Glossary of Cisco CCNA Routing Fundamentals

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What 3 things are loaded when the router is initialized?
1. Bootstrap
2. The Operating System
3. Configuration File
What does a router do if it cannot find a configuration file?
Enters setup mode
Where is the backup copy of the new configuration from setup mode stored?
What is the test called that the router performs when it powers up?
After verifying Hardware functions what does the router do next?
Software initialization
Where is the bootstrap program loaded
What is the definition of Bootstrap
A bootstrap is a simple preset operation to load instructions that in turn cause other instructions to be loaded into memory, or cause entry into other configuration modes
Where are three places where the Cisco IOS can be found?
1. Flash
2. TFTP Server
3. ROM
Where is the configuration file saved?
What 3 things does the POST Diagnostics from ROM verify.
1. Basic CPU operation
2. Memory
3. Network Interface ports
How are configuration files loaded into main memory?
one line at a time
what do configuration commands do?
1. Start routing
2. Supply addresses for interfaces
3. set media charachteristics and so on
If no valid configuration file exists in NVRAM, the OS executes a question driven configuration routine. What is this called
System configuration Dialog or setup Dialog
What command shows the backup config files
Show startup-config
What command shows the active config files
Show running-config
What command deletes the backup configuration file in NVRAM
Erase startup-config
What is the reboot command
What is the command used to enter setup mode from the privledged exec prompt
What is the purpose of setup mode?
to bring up, quickly, a minimal configuration for any router that cannot find its configuration from some other source
How do default answers appear in setup mode
in brackets []
what command can be pressed at any time to terminate the process and start over
Control + C
If you want to use the new configuration and you enter yes where will it be saved
What should you do if the MORE promp appears
press space bar to continue
What is the first global parameter you should enter?
Host name
What password is encrypted by Cisco proprietary software?
Enable Secret
How does the enable secret password appear on the config file?
meaningless string of charachters
If you answer yes to the setup configuration what will happen to the configuration file?
it will be executed and saved to NVRAM
if you want to change the setup configuration after you save it what must be done.
You must configure it manually
The script file generated by setup is additive. What does this mean?
You can turn features on with setup but you can not turn them off.
What 3 places can you load configuration files from?
1. Console
3. TFTP server
What five pieces of information does the router use from the configuration files when it starts up?
1. Cisco IOS Software version
2. Router Identification
3. Boot File Locations
4. Protocol Information
5. Interface Configuration
If there is no configuration file in the router, what mode do you enter to configure one?
What command will allow you to configure from a virtual terminal, a modem, or a console terminal?
privledged EXEC configure
What command configures manually from the console terminal.
configure terminal
What command displays the current configuration in RAM?
Show running-config
What command displays the saved configuration, which is the contents of NVRAM?
show startup-config
What command erases the contents of NVRAM?
erase startup-config
What does the command copy running-config tftp allow you to do?
store a current copy of the configuration on a TFTP server.
In copying a running-config to a host do you need to key the IP address of the host?
Do you need to name a config file copied to a TFTP server?
What mode do you need to be in, in order to manage the contents of NVRAM
What command erases the contents of NVRAM
erase startup-config
Where is the runnning config stored?
Where is the startup or backup configuration file stored?
What command stores the current configuration into NVRAM?
copy running-config startup-config
What command displays the saved configuration?
show startup-config
If the screen prompt shows
Router(config-if)# what are you configuring?
the interface
If the screen prompt shows Router(config-subif)# what are you configuring?
the subinterface
What mode are you in when you apply commands that affect the system as a whole?
Global configuration
What do you type to enter global configuration mode from the terminal
Configure Terminal or
Config T
What command do you key to configure a routing protocol?
Router "protocol" for example to configure RIP you type
Router RIP
What mode are all router interfaces automatically in?
administratively down mode
What is the clocking signal on a serial link?
What tyoe of devices are, by default, cisco routers?
what command sets the clockrate?
What command establishes a password on the console terminal?
line console 0
line con 0
What command establishes password protection on incoming telnet sessions?
line vty 0 4
What command uses Cisco proprietary encryption process to alter the password character string?
enable secret password
If you do not configure a router name, what is the default name?
What mode must you be in to change the routers name?
Global Config
What does the command banner motd allow you to do?
Configure a message-of-the-day banner to be displayed on all connected terminals at login
What delivery method does IP use?
Best Effort
What are three reasons data may fail to reach its destination?
1. Hardware Failure
2. Improper configuration
3. Incorrect routing info
What does IP use to notify the sender that the message couldnt be delivered?
What type of message provides information or configuration parameters to hosts?
Control messages
What component of TCP/IP notifies the sender that a data transmission has failed?
What is the acronym for Internet Control Message Protocol?
Does a router know the exact path a datagram took to get to the router?
What is the ONLY information a router has about a datagram?
Only the source and destination IP address of the datagram
Does ICMP correct network problems?
Does ICMP notify the intended receiver that there was a problem delivering the packet?
Why dont error created by ICMP messages generate their own ICMP message?
error reports could generate more error reports, causing increased congestion on an already ailing network
What 3 addresses are needed in TCP/IP configuration if datagrams are to travel outside the local network
1. IP Address
2. Subnet mask
3. Default gateway
What two things must a router have in order to send datagrams?
1. TCP/IP properly configured on it's interfaces
2. An appropriate routing protocol
What is the term that is used when a destination network is not accessable?
Unreachable network
What happens if the destination device recieves the ICMP echo request?
It formulates an echo reply message to send back to the source of the echo request
What command initiates an echo request?
If an echo request is succesful between the source and destination what does that mean.
This confirms ip connectivity betweeen the two devices
What would be created if two routers continually route a datagram back and forth?
Loop - travels in circles
What is the maximum hop count for RIP?
What does TTL stand for?
Time to Live
What 3 fields are common to all ICMP messages?
1. Type
2. Code
3. Checksum
What are four reasons datagrams might not make it to their destination?
1. Hardware failures
2. Improper protocol configuration
3. down interfaces
4. Incorrect routing information
If a "3" appears in the type field what does that mean?
Destination Unreachable
What does the "code value" indicate?
The reason a packet could not be delivered
What is usually needed to forward a datagram from a token-ring to an ethernet network?
Packet fragmentation
If a datagram header has an error what will a device like a router do?
It sends an ICMP type 12 parameter problem message to the source
When the code value of teh problem message reaches 0, what will the pointer field indicate?
the octet of the datagram that produced the error
Why is a control message sent?
To inform hosts of conditions such as network congestion or a better gateway.
How are ICMP control messages sent?
Inside IP datagrams
What is another term for "gateway"
What is the only device that can initiate a Redirect/Change request message?
How is a redirect/change configured on a Cisco router?
It's the default
What allows a host to ask for the current time according to the remote host?
The ICMP timestamp message request
What are the 2 type fields on an ICMP time stamp message?
13 (Timestamp request) or
14 (Timestamp reply)
The code field value is always set to 0, because there are no additional parameters available.
What 3 things are contained in the ICMP timestamp reply message
1. the originate timestamp
2. the receive timestamp
3. transmit timestamp
What 2 things affect true transit time?
1. Traffic
2. Congestion on the network
What 2 protocls are now used to allow a host to find its network number?
What type of message is sent out when a host doesnt know the network address?
Address mask request
What is the mulicast address for router discovery?
What happens if a router receives a multicast request but isnt configured for multicasting?
It doesnt answer the request
If the default gateway is missing, what message is genereated by the host?
router solicitation
What happens when there is too much congestion on a network?
Packets are dropped
Why dont Cisco routers send source quench messages(by default)?
because the source-quench message may itself add to the network congestion
What type of offices might use source quench messages
small office home office
What is the standard for internetwork communications?
What is the transport protocol for the internet?
What is the function of the TCP/IP protocol suite?
Responsible for the reliable transport and regulation of data flow from source to destination
Prior to data transmission, the 2 communicating hosts go through a synchronization process to establish a virtual connection for each session between hosts. This process is called what?
Three way hand shake
Describe the process of a three way hand shake?
1. The source host sends the destination host a request for communication. This is done by sending a sequence number
2. The destination host sends back and Acknowledgement of the sequence number and then adds a 1 to it and sends it back.
3. The source host acknowledges the sequences number+1 that the destination host sent and begins transmitting
DoS stands for?
Denial of Service attack
Describe SYN flooding?
SYN flooding exploits the normal three way handshake and causes targeted devices to acknowledge to source addresses that will not complete the handshake
Describe DoS attack?
the hacker initiates a SYN but spoofs the source IP address. Spoofing is a term used when the receiving device replies to a non-existant, unreachable ip address and then is placed in a wait state until it recieves the final acknowledgement from the initiator
What are some defense mesures for SYN flooding and DoS attacks?
system administrators may decrease the connection timeout period and increase the connection queue size. Software also exists that can detect these type of attacks and initiate defensive measures
Describe how windows provides flow control?
data must be broken into smaller pieces to allow for proper data transmission
What is the purpose of TCP applying sequence numbers to segments?
so that the recieving node can reassemble bytes in the correct order
What does TCP do if a sequence number is missing in a series?
That segment is retransmitted
TCP uses positive acknowledgement and retransmission (PAR) for what?
to control data flow and confirm data delivery
Name the field responsible for trancking of transmitted and received bytes?
the Acknowledgment Number field
What two protocols does the Transport layer provide?
1. TCP
2. UDP
What layer 3 protocol is connectionless?
Which protocol is a connection oriented reliable protocol?
What protocol is connectionless and unreliable?
What advantage does UDP provide over TCP?
TCP provides services for what applications?
1. FTP
4. DNS
UDP is the transport layer protocol used by what applications?
1. DNS
UDP is unreliable - so what layer provides error detection?
UDP does not use windowing or ACK's so APPLICATION LAYER protocols must provide error detection
What are port numbers used to keep track of?
the different conversations that cross the network at the same time
Both TCP and UDP use _________ to pass information to upper layers?
port or socket numbers
What port is used for FTP application?
What port numbers are used for public applications?
Below 255
What is port number 53 used for?
What is the port used for telnet?
The IP address gets the packet to the _______?

The TCP or UDP port number guarantees that the packet is passed to the correct ___________?
correct server

Port numbers in the range of 0 - 1023 used to select proper applications are considered public port numbers and are controlled by ___________?
Internet Assigned Numbers Authority (IANA)
IP addresses gets the packet to the correct server but ___________ GUARANTEES the packet is passed to the correct application?
Be able to determine the difference between TCP segments and UDP segments What information do UDP segments not contain?
No sequence numbers or Acknowledgement fields
List the 3 categories of port numbers.
1. Well known ports
2. Registered ports
3. dynamic or private ports
_______________ are located at he transport layer and are serviced by the network layer?
Port numbers
The Network layer assigns the logical address or ____________, and is then serviced by the Data Link layer, which assigns the physical address or the ______________.
IP address

MAC Address
What is a sequential list of permit or deny statements that apply to addresses or upper layer protocols?
What are two things a router can do with a packet?
Accept or Deny
How are ACL's defined?
On a per-protocol, per direction (in or out), or per port basis
What happens to packets if an ACL is not configured on a router?
all packets passing through the router will be allowed on all parts of the network.
Where are packets either accepted or rejected due to an ACL?
at the interface
How does a router read an ACL?
From top to bottom
What happens to the ACL statements once a match is found in the list?
the accept or reject action is performed and no other ACL statements are checked
What happens if additional condition statements are needed in an access list.
The entire ACL must be deleted and recreated with new condition statements.
What is placed at the end of EVERY ACL?
Implicit Deny Any statement
What mode must you be in to create an ACL?
Global Config
What are the 2 steps in creating an ACL
1. Create the ACL
2. Apply it to an Interface
What are 2 directions ACL's can be placed?
Where should a standard ACL be placed?
Closest to the destination
Where should an extended ACL be placed
Closest to the source
What happens if no match is found on an ACL list?
The packet is denied
What does a 1 mean in wildcard masking?
What does a 0 mean in wildcard masking?
What IP Address and subnet mask will the word any substitute for?
What command shows ALL the ACLs on a router
show access-lists
What do standard ACL's check?
Source IP address
What is the default wildcard mask?
What 4 things can an Extended ACL check?
1. Source Address
2. Destination Packet Address
3. protocol
4. Port number
What type of echo packet is sent to the sender if the packet is discarded?
destination was unreachable
Can you use the wildcard host or any keywords in the command?
What does the ip access-group command link?
an existing extended ACL to an interface
What version of CISCO IOS allowed for named ACL's?
What mode must you be in to configure a named ACL?
Global Config
Where do you place Extended ACLs?
As close to the source as possible
Where do you place standard ACLs?
As close to the destination as possible
Who does a firewall try to keep out the intranet?
intruders that come from the global internet
Where are most firewalls placed?
between the internal network and an external network, such as the internet
What are routers that are situated on the boundries of a network?
Border routers
What 2 types of ACLs are used on packets traveling through a router?
What are the numbers of the virtual ports on a router
0, 1, 2, 3, 4
Why should identical restrictions be placed on all vty lines?
Its impossible to control which line a user will connect on
What does a router do when it determines that a route is the best path to a destination?
It adds that route to its routing table.
What are the 2 most time consuming jobs of a network administrator?
Network testing and troubleshooting
What type of equipment causes the most difficult network problems?
What is the function of a router?
To determine the best path from a source to a destination
What do routers read to make packet forwarding decisions?
Contents of their IP routing table
What does the command show ip route display?
The contents of their IP routing table
What is a manually configured route called?
Static Route
What is a route that can change automatically as neighboring routes update each other with new information?
Dynamic Route
What is used when the router is unable to match a destination network with an entry in its routing table?
Default route
What command establishes a default route in networks using dynamic routing protocols?
ip route


ip default-network
What layer determines the best path for a packet?
Network Layer (Layer 3)
What device determines the best path and forwards the packet from an incoming interface to an outgoing interface
what address is used to get packets from source to destination?
Layer 3 Address
What address never changes no matter how many hops a packet takes?
Source and Destination IP Address
What address changes at each hop or router?
MAC Address
What metric does rip v1 use?
Hop Count
What metric is better higher or lower
What layer should you start with when testing network problems?
Layer 1
What is the most common problem on IP networks?
Errors in the addressing scheme
What is the most important part of troubleshooting?
What layer would a transciever problem be at?
Layer 1
What layer would an improperly configured serial interface be at?
Layer 2
What layer would an incorrect IP address be?
Layer 3
What command is used to test connectivity
What is another name for the "indicator" light on a NIC card that indicates a valid connection
Link Light
What should you do if the interface has indicator lights that do not show a valid connection?
Check for faulty or incorrect cabling
What 3 things are displayed when a ping packet finds a specified system and returns?
Minimum, Maximum, and Average time it takes for a packet to find a specified system and return
What will the command show ip protocol show?
Shows the current state of the active routing protocols
What does IGRP use to balance the load on multiple links?
What does 5 exclamation points indicate when performing a ping?
A successful connection
What command would you use to perform more extensive ping tests?
Extended Ping
Which ICMP message type notifies the source host that a receiving host or network is not available?
Destination Unreachable
What layer does Telnet test
All Layers
What line from show interfaces output would indicate a layer 2 problem?
The line that says

Interface UP Line protocol DOWN
What would an Increasing number of Carrier transitions counts on a serial link indicate?
Bad Link or defective CSU/DSU
What are messages sent by one network device to inform another network device that the virtual circuit between the two is still active?
Who does CDP allow you to discover information about?
Directly connected Cisco devices
What command is used to discover routes that packets take when traveling to their destination?
What command shows the entries for all known networks and subnetworks, and how that information was learned
show ip route
what commadn would identify a router that is delivering bad router information?
Show IP protocols
What command would allow you to check a cable connection if you were in LA and a router was in New York?
Show controllers
What command will turn off all diagnostic output?
no debug all


undebug all
What command will show what is being examined by a debug command?
show debugging
MAC Addresses are how many bits in Length?
Describe communicaton between 2 devices on a LAN
The source device encapsulates data in a frame with the MAC address of the destination device and then transmits it. Everyone on the LAN sees it but the devices with non matching addresses otherwise ignore the frame.
What are some functions associated with Frames
1. Identifies which computers are communicating with one another
2. Signals when communication between individual computers begins and when it ends
3. Flags corrupted Frames
Media Access Control Refers to what?
Rules that determine which computer on a shared-medium is allowed to transmit the data
How do you describe CSMA/CD networks?
One node's transmission traverses the entire network and is received and examined by every node.
What are the important Data Link Layer (Layer 2) functions?
Logical Link Control
Media Access Control
What is true of a deterministic MAC protocol?
It allows hosts to "take turns" sending data
Fast Ethernet Supports up to what transfer rate?
100 Mbps
What are the 2 Gigabit over fiber cable specifications?
What is the transmission medium for 1000BASE-SX?
Short-wave laser over multimode fiber
4D-PAM5 encoding method is used in which Gigabit ethernet?
What happens when 1000BASE-T sends and receives data in full-duplex mode on the same conductor?
A permanent collision on the wire
What is the maximum transmission distance supported by 10 Gigabit Ethernet?
40 Kilometers
What are 3 features of microsegmentation?
1. It enables dedicated access
2. It supports multiple conversations at any given time
3. It increases the capacity for each workstation connected to the network
What do LAN switches use to make forwarding decisions?
MAC Addresses
What best describes one function of Layer 3, the network layer, in the OSI model?
It determines the best path for traffic to take through the network.
What function allows routers to evaluate available routes to a destination and to establish the preferred handling of a packet?
Path Determination
How does the network layer forward packets from the source to the destination?
By using A routing table
What 2 parts of a network layer address do routers use to forward traffic through a network?
Network address and destination IP address
What best describes a routed protocol?
Its address provides enough information to allow a packet to be forwarded from host to host.
What best describes a routING protocol?
A protocol that accomplishes routing throgh the implementation of an algorithm
Whats an advantage of distance vector algorithms?
They are computationally simple
What describes Link State algorithms
It recreates the exact topology of the entire network
Why do routing loops occur?
Slow convergence occurs after a modification to the internetwork.
Describe the concept describing EIGRP as a balanced hybrid routing protocol?
Being that EIGRP is a distance vector routing protocol, it determines best paths, but topology changes trigger routing updates
What is a network with only one path to a router called
Stub network
What best describes a default route?
Route used when the destination network is not listed explicitly in the routing table
What kind of entries does a router initally refer to?
Entries about networks or subnets that are directly connected
What are exterior routing protocols used for?
To communicate between autonomous systems.
If you suspect that one of the routers connected to your network is sending bad routing information what command would you use to check?
router> show ip protocol
Why would you display the routing table?
To identify destination network addresses and next-hop pairs

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