220 results

R In a routing table, 'R' indicates a network that was learned dynamically using RIP.            

R Programming language. First released in 1994  Website  Wikipedia       

R-Drive Image Drive imaging and backup program from R-Tools Technology Inc.   Website  Wikipedia       

rabbit virus (fork bomb)   Wikipedia         

RACE Integrity Primitives Evaluation Message Digest (RIPEMD) (128, 160, 256, and 320-bit digests) Open standard family of cryptographic hash functions. Based on MD4 and is similar in performance to SHA-1. Not very common. Developed in Leuven, Belgium, by Hans Dobbertin, Antoon Bosselaers and Bart Preneel at the COSIC research group at the Katholieke Universiteit Leuven, and first published in 1996.  Wikipedia         

Radeon HD 7970  Released January 9, 2012.  Wikipedia         

Radeon R9 290X  Released Oct 24, 2013.  Wikipedia         

Radeon R9 295X2  Released Apr 8, 2014.  Wikipedia         

Radeon R9 390X  Released June 18, 2015.  Wikipedia         

Radeon R9 Fury  Released July 14, 2015.  Wikipedia         

Radeon R9 Fury X  Released June 24, 2015.  Wikipeddia         

Radeon R9 Nano  Released August 27, 2015.  Wikipedia         

Radeon RX 460 GPU from AMD. Released August 8, 2016.    Wikipedia       

Radeon RX 470 GPU from AMD. Released August 4, 2016.    Wikipedia       

Radeon RX 480 GPU from AMD. Announced May 31, 2016. Released June 29, 2016.  Website  Anand Tech       

Radia Perlman STP is based on an algorithm she invented. Born January 1, 1951.  Wikipedia         

Radio Corporation of America (RCA)    Wikipedia         

RADIUS client Gateway separating what is needed to be authenticated and those trying to authenticate.   Wikipedia         

RADIUS router configurations.

Router(config)# aaa new-model
Router(config)# aaa authentication login default group radius none
Router(config)# radius-server host auth-port 1812 access-port 1813 key WinRadius
Router(config)# username RadUser password RadUserPass
   YouTube  YouTube       

RADIUS supplicant Person or device trying to be authenticated.   Wikipedia         

RAID 0    Website  Wikipedia       

RAID 1 An exact copy (or mirror) of two or more drives. For optimal performance, the drives should be identical in model and capacity.   Wikipedia         

RAID 10    Website  Wikipedia       

RAID 5    Website  Wikipedia       

RAID 6    Website  Wikipedia       

Rail fence cipher Words are spelled out as if they were a rail fence.   Wikipedia  Netacad       

Raja Koduri Senior Vice President and Chief Architect, Radeon Technologies Group.   AMD Executive Biography         

Ralph Merkle    Wikipedia         

rand =rand(x,y) Adds random text to a word document.            

Random Early Detection (RED) (aka: random early discard, random early drop) QoS tool that seeks to avoid congestion before it becomes an issue on the network.   Wikipedia         

Random-Access Memory (RAM) Volatile. In networking devices, RAM is used to store the running IOS, running configuration file, IP routing and ARP tables, and packet buffer.   Wikipedia         

ransomware Type of malware that requests payment to remove itself.   Wikipedia         

Rapid Application Development (RAD)             

Rapid PVST+ The Cisco implementation of RSTP on a per-VLAN basis.     Netacad       

Rapid Spanning Tree Protocol (RSTP) IEEE 802.1w evolution of the original STP 802.1D standard.   Wikipedia         

Rapid STP (RSTP) (802.1w)     Cisco       

Raspberry Pi    Website         

ratio A comparison of two numbers.

x to y
x/y(x over y)

raw_input() Wait for 'Enter' to be pressed before terminating in Python.   StackOverflow         

Razr Series of phones made by Motorola. First released in 2004.  Wikipedia         

RC Algorithms

RC1 Never published.
RC2 Variable key-size block cipher that was designed as a 'drop-in' replacement for DES.
RC4 World's most widely used stream cipher.
 Designed all or in part by Ronald Rivest.  Wikipedia  Netacad       

RCA Cable Red, White (audio) and, Yellow (video) analog cable. A type of coaxial cable.   Wikipedia         

rd Command that removes a directory.            

Read Only Memory (ROM) Non-volatile. In networking devices, ROM is used to store bootstrap instructions, basic diagnostic software, limited IOS.            

Read The F% Manual (RTFM) Acronym telling people to read the manual before asking why something doesn't work. Usually for simple/obvious mistakes that would have been avoided should the person have read the instructions. The F% can represent freaking, flipping, or other expletive to express emotion.            

Read-Host PowerShell cmdlet that prompts a user for input.   TechNet         

read-only (ro) Less overhead.            

Read-Only Domain Controller (RODC)      Wikipedia       

read-write (rw) might open up security holes            

readonly Bash builtin to set a variable to read-only. Example: readonly VARIABLE. Same as declare -r.            

Ready Player One  Released March 30, 2018.  IMDB  Wikipedia       

ReadyBoost Caching feature built into Windows Vista and later. Uses ReadyBoost-capable flash memory for better performance in random disk reads. Requires a drive between 256 MB and 32 GB, 1ms access time, 2.5 MBs 4 KB random read, and 1.75 MBs 512 KB random writes.   Wikipedia         

real number Any number that can be represented on a number line.   Wikipedia  Khan Academy       

Real Time Clock (RTC)             

Real-Time Executive for Multiprocessor Systems (RTEMS) (formerly Real-Time Executive for Missile Systems, Real-Time Executive for Military Systems) Free and open-source Real-Time Operating System (RTOS) designed for embedded systems. Development began in the late 1980s with early versions available via ftp as early as 1993.  Website  Wikipedia       

Real-Time Messaging Protocol (RTMP) (port 1935)   Wikipedia         

Real-time Transport Protocol (RTP or RTTP)    Wikipedia         

Realtek Audio-Video Background process (RAVBg64) RAVBg64.exe   file.net         

Received Signal Strength Indicator (RSSI) Measures the power of a wireless signal.            

reconnaissance attack Gathers information about devices on the network and scans for access. This can include the use of packet sniffers and port scanners.   Netacad  Wikipedia       

record A row of information in a database. An item.   Wikipedia         

RECOVER DOS command that recovers readable information from a bad or defective disk.   Wikipedia         

Recovery Point Objective (RPO) Maximum allowable amount of data (measured in time) an organization can afford to lose in an incident. I.E. the RPO for XYZ Company may be 4 hours.   Wikipedia         

Recursion Repeating items in a self-similar way.   Wikipedia  Wikipedia       

Recursive acronym An acronym that refers to itself or another acronym, sometimes humorously.            

recursive lookup When a router has to do multiple lookups in a routing table to forward a packet. A next-hop IP address used in a static route would cause a recursive lookup. These should be avoided when possible.            

recursive static route A static route that uses an IP address as the next hop rather than an exit interface.   Cisco         

Red Hat Runs RHEL. Headquarters are in Raleigh, North Carolina. Founded in 1993.  Website  Wikipedia       

Red Hat Enterprise Linux (RHEL) A Linux distribution used in servers and workstations because of its performance and support. Essentially the more stable release of Fedora.   Website  Wikipedia       

Red Hat Linux (RHL)    Wikipedia         

redgedit Executable that can edit the registry in Windows.   Microsoft Support         

Redircmp.exe Redirects the default container for newly created computers to a specified, target organizational unit (OU) so that newly created computer objects are created in the specific target OU instead of in CN=Computers. Example: redircmp ou=newcomputerou,dc=domainname,dc=com   TechNet         

redistribute When two networks running different routing protocols need to communicate their route can be redistributed. Static routes ( quad zero) can be used for connecting to ISPs.      Cisco       

Reduced Instruction Set Computing (RISC) Type of microprocessor that uses a simplified instruction set for better performance. Originated in the 1960's.  Wikipedia         

Redundant Array of Independent Disks (RAID) (formerly: Redundant Array of Inexpensive Disks) Configuration of multiple disks for redundancy (mirroring/parity) and sometimes performance (striping with RAID 0). Term "RAID" was invented by David Patterson, Garth A. Gibson, and Randy Katz at the University of California, Berkeley in 1987.  Wikipedia         

refactoring Process of restructuring existing computer code (changing the factoring) without changing its external behavior. A refactored file will work correctly but might also perform other malicious actions. Man in the Middle (MITM) might be the result of the refactor, but is not the threat itself.   Wikipedia         

reference model For networking, it clarifies the processes of networking and makes troubleshooting easier. Examples include TCP/IP and OSI.            

referential integrity Ensures the primary and foreign keys match.   Wikipedia         

Reflexive ACL Allow packets to be filtered based on upper-layer session information.   Csico         

refresh rate (aka: "vertical refresh rate", "vertical scan rate" for cathode ray tubes) Number of times in a second the image on the screen can be completely redrawn by updating its buffer.   Wikipedia         

Regional Internet Registries (RIRs) RIRs are responsible for allocating IP addresses to ISPs.            

register High-speed memory in a processor.   Wikipedia         

Registered Dual In-line Memory Module (RDIMM) (aka: buffered memory) Includes a specialized register chip that acts as a buffer between the DRAM modules and the memory controller. By buffering these signals, the electrical load placed on the controller is reduced because the memory controller communicates in series with the register, instead of in parallel with the memory chips.   Wikipedia         

Registered Jack (RJ) (ISO 8877) Standard connector used in data and telecommunication networks.   Wikipedia         

Registered Ports 1024-49151            

registry Similar to the Linux kernel.   Wikipedia         

regular expression Matches a pattern or sequence of characters.   Wikipedia         

rel HTML tag attribute. Specifies the relationship between the current document and the linked document.   W3Schools         

Relational Database Management System (RDBMS) Type of database management system (DBMS) based on the relational model of data. Most databases in widespread use today are based on this model.   Wikipedia         

Relative Distinguished Name (RDN)    Wikipedia  YouTube (Microsoft MCSA/MCSE Learning Channel)       

Relative ID (RID)             

Reliable Transport Protocol (RTP) Used in EIGRP. (TCP)   Wikipedia         

REM Command that records comments (remarks) in batch files or CONFIG.SYS.            

Remington Rand Originally a typewriter manufacturer and later the manufacturer of UNIVAC. 1927  Wikipedia         

Remote Access Trojan (RAT) Malicious software that is typically unknowingly installed which opens a back door for hackers. Notable examples include: Back Orifice, NetBus, iControl, PoisonIvy, Sub Seven, Beast Trojan, Bifrost, Blackshades, and DarkComet.   Wikipedia         

Remote Administrative Access Character mode     Netacad       

Remote Authentication Dial-In User Service (RADIUS) (UDP ports 1812, 1813,1645) Form of AAA used for authentication and network access. Does not handle authorization like TACACS+. Can use usernames and passwords from a variety of locations including on another server.   Wikipedia         

Remote Desktop Protocol (RDP) (TCP port 3389 UDP port 3389) Proprietary Microsoft protocol.   Wikipedia         

Remote Desktop Services (RDS)    Wikipedia         

remote host Located on a remote network and have different network addresses.            

Remote Installation Services (RIS)    TechNet  Wikipedia       

remote network Network that originate from another router and have different network addresses.            

Remote Network Network/packet mode   Microsoft TechNet  Netacad       

remote network entries

{ Router source | Destination network | [Administrative distance/Metric] | Next-hop | Route timestamp | Outgoing interface }


Remote Office / Branch Office (ROBO)             

Remote Procedure Call (RPC)             

remote route Entry in a routing table that came from a remote network. Can be configured manually or learned dynamically.            

Remote Server Administration Tools (RSAT)             

remote-access VPN Connects individual users to a corporate network. Dynamic   Wikipedia         

ren Bash Command that renames a file or files in.   Wikipedia         

rename DOS command that renames a file or files.   Wikipedia         

Rename-Computer PowerShell command to change the hostname after restart.

Rename-Computer -NewName DC1 -Restart

Rename-Item (aka: ren, rni) PowerShell cmdlet used to rename files and folders.   TechNet  Wikipedia       

repetition control structure (aka: iteration control structure) Series of statements in a loop.            

replace DOS command that replaces files.            

replay attack Reusing intercepted non-secure credentials to gain access to a system or network.            

reported distance metric            

REpresentational State Transfer (REST) Lightweight and scalable software architectural style that defines a set of constraints to be used for creating Web services. Web services that conform to the REST architectural style, called RESTful Web services, provide interoperability between computer systems on the Internet. RESTful Web services allow the requesting systems to access and manipulate textual representations of Web resources by using a uniform and predefined set of stateless operations. Other kinds of Web services, such as SOAP Web services, expose their own arbitrary sets of operations.   Wikipedia         

residual risk What risk remains after all mitigation and reduction strategies have been implemented.            

Resilient File System (ReFS)  Released with Windows Server 2012 August 1, 2012.  Wikipedia         

Resilio Sync (formerly BitTorrent Sync) Proprietary peer-to-peer file synchronization tool. Anounced January 24, 2013. Renamed to Resilio Sync on June 1, 2016 when it became managed under Resilio Inc.   Website  Wikipedia       

reverse proxy Hides the server and can provide load balancing and caching for high activity pages.   Wikipedia         

Revo Uninstaller    Website  Wikipedia       

RG-59 Type of coaxial cable, often used for low-power video and RF signal connections. The cable has a characteristic impedance of 75 ohms, and a capacitance of around 20pF/ft (60pF/m). Center conductor of 0.762mm. Sufficient for analog cable TV but not digital. Has a maximum distance of about 228 meters (750 feet).   Wikipedia         

RG-6/U Type of coaxial cable commonly used for cable TV or internet. Has a characteristic impedance of 75 ohms. Center conductor of 18 AWG (1.024 mm), can run up to 304 meters, or 1000 feet. Supports digital signals.   Wikipedia         

RG-8 Type of coaxial cable that was commonly used with 10Base5 (thicknet).   Wikipedia         

risk acceptance Risk response where the likelihood and the impact are less than the cost of mitigation. Level of risk the management authority chooses to accept with or without mitigations in place.            

Rivest Cipher 4 (RC4) (aka: Alleged RC4 (ARC4), ARCFOUR) (1 round, 40-2048 bit key) Stream cipher popularized by its speed and simplicity. Part of some commonly used encryption protocols and standards, such as WEP, WPA, SSL, and TLS. Designed by Ron Rivest in 1987. Initially a trade secret, but in September 1994 a description of it was anonymously posted to the Cypherpunks mailing list. Prohibited for all versions of TLS by RFC 7465 in 2015, due to the RC4 attacks weakening or breaking RC4 used in SSL/TLS.  Wikipedia         

Routed Mode Firewall mode on the Cisco ASA. Functions as a Layer 3 device.    Netacad         

Request for Comments (RFC) Information about protocols and concepts that run the internet.   Website         

Research Triangle Park (RTP) One of the world's largest research parks. Located in North Carolina. Founded in 1959.  Wikipedia         

Reseaux IP Europeans (RIPE NCC)    Website         

reset (RST) TCP flag.            

resistance (R)    Wikipedia         

resistor Resists the flow of electricity.     YouTube (Make:)       

Resource Records (RR)             

Resource Reservation Protocol (RSVP) QoS IntServ mechanism that reserves resources for an integrated services internet.  Operates at OSI Layer 4 (transport). Defined in RFC 2205 September 1997.  Wikipedia  RFC 2205       

Responsive design Same concept as RWD just generalized for other applications.   Wikipedia         

Responsive Web Design (RWD) Web pages that scale and resize depending on the size of the screen or browser window.   Wikipedia         

Restart-Computer PowerShell command that restarts Windows.            

Restart-NetAdapter PowerShell command to restart a network adapter by disabling and then re-enabling the network adapter.

PS C:\> Restart-NetAdapter -Name "Ethernet 2"


Restart-Service PowerShell command to restart services.

Restart-Service -Name Spooler -ForceRestart the print spooler.

Resultant Set of Policy (RSoP) Command rsop   TechNet         

Reverse Address Resolution Protocol (RARP) Ethernet type 0x8035.            

Rich Site Summary (RSS)    Wikipedia         

Rich Skrenta Wrote the Elk Cloner virus.   Wikipedia         

Richard Stallman    Wikipedia         

Rijndael block cipher Developed by Joan Daemen and Vincent Rijmen.            

RingCentral Cloud-based phone system. Founded in 1999   Website  Wikipedia       

Riser Cabling (Also known as Vertical cabling)    Wikipedia         

risk assessment (aka: risk identification) Evaluating probability and impact. Consists of a vulnerability assessment and a threat assessment. Threats + Vulnerability = Risk.   Wikipedia         

risk avoidance Risk response where the likelihood and the impact are so high that it is not dealt with. (i.e. not collecting PII because if it leaked, you could no longer do business.)            

risk management framework


risk mitigation Risk response that reduces risk to a lower level.            

risk response Process of how to handle risks. The four parts are:


risk transference Type of risk response where some of the risk, likelihood, and impact is offloaded to a third-party. (i.e. cloud hosting.)            

Rivest-Shamir-Adleman (RSA) One of the most common asymmetric algorithms in public key cryptography. Typically used to generate digital signatures. Keys are usually 512 to 2048 bits. Acronym is the first letter from each surname of the developers; Ron Rivest, Adi Shamir, and Len Adleman. Published in 1977.  Wikipedia         

Rivest-Shamir-Adleman keys (RSA keys)    Wikipedia  Cisco Learning Network       

Rivest-Shamir-Adleman signatures (RSA signatures) Authentication method used by IPsec   Wikipedia         

RJ-45 plug The standard connector used for LANs on Ethernet cable.            

rm UNIX command to delete. Use del in DOS or OS/2.   Wikipedia         

rmdir DOS command that removes a directory.            

Robert Kahn One of the fathers of the internet.   Wikipedia         

Robert Metacalf Founded 3COM.   Wikipedia         

Robert Noyce  Co-founded Fairchild Semiconductor in 1957 and Intel Corporation in 1968. December 12, 1927 - June 3, 1990  Wikipedia         

Robust File Copy for Windows (ROBOCOPY)    Wikipedia  Microsoft TechNet       

Robust Security Network (RSN) Type of authentication.   Windows Hardware Dev Center         

Robust Security Network Association (RSNA) Type of authentication.   Windows Hardware Dev Center         

Robust security Network Association with Preshared Keys (RSNA-PSK) Type of authentication.   Windows Hardware Dev Center         

Rogue Access Point (Rogue AP) A wireless access point that has been installed on a network without explicit authorization from an administrator, whether added by a well-meaning employee or by a malicious attacker. Could be used by unauthorized individuals to bypass security controls such as firewalls. The potential of bypassing security controls is a good reason to perform a site survey of rogue access points.   Wikipedia         

Rogue One: A Star Wars Story  Released December 16, 2016.  IMDB         

Rollover Cable (Console Cable) T658A to reversed T658A.   Wikipedia         

Ron Rivest             

Ronald Wayne Co-founded Apple Computer with Steve Wozniak and Steve Jobs. Born May 17, 1934.  Wikipedia         

root user            

root (/)             

root bridge Bridge with the smallest (lowest) bridge ID. Switch in STP that determines which redundant paths to block. The root bridge switch can be set with a priority of 0. If multiple devices have a priority of 0, it will chose the one with the lowest MAC address.   Wikipedia         

root hints Resolve queres for zones that don't exist on the local DNS server. Only use if forwaders are not configured or fail to respond   YouTube (Microsoft MCSA/MCSE Learning Channel)         

root mean square (RMS) (aka: effective value)


root port Switch ports closest to the root bridge            

Roslyn .NET compiler   Wikipedia         

Round Robin (RR) Network scheduling algorithm.   Wikipedia         

route -n Linux command to show the routing table. (Use route print for Windows.)            

route poisoning    Wikipedia         

route print Shows the routing table in Windows. (Use route -n for Linux.)            

route resolvability The process used by the routing table to determine the exit interface used to forward a packet.            

route source How a route was learned in a routing table. Usually represented by the first letter of the routing protocol or the kind of connection. (i.e. R for a RIP route, C for a directly connected route, S for a static route...)            

route summarization (route aggregation) advertising a contiguous set of addresses as a single address with a less-specific, shorter subnet mask.            

route timestamp When a route was last heard in a routing table.            

router routes packets across different networks and to other devices on the current network.   Wikipedia         

Router Discovery Protocol (RDP)             

router eigrp IOS command used to enable EIGRP (no router eigrp turns it off)            

router ID Both IPv4 and IPv6 use the same 32-bit router ID in EIGRP. Can be configured with the            

router on a stick Allows hosts logically separated by a VLAN to communicate.   Wikipedia         

router rip command used on routers to enable RIP            

Router Solicitation (RS) When configured with SLAAC, a host will send an RS message to the router.            

routing Choosing the best path through a network.   Wikipedia         

Routing Header (RH)             

Routing Information Base (RIB) Also known as the routing table.   Wikipedia         

Routing Information Protocol (RIP) (Administrative Distance: 120, UDP port 520) Distance-vector routing protocol that uses hop count as a routing metric. Has a maximum hop count of 15. Implements the split horizon, route poisoning and holddown mechanisms to prevent incorrect routing information from being propagated. Uses multicast address   Wikipedia         

Routing Information Protocol (RIPng) An extension of RIPv2 that supports IPv6.   Wikipedia         

Routing Information Protocol Version 2 (RIPv2) Uses UDP through port 520. Broadcast    Wikipedia         

routing loop Where duplicate frames are sent across the network to the same router and get stuck in a loop.   Wikipedia         

routing protocol How routers communicate with each other. A set of processes, algorithms, and messages used to exchange routing information and populate the routing table with the best path.   Wikipedia         

routing table Each router or computer has a unique routing table of where to send packets. Volatile. Table in the OSPF forwarding database. [Route source | Destination network | Outgoing interface] Can be shown using route print on Windows, route -n on Linux, and show ip route on Cisco IOS.   Wikipedia  Microsoft TechNet       

RS-232 (serial connection) Now replaced by the newer USB standard on PCs. Some WANs may still use a serial connection though.   Wikipedia  Wikipedia       


RS-423    Wikipedia         

RSA Conference 2018  April 16 - April 20.  Website         

RSA Congerence USA 2019  March 4-8, 2019 at Moscone Center in San Francisco.  Website         

RSA signature             

RSA-encrypted nonce    Wikipedia  Cisco Press       

rsync Backup utility for Linux-based computers.   Wikipedia         

RTLinux Hard realtime RTOS microkernel that runs the entire Linux operating system as a fully preemptive process. Discontinued August 2011.  Website  Wikipedia       

RTV-G-4 Bumper United States rocket. Bumper 8 was the first successful rocket to launch from Cape Canaveral on July 24, 1950.  Wikipedia         

ruby programing language.   Wikipedia  Code School - Try Ruby       

ruby on rails Open-source web framework.   Wikipedia  Website       

running configuration file Current configuration in Cisco IOS            

Ryzen (codename: Summit Ridge) CPU family from AMD. Announced February 22, 2017. First relesed March 2, 2017.  Website  Wikipedia