gated_intro(7)gated_intro(7)NAMEgated_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 pur‐
pose of exchanging routing information. Not every pair of neighboring
routers becomes adjacent. A set of routers under a single technical
administration, using an interior gateway protocol and common metrics
to route packets within the AS, and using an exterior gateway protocol
to route packets to other ASs. Since this classic definition was devel‐
oped, 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
administration 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 repre‐
sented 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 maxi‐
mum 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 network and assists
in running the protocol. The designated router is elected by the
HELLO protocol. Any network or host. An EGP metric. See met‐
ric and EGP. Valid values are from zero to 255 inclusive. A
class of routing protocols used to exchange routing information
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 destina‐
tion by which packets are delivered to their ultimate destina‐
tion. 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, inclu‐
sive, separated by dots (.). For example 132.236.199.63 or
10.0.0.51. It can also be specified as an eight digit hexadeci‐
mal string preceded by 0x. For example, 0x0a000043. In addi‐
tion, 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 configu‐
ration 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
autonomous 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 num‐
ber) 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 inter‐
face. 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 significant 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 influence
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 pro‐
tocol (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 (milliseconds) 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 estab‐
lished 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 multiaccess networks,
routers are dynamically discovered by OSPF's HELLO protocol.
Any packet-switched network. A network may be specified by its
IP address or network name. The host bits in a network specifi‐
cation must be zero. Default may be used to specify the default
network (0.0.0.0). The IP address of a network. Usually speci‐
fied 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 speci‐
fied, 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 usually 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) pref‐
erence 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 identi‐
fies the router within the autonomous system. An IP address
used as unique identifier assigned to represent a specific
router. This is usually 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 capa‐
ble 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
following forms: A non-negative decimal number of seconds. For
example, 27, 60, or 3600. A non-negative decimal number of min‐
utes followed 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 val‐
ues are from one (1) through 255, inclusive. The type of ser‐
vice is for internet service quality selection. The type of
service is specified along the abstract parameters precedence,
delay, throughput, reliability, and cost. These abstract param‐
eters 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.
SEE ALSO
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 Proto‐
col (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
gated_intro(7)