviated view, and the full command "show ipv6 interface" will give a detailed view.

What command can you use to see the duplex and speed setting of a port?

"show run interface fa0/24" to check the speed and duplex settings for port 24.

What is at Layer 5 of the TCP/IP model, the Application layer?

1) How software communicates with lower-level protocols, such as how a web browser uses HTTP to pull information from a web server.

What are the 3 parts of using the Extended Unique Identifier 64, or EUI-64, to create an IPv6 address?

1) Split the interface's MAC address in half. 2) Insert FFFE between the parts of the split MAC address. 3) Invert the 7th bit of the interface ID.

What is at Layer 4 of the TCP/IP model, the Transport layer?

1) Transmission Control Protocol (TCP). 2) User Datagram Protocol (UDP). 3) Port numbers from 1 to 65,535.

Name 5 functions or features of a Next Generation Firewall, or NGFW.

1) Unified Threat Management, or UTM. 2) A standard firewall. 3) Web filtering. 4) Inline file scanning. 5) Intrusion Prevention System, or IPS.

What is the subnet mask for 192.168.1.0/24?

255.255.255.0

What is the subnet mask for 192.168.1.0/25?

255.255.255.128

What is the subnet mask for 192.168.1.0/26?

255.255.255.192

What is the subnet mask for 192.168.1.0/27?

255.255.255.224

What is the subnet mask for 192.168.1.0/28?

255.255.255.240

What is the subnet mask for 192.168.1.0/29?

255.255.255.248

What is the subnet mask for 192.168.1.0/30?

255.255.255.252

What is the subnet mask for 192.168.1.0/31?

255.255.255.254

What are the 5 standard terminal interface settings when consoling into a Cisco router or switch?

9600 baud, No flow control, Data bits - 8-bit ASCII, No parity bits, and One stop bit.

What are Tier 2 networks sometimes called?

A Collapsed core design, referring to the Distribution layer switches that are the core of the network.

What is a Data center?

A dedicated space designed for computer and telecom equipment. It includes redundant cooling, power, and telecom communications with providers.

What are CRC or input errors often indicative of?

A duplex mismatch where one port is set to half-duplex, and the port it is connected to is set to full-duplex.

What is the initial CLI login that will be met when logging into a Cisco device?

A new login will be in user exec mode and the prompt will be a greater than sign, such as >.

What is Cisco's DNA center?

A single interface that can be used to manage a network, deploy workflows on a network, and automate provisioning and change management throughout a network.

What type of design is often seen in the Data center?

A spine and leaf design that has a high capacity with multiple communication paths that allow for both redundancy and lower latency.

Name 3 devices that commonly use Power over Ethernet, or PoE.

Access points, VoIP phones, and sensors.

What are the 2 types of interfaces that must be configured when using Static NAT?

An Inside interface that faces the LAN, and an Outside interface that faces the Internet.

What is data called at levels 2, 3, and 4 of the TCP/IP model?

At Layer 4, the Transport layer, it is a segment. At layer 3, the Network layer, it is a packet. At layer 2, the Data Link layer, it is a frame.

What 2 things are needed to generate crypto keys to secure an SSH session into a Cisco device?

Both the hostname and the domain name.

What do the show commands do on the Cisco CLI?

Display configuration and other information, such as show running-config, or show run, to show the presently running configuration.

How do you switch the 7th bit of an IPv6 address after it undergoes the EUI-64 transition?

Each of the characters in the IPv6 address is a hexidecimal character made up of only 4 bits, 8, 4, 2, or 1. Take the 1st 2 characters from the address and convert them to their binary equivalent. You will then have 8 total bits, so reverse the 7th bit, then convert back to hexidecimal.

How can a receiving host determine if any packets were missed during transmission?

Each packet has a sequence number, so if any sequence numbers are missing, the receiving host will know that packets were lost.

How many collision domains are there when using switches?

Each port on a switch is its own collision domain, and ports normally work in full-duplex mode. If a port is set to half-duplex, it will open up the possibility of collisions.

What is Fiber to the Home, or FTTH?

Fiber Internet connectivity delivered via Gigabit Passive Optical Networking, or GPON.

One you have a username on a Cisco device, how can you use it to console into that device?

From config mode, enter "line con 0" to start configuring the console connection. On the next line, use the command "login local". The next time you log into that device, you will be prompted for a username and password.

How do you create a domain name from the Cisco CLI?

From config mode, enter the command "ip domain-name aaronpotts.com" to create the domain aaronpotts.com on that device.

How do you set up a console password so anyone using a console cable to access a Cisco device is prompted for a password?

From config mode, enter the command "line console 0" or "line con 0". That will put you into the configuration mode for the first console connection. From there, enter "password cisco" to make the password cisco. On the next line, enter the "login" command.

How can you set a password for all telnet sessions into a Cisco router or switch?

From config mode, enter the command "line vty 0 15" and press Enter. On the next line, enter the command "password" followed by the password. That would put the same password on all 16 telnet interfaces. On the next line, enter the "login" command.

How do you create a username from the Cisco CLI?

From config mode, enter the command "username admin secret " followed by the password that you want to use. That would set the username to admin.

How do you set the type of remote connections on a Cisco device that you want to force to use the crypto key that you generated with the "crypto key generate rsa" command?

From config mode, go to "line vty 0 15" and press Enter. On the next line, use the command "transport input ?" to see the available connections. To use ssh, for example, you would then use the command "transport input ssh". You would then assign an IP address to that interface.

How do you add an IP address to an interface on a Cisco device?

From config mode, go to the interface, such as "int f0/24" so that you are configuring just that interface, and then simply enter the IP address and subnet, such as "ip address 192.168.0.3 255.255.255.0".

How do you set an enable mode password on a Cisco device?

From configure mode, use the command "enable secret" followed by a space and then the password that you want to use.

How do you give a Cisco device a name?

From configure mode, use the command "hostname RTR1" to name the device RTR1.

What does the question mark (?) do when using the Cisco CLI?

Gives help options that are available for whatever status the CLI is in at that time, such as configure mode, a specific interface, etc.

How can you automatically convert an IPv6 address to its EUI-64 format?

Go to the interface that you are going to configure the IPv6 address on and use the command "ipv6 address 2001::/64 eui-64". Regardless of what IPv6 address is used, the "eui-64" command flips the 7th bit of the address.

What are Optics?

Hot swappable devices that can be easily changed to match requirements or in the event of a failure.

When setting up the TCP 3-way handshake, what is the Window size?

How much information can be sent before an ACK is received.

Give an example of flipping the 7th bit of an IPv6 address after it is converted by EUI-64.

If the first 2 numbers are 1 and 2, the binary equivalent is 0001 and 0010. Flip the 1 in the 7th position to a zero, and that 2 will become a 0, thus changing the hexidecimal number from 12 to 10.

How does the TCP/IP model Application layer compare to the OSI model Application layer?

In the OSI model, the top 3 layers are the Session, Presentation, and Application layers. In the TCP/IP model, all 3 of those layers are combined into the Application layer.

What do you do after erasing the startup-config on a Cisco device?

Issue the "reload" command on the CLI to restart the device.

Does Gigabit Passive Optical Networking, or GPON, use Ethernet standards?

It does use Ethernet frames, but not in the traditional sense. That fact is hidden from the end user.

What is an Auto Medium Dependent Interface Crossover, or MDI-X, interface?

It is an interface that will detect if a crossover cable is required and then adjust as needed.

What are the 2 most common connectors used in modern fiber optic connections.

LC or SC, with the smaller LC connectors being used more frequently.

Name 4 ways that a point-to-point (PTP) WAN connection can be delivered from a provider.

Layer 2, Layer 3, PSTN lines such as T1 and DS3 (not standard Ethernet), and wireless connectivity.

What is at Layer 3 of the TCP/IP model, the Network layer?

Logical addressing, such as IPv4 and IPv6 addresses that are globally unique and sent through routers to reach their destinations.

Even with the popularity of cloud resources, what are 2 advantages to using On-Premises, or On-Prem, resources?

Lower bandwidth over the WAN connection, and lower latency.

What is at Layer 2 of the TCP/IP model, the Data Link layer?

MAC addresses with data structured into frames. The frames include the source and destination MAC addresses in the header.

What does the command "logging synchronous" do?

Makes it so that system messages from the IOS won't interrupt the CLI when you are typing commands. You have to turn it on for every type of interface that will be used to access that device.

What are the 2 primary differences between orange, multimode fiber optic cables and yellow, single mode cables?

Multimode fiber optics are used for shorter distances and are generally cheaper. Single mode fiber optics are used for longer distances, and are usually more expensive.

When creating an enable password on a Cisco device, is that password universal for the entire device?

No, each connection needs to have its own enable password, such as a console connection, an SSH connection, etc. The passwords must be set for every method of accessing that device.

Are Cisco device interfaces enabled by default?

No, so you should always use the "no shutdown" command on any interface that you want to be active.

Does the question mark on the CLI need to be used by itself?

No, you can start to type a command and then use the question mark to see what other commands or options can be used with whatever command or partial word that you have typed so far.

What is at Layer 1 of the TCP/IP model, the Physical layer?

Physical cables and connectors, and anything related to light or electricity traveling over cables.

What ports are used by HTTP and TFTP?

Port 80 and UDP port 69, respectively.

How do you advance through help options that are given when using the question mark on the CLI?

Pressing the Enter key advances one line at a time, while pressing the spacebar advances an entire page at a time.

Name 3 reasons to use a Next Generation Firewall.

Prevent breaches, Identify compromised machines, and Receive alerts.

Name 4 things that are defined by Ethernet standards.

Protocols, Interfaces, Cabling types, and Connectors.

What are 2 options for Cisco devices that will provide centralized authentication services?

RADIUS and Terminal Access Controller Access, or TACACS+.

How are small wireless networks managed vs. large wireless networks?

Small networks can be individually configured and monitored. Large wireless networks will include 10's or 100's of AP's, a Wireless LAN Controller, or WLC, and the network is centrally managed and monitored.

What does the command "no IP domain-lookup" do?

Stops the IOS from trying to find a domain name that was typed into the command line if it was typed incorrectly. It basically disables DNS name resolution so you don't have to wait for the CLI to error out.

How do you figure out how many hosts are available with any given subnet mask?

Subtract the last octet from 256. For example, in a /27 subnet, the last octet of the subnet mask is 224. 256 minus 224 equals 32. That means that the network address would be 0, 32, 64, 96, 128, etc. In each case, the network address is unavailable and the final address is the broadcast address, so each of these subnets would have 30 hosts.

When looking at the name of Ethernet standards, such as 1000Base-T or 1000Base-LX, what do the T and the L stand for?

T is usually going to be a copper LAN cable while an L will normally be fiber optics.

What is the purpose behind setting the "login" command for a console connection to a Cisco device?

The "login" command is a required configuration command to enable password checking at login. Console authentication requires both the password and the login commands to work.

What are a LAN private IP address and a WAN public IP address known as after NAT?

The LAN private IP address is the Inside Local address and the WAN public address is the Inside Global address.

When using a Layer 2/Layer 3 switch, what determines if any given switchport acts as Layer 2 or Layer 3?

The command "switchport" enables switching, which makes it a Layer 2 interface. The command "no switchport" disables switching, making it a Layer 3 interface.

What is NAT overload, also known as Port Address Translation?

The commonly used type of NAT where many private IP addresses are mapped to one, publically routable IP address. Port numbers are used to distinguish traffic flows through the router.

What happens if too much information is sent before an ACK is received during the TCP 3-way handshake?

The data is presumed to be lost and is then retransmitted.

When using NAT overload, or Port Address Translation, how does the router know where to send traffic that is returned to the network?

The port number and IP address for the hosts inside the network are kept in the router's NAT translation table.

Describe a Tier 2 network design.

There are 2 layers of switches. Access switches that aggregate user machines are close to the network endpoints. Access switches are in turn connected to Distribution switches that aggregate the Access switch traffic.

Describe a Tier 3 network design.

There are 3 layers of switches. Access switches that aggregate user machines are close to the network endpoints. Access switches are in turn connected to Distribution switches that aggregate the Access switch traffic. Distribution switches are in turn connected to Core switches that aggregate the Distribution switch traffic.

What is the number and name of the layers of the modern TCP/IP model?

There are 5 layers - Physical, Data Link, Network, Transport, and Application.

What does the CLI prompt look like in enable mode?

There is a hashtag, such as #. It is also known as privileged, or privileged exec mode.

How many collision domains are there when using hubs?

There is one collision domain since hubs rebroadcast all signals they receive out of every single port except the port the signal was received on.

What is the preferred behavior for a switchport if the auto-negotiation process fails?

They should fall back to half-duplex.

When do commands entered from the Cisco CLI take effect?

They take effect immediately, but they are not automatically saved to startup configuration for that device.

What type of transmissions prefer UDP over TCP?

Transmissions such as VoIP and video streaming where speed is more important than every single packet being received.

Do wireless access points, or AP's, perform routing functions?

True AP's that are just AP's will not. However, many SOHO routers are an AP combined with a switch, a router, and various other capabilities.

Why are UDP transmissions faster than TCP transmissions?

UDP does not use acknowledgments, ordering, or duplication protection.

How do you assign an IPv6 address to a Cisco interface?

Use the command "ipv6 address" prior to inputting the IPv6 address, such as "ipv6 address 2001::2/64". Then perform the "no shut" command on the interface.

How can you take a switchport out of full-duplex?

Use the command "no duplex full" on that interface to set it to auto instead of full so it will negotiate with whatever port it is connected to.

How can you view information about a specific port on a Cisco device?

Use the command "show interface fa0/24" to see the details about port 24.

In order to connect separate LAN's to each other, what do routers connect to?

WAN, or Wide Area Networks, such as the Internet, leased lines, etc.

Describe Static NAT, also known as One-to-One NAT.

When a specific host inside a network has their private, internal IP address changed inside the router to another specific, globally routable IP address.

In one command, how can you exit all the way out to a basic privileged exec prompt on the Cisco CLI?

With the "end" command.

How do you save the presently running configuration to the startup configuration for a Cisco device?

With the command "copy run start", and then press Enter when given the option for the destination filename. You can also use the "wr mem" or "write memory" command, which is the older method.

How can you erase a Cisco device startup-config?

With the command "erase startup-config" or "wr erase".

How can you view a quick overview of all interfaces on a Cisco device?

With the command "show ip interface brief".

How do you view the startup configuation for a Cisco device from the command line?

With the command "show startup-config" or "show start".

From enable mode, or privileged exec mode, how do you get to the next permission level using the Cisco CLI?

With the configure terminal, or conf t, command.

How do you get from user exec mode to the next higher permission level to configure a Cisco device?

With the enable command.

Is it possible for VLAN's on a switch to have assigned IP addresses?

Yes, which allows routing between VLAN's. It is done via a Switched Virtual Interface, or SVI, which is a logical VLAN interface.

Can you use the arrow keys on the Cisco CLI?

Yes. The left and right arrows move the cursor forward and backward on the line. The up and down arrows scroll through recently used commands.

How can looking at the details of an interface help with troubleshooting?

You can look for things like the number of input errors to see if there is an on-going problem with that interface.