gated_intro(7) Miscellaneous Information Manual gated_intro(7)
NAME
gated_intro - Information about the gate daemon and its implementation
DESCRIPTION
This reference page contains a glossary of terms that are used in any discussion of gated and the gated.conf file.
GLOSSARY
A relationship formed between selected neighboring routers for the purpose of exchanging routing information. Not every pair of neighbor-
ing routers becomes adjacent. A set of routers under a single technical administration, using an interior gateway protocol and common met-
rics to route packets within the AS, and using an exterior gateway protocol to route packets to other ASs. Since this classic definition
was developed, it has become common for a single AS to use several interior gateway protocols and sometimes several sets of metrics within
an AS.
The use of the term "autonomous system" stresses that even when multiple internal gateway protocols and metrics are used, the admin-
istration of an AS appears to other ASs to have a single coherent interior routing plan and presents a consistent picture of what
networks are reachable through it. The AS is represented by a number between 1 and 65534, assigned by the Internet Assigned Numbers
Authority. One of a class of exterior gateway protocols, described in more detail in the BGP section of gated.proto(4). An OSPF
(Open Shortest Path First) protocol metric. See metric and OSPF. A HELLO metric. Valid values are from zero to 30000, inclusive.
The value of 30000 is the maximum metric and means unreachable. See metric and HELLO. In OSPF, a designated router is a multiaccess
network that has at least two attached routers. The designated router generates a link state advertisement for the multiaccess net-
work and assists in running the protocol. The designated router is elected by the HELLO protocol. Any network or host. An EGP met-
ric. See metric and EGP. Valid values are from zero to 255 inclusive. A class of routing protocols used to exchange routing infor-
mation within an autonomous system. A detailed explanation of exterior gateway protocols is available in gated.proto(4). One of a
class of exterior gateway protocols, described in more detail in the EGP section of gated.proto(4). 1. An intermediate destination
by which packets are delivered to their ultimate destination. 2. A host address of another router that is directly reachable via an
attached network. As with any host address it may be specified symbolically. A list of one or more gateways separated by white
space. One of a class of interior gateway protocols, described in more detail in the HELLO section of gated.proto(4). The IP
address of any system, usually specified as a dotted quad (four values in the range of 0 to 255, inclusive, separated by dots (.).
For example 132.236.199.63 or 10.0.0.51. It can also be specified as an eight digit hexadecimal string preceded by 0x. For exam-
ple, 0x0a000043. In addition, if the options noresolv statement is not specified, this can be a symbolic host name. For example,
gated.cornell.edu or nic.ddn.mil. The numeric forms are preferred over the symbolic form. The host address of an attached network
interface. This is the address of a broadcast, nbma, or loopback interface, and the remote address of a point-to-point interface.
As with any host address it can be specified symbolically. The connection between a router and one of its attached networks. A
physical interface may be specified by a single IP address, domain name, or interface name. (Unless the network is an unnumbered
point-to-point network.) Multiple levels of reference in the configuration language allow identification of interfaces using wild
card, interface type name, or delete word address. Be careful with the use of interface names as future versions might allow more
than one address per interface. Dynamic interfaces can be added or deleted and indicated as up or down as well as changes to
address, netmask and metric parameters. One of a class of routing protocols used to exchange routing information within an autono-
mous system. A detailed explanation of interior gateway protocols is available in gated.proto(4). A list of one or more interface
names, including wildcard names (names without a number) and names that may specify more than one interface or address, or the token
all for all interfaces. See gated.conf(4) for more information. The host address of an attached interface. This is the address of
a broadcast, nbma, or loopback interface, and the local address of a point-to-point interface. As with any host address it may be
specified symbolically. A means of subdividing networks using address modification. A mask is a dotted quad specifying the bits of
the destination that are significant. Except when used in a route filter, gated only supports contiguous masks. The number of sig-
nificant bits in the mask. One of the units used to help a system determine the best route. Metrics may be based on hop count,
routing delay, or an arbitrary value set by the administrator depending on the type of routing protocol. Routing metrics may influ-
ence the value of assigned internal preferences. (See preference.)
The following sample table shows the range of possible values for each routing protocol metric and the value used by each protocol
(See gated.proto(4)) to reach a destination: SAMPLE ROUTING PROTOCOL METRICS Protocol Metric Represents Range Unreachable
-------- ----------------- ----- ----------- RIP distance (hop-count) 0-15 16 HELLO delay (millisec-
onds) 0-29999 30000 OSPF cost of path 0-????? Delete EGP distance (unused) 0-65535 255 BGP
unspecified 0-65534 65535 Those physical networks that support the attachment of multiple (more than two) routers.
Each pair of routers on such a network is assumed to be able to communicate directly. Another router with which implicit or
explicit communication is established by a routing protocol. Neighbors are usually on a shared network, but not always. This term
is mostly used in OSPF and EGP. Usually synonymous with peer. Two routers that have interfaces to a common network. On multiac-
cess networks, routers are dynamically discovered by OSPF's HELLO protocol. Any packet-switched network. A network may be speci-
fied by its IP address or network name. The host bits in a network specification must be zero. Default may be used to specify the
default network (0.0.0.0). The IP address of a network. Usually specified as a dotted quad, one to four values in the range of 0
to 255 inclusive separated by dots (.). For example, 132.236.199, 132.236, or 10. It may also be specified as a hexadecimal string
preceded by 0x with an even number of digits between two and eight. For example, 0x??????, 0x???? or 0x0a. Also allowed is the
symbolic value default that has the value 0.0.0.0, the default network. If options noresolv statement is not specified, this can
also be a symbolic network name. For example,nr-tech-prod, cornellu-net, and arpanet. The numeric forms are preferred over the
symbolic form. A positive integer. One of a class of interior gateway protocols, described in more detail in the OSPF section of
gated.proto(4). Another router with which implicit or explicit communication is established by a routing protocol. Peers are usu-
ally on a shared network, but not always. This term is mostly used by BGP. Usually synonymous with neighbor. A UDP or TCP port
number. Valid values are from 1 through 65535 inclusive. A preference is a value between 0 (zero) and 255 used to select between
many routes to the same destination. The route with the best (numerically lowest) preference is selected as the active route. The
active route is the one installed in the kernel forwarding table and exported to other protocols. Preference zero is usually
reserved for routes to directly attached interfaces. A default preference is assigned to each source from which gated receives
routes. (See Preference.) A contiguous mask covering the most significant bits of an address. The prefix length specifies how many
bits are covered. The OSI equivalent of TOS. One of a class of interior gateway protocols, described in more detail in the RIP
section of gated.proto(4). A 32-bit number assigned to each router running the OSPF protocol. This number uniquely identifies the
router within the autonomous system. An IP address used as unique identifier assigned to represent a specific router. This is usu-
ally the address of an attached interface. The repository of all of gated's retained routing information, used to make decisions
and as a source for routing information that is propagated. An interface may be marked as simplex either by the kernel, or by
interface configuration. A simplex interface is an interface on a broadcast media that is not capable of receiving packets it
broadcasts.
The gated daemon takes advantage of interfaces that are capable of receiving their own broadcast packets to monitor whether an
interface appears to be functioning properly. A time value, usually a time interval. It may be specified in any one of the follow-
ing forms: A non-negative decimal number of seconds. For example, 27, 60, or 3600. A non-negative decimal number of minutes fol-
lowed by a seconds value in the range of zero to 59, inclusive. For example, 0:27, 1:00, or 60:00. A non-negative decimal number
of hours followed by a minutes value in the range of zero to 59, inclusive, followed by a seconds value in the range of zero to 59,
inclusive. For example, 0:00:27, 0:01:00, or 1:00:00. The Time To Live (TTL) of an IP packet. Valid values are from one (1)
through 255, inclusive. The type of service is for internet service quality selection. The type of service is specified along the
abstract parameters precedence, delay, throughput, reliability, and cost. These abstract parameters are to be mapped into the
actual service parameters of the particular networks the datagram traverses. The vast majority of IP traffic today uses the default
type of service.
RELATED INFORMATION
Daemons: gated(8).
Files: gated.conf(4), gated.control(4), gated.proto(4).
RFC 827, Exterior Gateway Protocol EGP, E. Rosen.
RFC 891, DCN local-network protocols, D. Mills.
RFC 904, Exterior Gateway Protocol Formal Specification, D. Mills.
RFC 1058, Routing Information Protocol, C. Hedrick.
RFC 1105, Border Gateway Protocol BGP, K. Lougheed, Y. Rekhter.
RFC 1163, A Border Gateway Protocol (BGP), K. Lougheed, Y. Rekhter.
RFC 1164, Application of the Border Gateway Protocol in the Internet, J. Honig, D. Katz, M. Mathis, Y. Rekhter, J. Yu.
RFC 1227, SNMP MUX Protocol and MIB, M. Rose.
RFC 1245, OSPF Protocol Analysis, J. Moy.
RFC 1246, Experience with the OSPF Protocol, J. Moy.
RFC 1253, OSPF Version 2 Management Information Base, F. Baker, R. Coltun.
RFC 1256, ICMP Router Discovery Messages, S. Deering.
RFC 1265, BGP Protocol Analysis, Y. Rekhter.
RFC 1266, Experience with the BGP Protocol, Y. Rekhter.
RFC 1267, A Border Gateway Protocol 3 (BGP-3), K. Lougheed, Y. Rekhter.
RFC 1268, Application of the Border Gateway Protocol in the Internet, P. Gross, Y. Rekhter.
RFC 1269, Definitions of Managed Objects for the Border Gateway Protocol (Version 3), J. Burruss, S. Willis.
RFC 1321, The MD5 Message-Digest Algorithm, R. Rivest.
RFC 1370, Internet Architecture Board Applicability Statement for OSPF
RFC 1388, RIP Version 2 Carrying Additional Information, G. Malkin.
RFC 1397, Default Route Advertisement In BGP2 And BGP3 Versions Of The Border Gateway Protocol, D. Haskin.
RFC 1403, BGP OSPF Interaction, K. Varadhan.
RFC 1583, OSPF Version 2, J. Moy. delim off
gated_intro(7)