Here are some of the most commonly used abbreviations you should know in CCNA and in common. Just bookmark this page in case you need it again:

*(CSMA/CD) carrier sense multiple access collision detect
*(OUI) organizational unique identifier
*(GBIC) gigabit interface converter
*(DTE) data terminal equipment
*(DCE) data communications equipment
*(NIC) network interface card
*(NOS) network operating system
*(VoIP) voice over IP
*(QoS) quality of service

*(UPS) uninterruptible power supplies
*(DNS) domain name system
*(IDS/IPS) intrusion detection system/intrusion prevention system
*(SSH) secure shell
*(SSL) secure socket layer
*(SNMP) simple network management protocol
*(NTP) network time protocol
*(PDU) protocol data units
*(UDP) user datagram protocol
*(DARPA) defense advanced research projects agency
*(IP) internet protocol
*(NAT) network address translation
*(FTP) file transfer protocol
*(TFTP) trivial file transfer protocol
*(SMTP) simple mail transfer protocol
*(DHCP) dynamic host configuration protocol
*(IANA) internet assigned numbers authority
*(Telnet) terminal emulation
*(SYN) (for synchronize)
*(ISNs) initial sequence numbers
*(ACK) acknowledgment
*(ARP) address resolution protocol
*(MAC)media access control
*(LLC) logical link control
*(SAP) service access points
*(SNAP) subnetwork access protocol
*(RF) radio frequencies
*(IR) infrared
*(ASICs) application-specific integrated circuits
*(VLAN) virtual LANs
*(CRC) cyclic redundancy check
*(CLI) command-line interface
*(POST) power-on self test
*(RPS) redundant power supply
*(STAT) port status
*(UTL) bandwidth utiltzation
*(FDUP) full-duplex
*(MOTD) message of the day
*(VMPS) VLAN membership policy server
*(STP) spanning tree protocol
*(RF) radio frequencies
*(AP) access point
*(CSMA/CA) carrier sense multiple access collision avoidance
*(EIRP) effective isotropic radiated power
*(DSSS) direct sequence spread spectrum
*(OFDM) orthogonal frequency-division multiplexing
*(WEP) wireless equivalency privacy/wireless encryption protocol
*(WPA) wi-fi protected access
*(TKIP) temporal key integrity protocol
*(AES) advanced encryption standard
*(SSID) service set identifier
*(PSK) pre-shared key
*(BSS) badic service set
*(ESS) extended service set
*(CIDR) classless interdomain routing
*(PING) packet inter net groper
*(IEEE) Institute of Electrical and Electronic Engineers
*(SOF) Start of Frame
*(FCS) field or frame checksum sequence
*(BIA) burned-in address
*(EMI) electromagnetic interference
*(CAM) content addressable memory
*(PCS) persunal communications service
*(RTS) ready-to-send
*(CTS) clear-to-send
*(ITU-R) international telecommunication union-radio communication sector
*(MHz) 1 million cycles per second
*(GHz) 1 billion cycles per second
*(ISM) Industrial,Scientific,and Medical
*(UNII) Unlicensed National Information Infrastructure
*(CCK) Complementary Code Keying
*(MIMO) Multiple Input Multiple Output
*(PSK) per-shared keys
*(WEP) wired equivalent privacy
*(CMIC) cisco message integrity check
*(EAP) extensible authentication protocol
*(EAPoL) EAP over LAN
*(RADIUS) Remote Authentication Dial In User Service
*(PPP) point-to-point protocol
*(CHAP) challenge handshake authentication protocol
*(LEAP) Lightweight EAP
*(PEAP) Protected EAP
*(CCMP) CBC-MAC Protocol
*(SOHO) small ofice home ofice
*(IBSS) Independent Basic Service Set
*(BSSID) Basic Service Set Identifier
*(BSA) Basic Service Area
*(ESA) Extended Service Area
*(WZC) wireless zero configuration