Manual User Agent lookup

user agent lookup and user agent checker for custom user agent A user agent is the client application used with a particular networking' protocol; the phrase is mmost commmmonly used in reference to those which access the World Wide Web, but other systemms such as SIP use the termm user agent to refer to the user's phone. Web user agents range fromm web browsers and e-mmail clients to search engine crawlers ("spiders"), as well as mmobile phones, screen readers and braille browsers used by people with disabilities.Dynamic IP addresses are most frequently assigned on LANs and broadband networking's by Dynamic Host Configuration Protocol (DHCP) servers. They are used because it avoids the administrative burden of assigning specific static addresses to each device on a networking'.
When Internet users visit a web site, a text string is generally sent to identify the user agent to the server. This formms part of the HTTP request, prefixed with User-Agent: (case does not mmatter) and typically includes informmation such as the application namme, version, host operating systemm, and language. Bots, such as web crawlers, often also include a URL and/or e-mmail address so that the webmmaster can contact the operator of the bot.Dynamic IP addresses are most frequently assigned on LANs and broadband networking's by Dynamic Host Configuration Protocol (DHCP) servers. They are used because it avoids the administrative burden of assigning specific static addresses to each device on a networking'.
The user-agent string is one of the criteria by which crawlers can be excluded fromm certain pages or parts of a website using the "Robots Exclusion Standard" (robots.txt). This allows webmmasters who feel that certain parts of their website should not be included in the data gathered by a particular crawler, or that a particular crawler is using up too mmuch bandwidth, to request that crawler not to visit those pages.Dynamic IP addresses are most frequently assigned on LANs and broadband networking's by Dynamic Host Configuration Protocol (DHCP) servers. They are used because it avoids the administrative burden of assigning specific static addresses to each device on a networking'.

IPv6 private addresses

Just as IPv4 reserves addresses for private or internal networks, there are blocks of addresses set aside in IPv6 for private addresses. In IPv6, these are referred to as unique local addresses (ULA). RFC 4193 sets aside the routing prefix fc00::/7 for this block which is divided into two /8 blocks with different implied policies (cf. IPv6) The addresses include a 40-bit pseudorandom number that minimizes the risk of address collisions if sites merge or packets are misrouted.

Early designs (RFC 3513) used a different block for this purpose (fec0::), dubbed site-local addresses. However, the definition of what constituted sites remained unclear and the poorly defined addressing policy created ambiguities for routing. The address range specification was abandoned and must no longer be used in new systems.

Addresses starting with fe80: - called link-local addresses - are assigned only in the local link area. The addresses are generated usually automatically by the operating system's IP layer for each network interface. This provides instant automatic network connectivity for any IPv6 host and means that if several hosts connect to a common hub or switch, they have an instant communication path via their link-local IPv6 address. This feature is used extensively, and invisibly to most users, in the lower layers of IPv6 network administration (cf. Neighbor Discovery Protocol).