General Flashcards
Use straight thru cables
Switch to router
Computer to switch
Computer to hub
Use crossover cable
Switch to switch Switch to hub Hub to hub Router to router Computer to computer Computer to router
Access layer
Provides local and remote user access
Controls which devices are allowed to communicate on the network
Distribution layer
Controls flow of data between access and core layers
Delineates broadcast domains by performing routing functions between VLANs defined at access layer
Core layer
High speed backbone
Highly available and redundant
Work area
Locations of end devices used by individual
Telecommunications room
Where connections to intermediary devices take place
House hubs, switches, routers, and data service
Horizontal cabling
Cables connecting the telecommunications rooms with the work areas
Backbone cabling
Cabling used to connect the telecommunication rooms with the equipment rooms
Interconnects LANs between buildings
Aggregated traffic
Network diameter
Number of devices a packet has to cross before destination
CPE
Customer premises equipment
DCE
Data-circuit-terminating equipment
Puts data on local loop
DTE
Data terminal equipment
Carrier equipment connects subscriber to the WAN
Local loop
Cable that connects the CPE to the central office
Last mile
Demarcation point
Connects CPE to local loop
CSU/DSU
Channel service unit(CSU) provides termination for digital signal, error correction, and monitoring
Data service unit(DSU) concerts t-carrier line frames into frames the LAN Can read and vice versa
WAN data link protocols
HDLC point-to-point protocol Frame relay ATM MPLS
Network documentation
Should include
- network topology diagram
- network configuration table
- end system configuration table
- network baseline
User exec mode
Access to limited number of basic monitoring and troubleshooting commands, such as show and ping
Privileged exec mode
Full access to all device commands, including configuration and managememt
Up arrow or ctrl-p
Go back thru command history
Up arrow or ctrl-n
Go forward in command history
Typing tab in CLI
Auto completes a partial command entry
Command to enter global configuration mode
Configure terminal
Login command
Requires password to be entered
Enable secret
Creates password and stores it encrypted
service password-encryption command
Encrypts all passwords in configuration file
transport input ssh command
Entered in line configuration mode
Only allows SSH telnet connections
General troubleshooting method
Step 1: analyzing/predicting normal operation
Step 2: problem/solution
Step 3: root cause analysis
Use ping to test connectivity
- can device ping itself
- can device ping default gateway
- can device ping the destination
when DHCP server is on a different LAN
enter ip helper-address command followed by address of server on router interface for separate LANs
DNS A record
an end device address
DNS NS record
an authoritative name server
DNS CNAME record
the canonical name ( or fully qualified domain name) for an alias
DNS MX record
mail exchange record
maps a domain name to a list of mail exchange servers
in IPv6 what is analogous to a subnet mask
prefix
-if prefix length is not on quartet boundary write down value for entire quartet
how to abbreviate IPv6 address
- omit leading 0s in any given quartet
- represent 1 or more consecutive quartets of all hex 0s w/ a double colon (::), but only for one such occurence
show filesystems content
dir command
cisco filesystem URL structure
prefix[//location]/directory]/filename]
boot system command
can be used to specify which ios image to boot from
recover lost cisco password
- turn off router
- press break key
- enter confreg 0x2142
- enter reset
- skip initial config
- copy startup-config running-config
- enter enable secret for new password
- enter config-register 0x2102
- copy run start
- verify config
dynamic NAT
uses a pool of public addresses and assigns them on a first come first serve basis. when a host with a private ip requires access to the internet, dynamic NAT chooses an ip from the pool thats not already in use by another host
static NAT
uses a 1 to 1 mapping of local and global addresses, useful for web servers or hosts that need a consistent internet address
NAT overload
aka port address translation (PAT)
maps multiple private IPs to a single public ip or a few addresses
each private address is tracked by a port #
configure static NAT
ip nat inside source static local-ip global-in
specify interface w/ ip nat inside command
specify outside interface w/ip nat outside
configure dynamic NAT
1)define pool of global address
#ip nat pool *name start-ip end-ip {netmask *netmask*| prefix-length *prefix length*}
2) define standard ACL permitting addresses to be translated
3)bind pool of addresses to ACL
4)specify interfacesconfigure NAT overload
ip nat inside source list ACL# interface interface# overload
NAT show commands
show ip nat translations
show ip nat statistics
reset dynamic nat
clear ip nat translation
troubleshooting NAT
1) based on config, clearly define what NAT is supposed to achieve
2) verify correct translations exist in the translation table using show ip nat translations
3) use clear and debug commands
4) review in detail what is happening to packet
use ping to test connectivity
can device ping itself?
can device ping default gateway?
can device ping the destination?
100BASE-TX
cat 5UTP
100BASE-FX
multimode fiber
1000BASE-SX
single mode fiber
1000BASE-LX
multi mode fiber
terminal settings for pc to device via console port
Speed: 9600 b/s Data bits: 8 Parity: None Stop bit: 1 Flow control: None
command to view open ports on switch/router
show control-plane host open-ports
