O
- O command (sendmail), Setting Options
- octet data, MIME encoding, Multipurpose Internet Mail Extensions
- octet-stream (MIME data subtype), Multipurpose Internet Mail Extensions
- Oerrs field (netstat command), The Interface Name
- official Internet addresses, assessing need
for, Obtaining an official network address–Obtaining an official network address
- ONBOOT (Linux configuration value), Assigning an Address
- one-time passwords, One-Time Passwords, OPIE–OPIE
- OPIE, OPIE–OPIE
- ONEX command (ESMTP), Multipurpose Internet Mail Extensions
- only_from parameter (xinetd), Controlling Access with xinetd
- OPEN messages (BGP), Border Gateway Protocol
- Open Shortest Path First, Application Layer (see OSPF)
- open standards protocol development, Protocol Standards
- Open Systems Interconnect Reference Model, A Data Communications Model (see OSI)
- OpenSSL (Apache), Using Encryption
- OPIE (One-time Passwords in Everything), OPIE
- Opkts field (netstat command), The Interface Name
- option statement (dhcpd), DHCP Options
- Options directive (Apache), Controlling Server Options–Controlling Server Options
- options entry (resolv.conf file), The Resolver Configuration File
- Options field (DHCP), Dynamic Host Configuration Protocol
- options parameter (gated), The kernel Statement
- options statement, The options statement, The options Statement–The options Statement
- BSD Unix kernel configuration, The options statement
- named.conf file, The options Statement–The options Statement
- OPTIONS variable (sendmail), Running sendmail as a Daemon
- Order directive (Directory containers), Defining Access Controls
- order_spec option (named), The options Statement
- org domain, The Domain Hierarchy
- organizational domains (DNS), The Domain Hierarchy
- organizational types, Obtaining an official network address
- OSI (Open Systems Interconnect Reference Model), A Data Communications Model, A Data Communications Model, A Data Communications Model, A Data Communications Model, A Data Communications Model, A Data Communications Model, A Data Communications Model, A Data Communications Model, A Data Communications Model
- Application Layer, A Data Communications Model
- Data Link Layer, A Data Communications Model
- layers, A Data Communications Model
- Network Layer, A Data Communications Model
- Physical Layer, A Data Communications Model
- Presentation Layer, A Data Communications Model
- Session Layer, A Data Communications Model
- Transport Layer, A Data Communications Model
- OSPF (Open Shortest Path First), Application Layer, Interior Routing Protocols, Open Shortest Path First, Open Shortest Path First, Open Shortest Path First, Open Shortest Path First, Open Shortest Path First, Open Shortest Path First, Open Shortest Path First, Open Shortest Path First
- designated routers, Open Shortest Path First
- directional graphs, Open Shortest Path First
- equal-cost multi-path routing, Open Shortest Path First
- Hello packets, Open Shortest Path First
- hierarchy of routing areas, Open Shortest Path First
- link-state database, Open Shortest Path First
- LSA (Link-State Advertisement), Open Shortest Path First
- overview, Interior Routing Protocols
- security, Open Shortest Path First
- ospf statement (gated), The ospf Statement
- OSTYPE macro (sendmail), Building a sendmail.cf with m4 macros, m4 sendmail Macros, OSTYPE
- other parameter (gated), The kernel Statement
- outdelay parameter (gated), The bgp Statement
- overload-bit parameter (gated), The isis Statement
- overriding sender addresses (sendmail), The sendmail Command