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In August 1908, a white mob attacked Springfield, Illinois’s Black community, destroying homes and businesses and lynching two Black men. National outrage over the violence helped spur the movement that created the NAACP the following year.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
In Internet networking, a private network is a computer network that uses a private address space of IP addresses. These addresses are commonly used for local area networks (LANs) in residential, office, and enterprise environments. Both the IPv4 and the IPv6 specifications define private IP address ranges.
Most Internet service providers (ISPs) allocate only a single publicly routable IPv4 address to each residential customer, but many homes have more than one computer, smartphone, or other Internet-connected device. In this situation, a network address translator (NAT/PAT) gateway is usually used to provide Internet connectivity to multiple hosts. Private addresses are also commonly used in corporate networks which, for security reasons, are not connected directly to the Internet. Often a proxy, SOCKS gateway, or similar devices are used to provide restricted Internet access to network-internal users.
Private network addresses are not allocated to any specific organization. Anyone may use these addresses without approval from regional or local Internet registries. Private IP address spaces were originally defined to assist in delaying IPv4 address exhaustion. IP packets originating from or addressed to a private IP address cannot be routed through the public Internet.
Private addresses are often seen as enhancing network security for the internal network since use of private addresses internally makes it difficult for an external host to initiate a connection to an internal system.
The Internet Engineering Task Force (IETF) has directed the Internet Assigned Numbers Authority (IANA) to reserve the following IPv4 address ranges for private networks.[1]: 4 In practice, it is common to subdivide these ranges into smaller subnets.
| RFC 1918 name | IP address range | Number of addresses | Largest CIDR block (subnet mask) | Host ID size | Mask size | Classful description[Note 1] |
|---|---|---|---|---|---|---|
| 24-bit block | 10.0.0.0 – 10.255.255.255 | 16777216 | 10.0.0.0/8 (255.0.0.0) | 24 bits | 8 bits | single class A network |
| 20-bit block | 172.16.0.0 – 172.31.255.255 | 1048576 | 172.16.0.0/12 (255.240.0.0) | 20 bits | 12 bits | 16 contiguous class B networks |
| 16-bit block | 192.168.0.0 – 192.168.255.255 | 65536 | 192.168.0.0/16 (255.255.0.0) | 16 bits | 16 bits | 256 contiguous class C networks |
In April 2012, IANA allocated the 100.64.0.0/10 block of IPv4 addresses specifically for use in carrier-grade NAT scenarios.[3]
| IP address range | Number of addresses | Largest CIDR block (subnet mask) | Host ID size | Mask bits |
|---|---|---|---|---|
| 100.64.0.0 – 100.127.255.255 | 4194304 | 100.64.0.0/10 (255.192.0.0) | 22 bits | 10 bits |
This address block should not be used on private networks or on the public Internet. The size of the address block was selected to be large enough to uniquely number all customer access devices for all of a single operator's points of presence in a large metropolitan area such as Tokyo.[3]
The concept of private networks has been extended in the next generation of the Internet Protocol, IPv6, and special address blocks are reserved.
The address block fc00::/7 is reserved by IANA for unique local addresses (ULAs).[4] They are unicast addresses, but contain a 40-bit random number in the routing prefix to prevent collisions when two private networks are interconnected. Despite being inherently local in usage, the IPv6 address scope of unique local addresses is global.
The first block defined is fd00::/8, designed for /48 routing blocks, in which users can create multiple subnets, as needed.
| RFC 4193 Block | Prefix/L | Global ID (random) | Subnet ID | Number of addresses in subnet |
|---|---|---|---|---|
| 48 bits | 16 bits | 64 bits | ||
| fd00::/8 | fd | xx:xxxx:xxxx | yyyy | 18446744073709551616 |
Examples:
| Prefix/L | Global ID (random) | Subnet ID | Interface ID | Address | Subnet |
|---|---|---|---|---|---|
| fd | xx:xxxx:xxxx | yyyy | zzzz:zzzz:zzzz:zzzz | fdxx:xxxx:xxxx:yyyy:zzzz:zzzz:zzzz:zzzz | fdxx:xxxx:xxxx:yyyy::/64 |
| fd | 12:3456:789a | 0001 | 0000:0000:0000:0001 | fd12:3456:789a:1::1 | fd12:3456:789a:1::/64 |
A former standard proposed the use of site-local addresses in the fec0::/10 block, but because of scalability concerns and poor definition of what constitutes a site, its use has been deprecated since September 2004.[5]
Another type of private networking uses the link-local address range. The validity of link-local addresses is limited to a single link; e.g. to all computers connected to a switch, or to one wireless network. Hosts on different sides of a network bridge are also on the same link, whereas hosts on different sides of a network router are on different links.
In IPv4, the utility of link-local addresses is in zero-configuration networking when Dynamic Host Configuration Protocol (DHCP) services are not available and manual configuration by a network administrator is not desirable. The block 169.254.0.0/16 was allocated for this purpose.[6][7] If a host on an IEEE 802 (Ethernet) network cannot obtain a network address via DHCP, an address from 169.254.1.0 to 169.254.254.255[Note 2] may be assigned pseudorandomly. The standard prescribes that address collisions must be handled gracefully.
In IPv6, the block fe80::/10 is reserved for IP address autoconfiguration.[8] The implementation of these link-local addresses is mandatory, as various functions of the IPv6 protocol depend on them.[9]
A special case of private link-local addresses is the loopback interface. These addresses are private and link-local by definition since packets never leave the host device.
IPv4 reserves the entire class A address block 127.0.0.0/8 for use as private loopback addresses. IPv6 reserves the single address ::1.
An Internet Draft advocating reducing 127.0.0.0/8 to 127.0.0.0/16 was submitted in 2021;[10] it expired in 2025.[11]
It is common for packets originating in private address spaces to be misrouted onto the Internet. Private networks often do not properly configure DNS services for addresses used internally and attempt reverse DNS lookups for these addresses, causing extra traffic to the Internet root nameservers. The AS112 project attempted to mitigate this load by providing special black hole anycast nameservers for private address ranges which only return negative result codes (not found) for these queries.
Organizational edge routers are usually configured to drop ingress IP traffic for these networks, which can occur either by misconfiguration or from malicious traffic using a spoofed source address. Less commonly, ISP edge routers drop such egress traffic from customers, which reduces the impact to the Internet of such misconfigured or malicious hosts on the customer's network.
Since the private IPv4 address space is relatively small, many private IPv4 networks unavoidably use the same address ranges. This can create a problem when merging such networks, as some addresses may be duplicated for multiple devices. In this case, networks or hosts must be renumbered, often a time-consuming task or a network address translator must be placed between the networks to translate or masquerade one of the address ranges.
IPv6 defines unique local addresses,[4] providing a very large private address space from which each organization can randomly or pseudo-randomly allocate a 40-bit prefix, each of which allows 65536 organizational subnets. With space for about one trillion (1012) prefixes, it is unlikely that two network prefixes in use by different organizations would be the same, provided each of them was selected randomly, as specified in the standard. When two such private IPv6 networks are connected or merged, the risk of an address conflict is therefore virtually absent.
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
In Internet networking, a private network is a computer network that uses a private address space of IP addresses. These addresses are commonly used for local area networks (LANs) in residential, office, and enterprise environments. Both the IPv4 and the IPv6 specifications define private IP address ranges. Most Internet service providers (ISPs) allocate only a single publicly routable IPv4 address to each residential customer, but many homes have more than one computer, smartphone, or other Internet-connected device. In this situation, a network address translator (NAT/PAT) gateway is usually used to provide Internet connectivity to multiple hosts. Private addresses are also commonly used in corporate networks which, for security reasons, are not connected directly to the Internet. Often a proxy, SOCKS gateway, or similar devices are used to provide restricted Internet access to network-internal users. Private network addresses are not allocated to any specific organization. Anyone may use these addresses without approval from regional or local Internet registries. Private IP address spaces were originally defined to assist in delaying IPv4 address exhaustion. IP packets originating from or addressed to a private IP address cannot be routed through the public Internet. Private addresses are often seen as enhancing network security for the internal network since use of private addresses internally makes it difficult for an external host to initiate a connection to an internal system.
A virtual private network (VPN) is an overlay network that uses network virtualization to extend a private network across a public network, such as the Internet, via the use of encryption and tunneling protocols. In a VPN, a tunneling protocol is used to transfer network messages from one network host to another. Host-to-network VPNs are commonly used by organizations to allow off-site users secure access to an office network over the Internet. Site-to-site VPNs connect two networks, such as an office network and a datacenter. Provider-provisioned VPNs isolate parts of the provider's own network infrastructure in virtual segments, in ways that make the contents of each segment private with respect to the others. Individuals also use VPNs to encrypt and attempt to anonymize their network traffic, with VPN services selling access to their own private networks. VPNs can enhance usage privacy by making an ISP unable to access the private data exchanged across the VPN. However, the VPN provider and the online service being accessed via the VPN may have visibility of the user's activities. Through encryption, VPNs enhance confidentiality and reduce the risk of successful external data sniffing attacks.
A mobile virtual private network (mobile VPN or mVPN) is a VPN which is capable of persisting during sessions across changes in physical connectivity, point of network attachment, and IP address. The "mobile" in the name refers to the fact that the VPN can change points of network attachment, not necessarily that the mVPN client is a mobile phone or that it is running on a wireless network. Mobile VPNs are used in environments where workers need to keep application sessions open at all times, throughout the working day, as they connect via various wireless networks, encounter gaps in coverage, or suspend-and-resume their devices to preserve battery life. A conventional VPN cannot survive such events because the network tunnel is disrupted, causing applications to disconnect, time out, fail, or even the computing device itself to crash. Mobile VPNs are commonly used in public safety, home care, hospital settings, field service management, utilities and other industries. Increasingly, they are being adopted by mobile professionals and white-collar workers.
The Private Network-to-Network Interface (PNNI) is a link-state routing protocol used in Asynchronous Transfer Mode (ATM) networks. PNNI is similar to the Open Shortest Path First (OSPF) used for IP routing. PNNI is a suite of network protocols that can be used to discover an ATM network topology, create a database of topology information, and route calls over the discovered topology. PNNI is a link-state routing protocol, which means that the protocol collects information about the current state of links and nodes in the network to build a network database. The PNNI network database can be used to determine the network structure and the current state of network components. To build the PNNI network database, each PNNI node must receive topology information from all the other devices in the network. To keep the database current, the node must receive regular updates from other nodes. The PNNI protocol communicates the state of a PNNI network in PNNI Topology State Elements (PTSEs). PTSEs are discrete messages that contain information about one of the following types of network components: PNNI nodes Reachable addresses PNNI links between nodes To enable communications with other nodes, each switch needs to have all the PTSE information for each switch in the network. Each node is responsible for flooding out its own PTSE information to all the other switches in the network. Since up-to-date PTSE information is required for optimal routing decisions to be made, there are several different mechanisms in place to help ensure that all nodes have reasonably accurate PTSE information. The five common reasons for updating PTSEs are as follows: Resources administratively added, removed or altered on a node. Resource failure such as a loss of signal (LOS) on a link. A significant change in link resources due to virtual circuits (VCs) routing or derouting. Periodic updates defined by the PTSE refresh and PTSE lifetime interval timers. A processor switch module (PXM) switchover. PTSE information is passed between nodes using PNNI topology state packets (PTSPs). These packets utilize the routing control channel (RCC; VPI = 0 and VCI = 18) between adjacent nodes. The RCC is also used for Hello packets and other PNNI messages. If the switch is unable to establish the RCC with the adjacent node, then PTSE information is not exchanged. Once a node receives PTSE information, the node stores the contents, or element information, in the database. This information is used to generate precomputed routing tables that identify routes to other network devices. PNNI uses the Dijkstra's algorithm for shortest path first (SPF) calculation. The PNNI database is also used to perform on-demand routing when the appropriate routing table does not contain a viable path. PNNI measures line capacities and delays in addition to simple cost metrics.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Brown v. Board of Education in 1954.