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CCNA - Network Fundamentals
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 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 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 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. What is at Layer 4 of the TCP/IP model, the Transport layer? -
- Transmission Control Protocol (TCP). 2) User Datagram Protocol (UDP). 3) Port numbers from 1 to 65,535. What ports are used by HTTP and TFTP? - Port 80 and UDP port 69, respectively. What is at Layer 5 of the TCP/IP model, the Application layer? -
- How software communicates with lower-level protocols, such as how a web browser uses HTTP to pull information from a web server. 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. 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. Name 4 things that are defined by Ethernet standards. - Protocols, Interfaces, Cabling types, and Connectors. 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. 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. 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. Name 5 functions or features of a Next Generation Firewall, or NGFW. -
- Unified Threat Management, or UTM. 2) A standard firewall. 3) Web filtering. 4) Inline file scanning. 5) Intrusion Prevention System, or IPS. Name 3 reasons to use a Next Generation Firewall. - Prevent breaches, Identify compromised machines, and Receive alerts. 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. 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. What are Tier 2 networks sometimes called? - A Collapsed core design, referring to the Distribution layer switches that are the core of the network. 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 a Data center? - A dedicated space designed for computer and telecom equipment. It includes redundant cooling, power, and telecom communications with providers. 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 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 Fiber to the Home, or FTTH? - Fiber Internet connectivity delivered via Gigabit Passive Optical Networking, or GPON. 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.
From configure mode, use the command "hostname RTR1" to name the device RTR1. 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. 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. 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. 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. 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. 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 view the startup configuation for a Cisco device from the command line? - With the command "show startup-config" or "show start". 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. 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". What do you do after erasing the startup-config on a Cisco device? - Issue the "reload" command on the CLI to restart the 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. 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. 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. 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. 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. 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. What are 2 options for Cisco devices that will provide centralized authentication services? - RADIUS and Terminal Access Controller Access, or TACACS+. 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. 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. 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.
How much information can be sent before an ACK is received. 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. 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. Why are UDP transmissions faster than TCP transmissions? - UDP does not use acknowledgments, ordering, or duplication protection. 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. What is the subnet mask for 192.168.1.0/24? - 255.255.255. What is the subnet mask for 192.168.1.0/25? - 255.255.255. What is the subnet mask for 192.168.1.0/26? - 255.255.255. What is the subnet mask for 192.168.1.0/27? - 255.255.255. What is the subnet mask for 192.168.1.0/28? - 255.255.255. What is the subnet mask for 192.168.1.0/29? - 255.255.255. What is the subnet mask for 192.168.1.0/30? - 255.255.255. What is the subnet mask for 192.168.1.0/31? - 255.255.255. 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. 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.
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. 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. 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". 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. 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 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. 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. 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. How do you assign an IPv6 address to a Cisco interface? - Use the command "ipv6 address" prior to inputting the IPv6 address, such as "ipv address 2001::2/64". Then perform the "no shut" command on the interface. 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 are the 3 parts of using the Extended Unique Identifier 64, or EUI-64, to create an IPv address? -
- 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.
It is automatically created on Layer 3 interfaces on any device running IPv6. Link- local addresses only exist on Layer 2 segments and are not routable. They are used as the next-hop address in router tables. What do Link-local addresses always begin with? - FE80::/10, which means that all of the addresses will start with either FE8, FE9, FEA, or FEB. Can you manually configure an interface's Link-local address? - Yes, when you configure the IPv6 address of an interface, append "link-local" to the end of the command. Describe an IPv6 Multicast address. - An IPv6 address that always falls in the FF00::/8 range, and that uses scoping extensively to see how far into a network a multicast will reach. What are the 8 scoping values for multicasting with IPv6? - 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x8, 0xe, and 0xf. What is an IPv6 Solicited-node multicast address? - An address generated by a router that the router must always listen to. How is an IPv6 Solicited-node multicast address calculated? - Start with FF02::1:ff/104 and then add in the last 6 characters of the unicast address. What is an IPv6 Anycast address? - When multiple routers advertise exactly the same IPv6 address at the same time. The purpose is to provide redundancy, to minimize latency because hosts can choose their closest router, and for load balancing. How do you create an Anycast address? - When issuing the command to assign an IPv6 address to an interface, add the word "anycast" to the end of the command. What are 2 IPv6 special addresses, and what do they mean? - 2 colons together, such as ::, represent an unknown host. 2 colons followed by the number 1, such as ::1 represent the Loopback address. What information can be found in the ARP cache? - The presently known table of MAC addresses that match up to IP addresses in that network. When a host sends an ARP request, what information do they already have? - The IP address of the host that they want to communicate with, and they are asking for the MAC address. What does the arp-a command do? - Brings up the ARP table on that device. What is the Nexux 1000 V virtual switch? -
A Cisco product that plugs into virtual infrastructure to allow the power of Cisco switching inside a virtual environment. It allows both switching as well as advanced security. What is the Cisco Unified Computing System, or UCS? - A hardware system made up of virtualization support, switching, compute hardware, and management software. What is the IPv6 equivalent of the type of IPv4 address resulting from RFC 1918 addressing?
- RFC 1918 addressing refers to a unique IPv4 address assigned to a specific host. The IPv6 equivalent of that is the IPv6 unique local address.
