[Appendix B] A gated Reference
Traces the list of interfaces read from the kernel. Use this to determine what interfaces
are detected by the kernel interface scan.
The advantage of placing a trace option on the command line is that it can trace activities that happen
before the configuration file is processed. For the two options listed above, this is an essential
advantage. For other options it is not very important. Most trace options are specified in the
configuration file. See the traceoptions command later in this appendix for more details.
B.1.1 Signal Processing
gated processes the following signals:
SIGHUP
Tells gated to reread the configuration file. The new configuration replaces the one that gated
is currently running. SIGHUP loads the new configuration file without interrupting gated
service. SIGHUP is available for quick configuration changes. At most sites, the routing
configuration changes infrequently. The few times you need to change to a new configuration,
terminate gated and rerun it with the new configuration. This is a more accurate test of how
things will run at the next boot.
SIGINT
Tells gated to snapshot its current state to the file /usr/tmp/gated_dump.
SIGTERM
Tells gated to shut down gracefully. All protocols are shut down following the rules of that
protocol. For example, EGP sends a CEASE message and waits for it to be confirmed.
SIGTERM removes from the kernel routing table all routes learned via the exterior routing
protocols. If you need to preserve those routes while gated is out of operation, use SIGKILL.
SIGKILL
Tells gated to terminate immediately and dump core. Routes are not removed from the routing
table, and no graceful shutdown is attempted.
SIGUSR1
Tells gated to toggle tracing. If no trace flags are set, SIGUSR1 has no effect. But if tracing is
enabled, the first SIGUSR1 causes gated to toggle off tracing and to close the trace file. The
next SIGUSR1 turns tracing back on and opens the trace file. When the trace file is closed, it
can be moved or removed without interfering with the operation of gated. Use this to

periodically empty out the trace file to prevent it from becoming too large.
SIGUSR2
Tell gated to check for changes in the status of the network interfaces.
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[Appendix B] A gated Reference
The following is an example of gated signal handling. First, the SIGUSR1 signal is passed to the
gated process using the process ID obtained from the gated.pid file (/var/run/gated.pid in this case).
# kill -USR1 `cat /var/run/gated.pid`
Next, the old trace file (/usr/tmp/gated.log in this case) is removed, and gated is passed another
SIGUSR1 signal.
# rm /usr/tmp/gated.log
# kill -USR1 `cat /etc/gated.pid`
After receiving the second signal, gated opens a fresh trace file (still named /usr/tmp/gated.log). An ls
shows that the new file has been created.
# ls -l /usr/tmp/gated.log
-rw-rw-r-- 1 root 105 Jul 6 16:41 /usr/tmp/gated.log
Previous: A.3 chat
TCP/IP Network
Administration
Next: B.2 The gated
Configuration Language
A.3 chat
Book Index
B.2 The gated Configuration
Language
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[Appendix B] B.2 The gated Configuration Language

Previous: B.1 The gated
Command
Appendix B
A gated Reference
Next: B.3 Directive
Statements

B.2 The gated Configuration Language
The gated configuration language is a highly structured language similar to C in appearance.
Comments either begin with a #, or they begin with /* and end with */. gated configuration
statements end with a semicolon, and groups of associated statements are enclosed in curly braces.
The language structure is familiar to most UNIX system administrators, and the structure makes it
easy to see what parts of the configuration are associated with each other. This is important when
multiple protocols are configured in the same file.
The configuration language is composed of nine types of statements. Two statement types, directive
statements and trace statements, can occur anywhere in the gated.conf file and do not directly relate to
the configuration of any protocol. These statements provide instructions to the parser and control
tracing from within the configuration file. The other seven statement types are options statements,
interface statements, definition statements, protocol statements, static statements, control statements,
and aggregate statements. These statements must appear in the configuration file in the correct order,
starting with options statements and ending with aggregate statements. Entering a statement out of
order causes an error when parsing the file.
The remainder of this appendix provides a description of all commands in the gated configuration
language, organized by statement type.
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Command
TCP/IP Network
Administration
Next: B.3 Directive
Statements

B.1 The gated Command
Book Index
B.3 Directive Statements
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[Appendix B] B.3 Directive Statements
Previous: B.2 The gated
Configuration Language
Appendix B
A gated Reference
Next: B.4 Trace Statements

B.3 Directive Statements
Directive statements provide direction to the gated command language parser about "include" files.
An include file is an external file whose contents are parsed into the configuration as if it were part of
the original gated.conf file. Include files can contain references to other include files, and these
references can be nested up to 10 levels deep.
The two directive statements are:
%include filename
Identifies an include file. The contents of the file are "included" in the gated.conf file at the
point in the gated.conf file where the %include directive is encountered. filename is any
valid UNIX filename. If filename is not fully qualified, i.e., does not begin with a /, it is
considered to be relative to the directory defined in the %directory directive.
%directory pathname
Defines the directory where the include files are stored. When it is used, gated looks in the
directory identified by pathname for any include file that does not have a fully qualified
filename.
Unless you have a very complex routing configuration, avoid using include files. In a complex
environment, segmenting a large configuration into smaller, more easily understood segments can be

helpful, but most gated configurations are very small. One of the great advantages of gated is that it
combines the configuration of several different routing protocols into a single file. If that file is small
and easy to read, segmenting the file unnecessarily complicates things.
Previous: B.2 The gated
Configuration Language
TCP/IP Network
Administration
Next: B.4 Trace Statements
B.2 The gated Configuration
Language
Book Index
B.4 Trace Statements
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[Appendix B] B.3 Directive Statements
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Previous: B.3 Directive
Statements
Appendix B
A gated Reference
Next: B.5 Options
Statements

B.4 Trace Statements
Trace statements allow you to control the trace file and its contents from within the gated.conf file.
The trace statement is:
traceoptions ["trace_file" [replace] [size bytes[k|m] files n]] [nostamp] trace_options

[except trace_options] ;
Its components are as follows:
trace_file
Identifies the file that receives the trace output. It has exactly the same function as the
trace_file argument on the gated command line.
replace
Replaces the existing trace file. If you do not use this keyword, the trace output is appended to
the current contents of the file.
size bytes[k|m] [files n]
Limits the trace file to a maximum size of bytes. The optional k or m indicates thousands (k)
or millions (m) of bytes. Thus 1000000 and 10m are equivalent entries. The size of the trace
file cannot be less than 10k bytes. n defines the maximum number of trace files that should be
saved. When the trace file reaches the maximum size, it is saved as trace_file.0,
trace_file.1, trace_file.2 up to trace_file.n. The next save then overwrites
trace_file.0. The value for n must be at least 2.
nostamp
Specifies that trace lines should not begin with a timestamp. Timestamping each line of trace
data is the default.
trace_options
Define the events to be traced by gated. Each trace option is specified by a keyword name. The
available trace options are:
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none
Turns off all tracing.
all
Turns on all types of global tracing.
general
Turns on both normal and route tracing.

state
Traces state machine transitions for protocols such as OSPF and BGP. The RFCs
describe these protocols using finite state machine (FSM) diagrams or tables. The
protocols transition from one state to another based on the occurrence of certain events.
For example, the state might change from idle to connect when a connection open event
occurs. This is a highly specialized trace flag, useful only to those who have a thorough
understanding of the protocols involved. Use this option within the protocol statement
to trace a specific protocol's transitions.
normal
Traces normal protocols interactions. Errors are always traced.
policy
Traces the application of routing policies. Use this to check that you have properly
configured your routing policy.
task
Traces system-level processing.
timer
Traces the various timers used by a protocol or peer.
route
Traces routing table changes. Use this to check that routes are properly installed by the
protocol.
detail
Traces the contents of the packets exchanged by the router. Must be specified before
send or recv.
send
Limits the detail trace to packets sent by this router.
recv
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Limits the detail trace to packets received by this router. Without these two options, all

packets are traced when detail is specified.
symbols
Traces the symbols read from the kernel at startup. See the -t command-line argument.
iflist
Traces the kernel interface list. See the -t command-line argument.
parse
Traces the lexical analyzer and parser.
adv
Traces the allocation and release of blocks.
except trace_options
Disables specific trace options. Must be used in conjunction with trace_options that
enable a wide variety of tracing. For example: traceoptions all except state
turns on all traces except for finite state machine tracing.
gated provides the flexibility for you to choose where you want to control tracing - on the command
line or in the configuration file. By and large, the same trace options can be set on the gated command
line or in the configuration file. detail, send and recv can be set only in the configuration file.
Two others, symbols and iflist, are primarily used on the command line. Refer to the section on the
gated command line for a description of setting trace options with -t.
Some trace options are only useful for protocol developers and other experts. For most of us, general,
which enables normal and route tracing, is an appropriate level of information for debugging routing
problems. Occasionally policy is useful for testing a routing policy. Most of the time, however, no
tracing is needed.
Previous: B.3 Directive
Statements
TCP/IP Network
Administration
Next: B.5 Options
Statements
B.3 Directive Statements
Book Index

B.5 Options Statements
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[Appendix B] B.5 Options Statements
Previous: B.4 Trace
Statements
Appendix B
A gated Reference
Next: B.6 Interface
Statements

B.5 Options Statements
Options statements define parameters that direct gated to do special internal processing. Options
statements appear before any other configuration statements in the gated.conf file.
The options statement syntax is:
options
[nosend]
[noresolv]
[gendefault [preference preference] [gateway gateway]]
[syslog [upto] log_level]
[mark time]
;
An options statement can contain:
nosend
Instructs system not to send any packets. This option tests gated without actually sending out
routing information. Use for RIP and HELLO. It is not yet implemented for BGP and is not
useful for OSPF.
noresolv
Instructs system not to use the Domain Name System (DNS) to resolve hostnames and

addresses. DNS failures can cause gated to deadlock during startup. Use this to prevent
deadlock.
gendefault [preference preference] [gateway gateway]
Generates a default route, with a preference of 20, when gated peers with an EGP or BGP
neighbor. If gateway is not defined, the gateway in the generated route is the system itself; the
default route is not installed in the kernel table; and it is used only to advertise this system as a
default gateway. If gateway is specified, the default route is installed in the kernel table with
the specified router as the next hop. This option can be overridden with the nogendefault
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[Appendix B] B.5 Options Statements
option.
syslog [upto] log_level
Tells system to use the setlogmask facility to control gated logging. See the setlogmask(3)
manpage if this facility is available on your system.
mark time
Sends a periodic timestamp message to the trace file. time defines how frequently the
timestamp should be issued. Use this to determine if gated is running.
Previous: B.4 Trace
Statements
TCP/IP Network
Administration
Next: B.6 Interface
Statements
B.4 Trace Statements
Book Index
B.6 Interface Statements
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[Appendix B] B.6 Interface Statements
Previous: B.5 Options
Statements
Appendix B
A gated Reference
Next: B.7 Definition
Statements

B.6 Interface Statements
An interface statement defines configuration options for the network interfaces. The
interface_list identifies the interfaces affected by the configuration options. The interfaces in
the list are identified by interface name (e.g., le0), by hostname, by IP address, or by the keyword all.
The keyword all refers to every interface on the system. The interface name can refer to a single
interface or a group of interfaces. For example, an interface name of eth0 refers to the interface eth0,
whereas the name le refers to all installed interfaces that start with the letters le (which might include
le0, le1, and le2). A hostname can be used if it resolves to only one address.
Most system administrators prefer to use the IP address to identify an interface. After all, IP addresses
are inherently a part of TCP/IP, and it's TCP/IP routing that this file configures.
Additionally, remote systems know this interface by its IP address, not its interface name. Finally,
DNS may provide more than one address for a hostname, and future UNIX operating systems may
allow more than one address per interface. IP addresses are safest.
gated supports four types of interfaces: loopback, broadcast, point-to-point, and non-broadcast multi-
access (NBMA). All of these are discussed in the text of this book except for NBMA. It is a multi-
access interface, but the underlying network is not capable of broadcast. Examples are frame relay and
X.25.
gated ignores any interface in the list that has an invalid local, remote, or broadcast address, or an
invalid subnet mask. gated also ignores a point-to-point interface that has the same local and remote
addresses. gated assumes that interfaces that are not marked UP by the kernel do not exist.
The syntax of the interfaces statement is:
interfaces {

options
[strictinterfaces]
[scaninterval time] ;
interface interface_list
[preference preference]
[down preference preference]
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[Appendix B] B.6 Interface Statements
[passive]
[simplex]
[reject]
[blackhole] ;
define address
[broadcast address] | [pointtopoint address]
[netmask mask]
[multicast] ;
} ;
The configuration options defined before the interface list are global options. The global options are:
strictinterfaces
Generates a fatal error if an interface is referenced in the configuration file that is not found
when gated scans the kernel at startup and is not listed in a define statement. (See the define
option later in this section.) Normally a warning message is issued and gated continues
running.
scaninterval time
Specifies how often gated scans the kernel interface list for changes. The default is every 15
seconds on most systems, and 60 seconds on systems that pass interface status changes through
the routing socket, e.g., BSD 4.4. Note that gated also scans the interface list on receipt of a
SIGUSR2.
The interface command defines the interface_list and all of the options that affect the

specified interfaces. Options available on this statement are:
preference preference
Sets the preference for this interface. The value preference is a number between 0 and 255.
gated prefers routes through interfaces with low preference numbers. The default preference
for all directly attached network interfaces is 0.
down preference preference
Sets the preference used when gated believes an interface is not functioning properly. The
default is 120.
passive
Prevents gated from downgrading the preference of the interface when it is not functioning
properly. gated assumes that an interface is down when it stops receiving routing information
through that interface. gated only performs this check if the interface is actively participating
in a routing protocol.
simplex
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[Appendix B] B.6 Interface Statements
Specifies that gated should not use packets generated by this system as an indication that the
interface is functioning properly. Only packets from remote systems are used to indicate that
the interface is operating.
reject | blackhole
Either of these keywords identifies the interface as the "blackhole interface" used to install
rejected routes in the kernel. (See the control statements for more about rejected routes.) This
is available only on BSD systems that have installed a reject/blackhole pseudo-interface.
The define address command lists interfaces that might not be present when gated scans the kernel
interface list at startup. It overrides the strictinterfaces option for the interface defined by address.
Possible options for the define command are:
broadcast address
Defines the broadcast address.
pointopoint address

Defines the local address for a point-to-point interface. (See
Chapter 6, Configuring the
Interface for a discussion of point-to-point interfaces.) When this option is used, the address on
the define statement specifies the address of the remote host, and the address specified after the
pointopoint keyword defines the local address. Don't use both broadcast and pointopoint in
the same define.
netmask mask
Defines the subnet mask.
multicast
Specifies that the interface supports multicasting.
Previous: B.5 Options
Statements
TCP/IP Network
Administration
Next: B.7 Definition
Statements
B.5 Options Statements
Book Index
B.7 Definition Statements
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[Appendix B] B.7 Definition Statements
Previous: B.6 Interface
Statements
Appendix B
A gated Reference
Next: B.8 Protocol
Statements


B.7 Definition Statements
Definition statements are general configuration statements that relate to more than one protocol.
Definition statements must appear before any protocol statements in gated.conf. The three definition
statements are:
autonomoussystem asn [loops n] ;
Defines the autonomous system number (asn) used by BGP or EGP. The loops number
defines the number of times this autonomous system may appear in an AS path for path vector
protocols, such as BGP. The default value for n is 1.
routerid address ;
Defines the router identifier used by BGP and OSPF. Use the address of your primary OSPF or
BGP interface. By default, gated uses the address of the first interface it encounters.
martians {
host address [allow];
address [mask mask | masklen number] [allow] ;
default [allow] ;
} ;
Changes the list of addresses about which all routing information is ignored. Sometimes a
misconfigured system sends out obviously invalid destination addresses. These invalid addresses,
called martians, are rejected by the routing software. This command allows changes to the list of
martian addresses. A martian address can be specified as a host address by using the host keyword
before the address, or as a network address by simply specifying the address.
An address mask can be defined for a network address. The mask can be defined in dotted decimal
notation using the mask keyword or as a numeric prefix length using the masklen keyword. The
address masks mask 255.255.0.0 and masklen 16 are equivalent. If no address mask is
specified, the natural mask is used. Specifying an address in the martians statement adds the address
to the martians list. The allow keyword is used to remove an address from the martians list. When an
address is removed from the martians list, it then becomes a valid address for routing.
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[Appendix B] B.7 Definition Statements

gated contains a standard martian list of addresses that are known to be invalid. This is the default
martian list. The option default allow removes all of the standard entries from the martians list and
permits unrestricted routing. Don't do this if you're on a connected network.
Here is a sample of each definition statement:
autonomoussystem 249 ;
routerid 172.16.12.2 ;
martians {
host 0.0.0.26 ;
192.168.0.0 masklen 16 allow ;
} ;
The statements in the sample perform the following functions:
●
The autonomoussystem statement tells gated to use AS number 249 for its BGP or EGP
packets.
●
The routerid statement tells gated to use 172.16.12.2 as the router identifier for OSPF and
BGP.
●
The martians statement prevents routes to 0.0.0.26 from being included in the table, but it
allows routes to the private IP addresses in the range 192.168.0.0 to 192.168.255.255.
Previous: B.6 Interface
Statements
TCP/IP Network
Administration
Next: B.8 Protocol
Statements
B.6 Interface Statements
Book Index
B.8 Protocol Statements
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[Appendix B] B.8 Protocol Statements
Previous: B.7 Definition
Statements
Appendix B
A gated Reference
Next: B.9 static Statements

B.8 Protocol Statements
Protocol statements enable or disable protocols and set protocol options. The protocol statements
occur after the definition statements and before the static statements. There are many protocol
statements and more may be added at any time. There are statements for the various interior and
exterior routing protocols, and for other things that are not really routing protocols.
In this section we begin with the interior protocols, move on to the exterior protocols, and finish with
the special "protocols."
B.8.1 The ospf Statement
ospf yes | no | on | off [{
defaults {
preference preference ;
cost cost ;
tag [as] tag ;
type 1 | 2 ; } ;
exportlimit routes ;
exportinterval time ;
traceoptions trace_options ;
monitorauthkey password ;
backbone | area number {
authtype 0 | 1 | none | simple ;
stub [cost cost] ;

networks {
address [mask mask |masklen number] [restrict] ;
host address [restrict] ; } ;
stubhosts {
address cost cost ; } ;
interface interface_list [nonbroadcast] [cost cost] {
pollinterval time ;
routers {
address [eligible] ; } ;
interface_parameters } ;
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[Appendix B] B.8 Protocol Statements
virtuallink neighborid router_id transitarea area {
interface_parameters } ;
} ;
} ] ;
The ospf statement enables or disables the Open Shortest Path First (OSPF) routing protocol. By
default, OSPF is disabled. It is enabled by specifying yes or on (it doesn't matter which you use) and it
is disabled with no or off.
NOTE: For the sake of brevity, this text explains only the first occurrence of any
gated.conf parameter if it is used the same way in subsequent commands. Only
differences between commands are explained. For example, yes | no | on | off is not
explained again, because it is always used in the same way to enable or disable a
protocol.
The ospf statement has many configuration parameters:
defaults
Defines the defaults used when importing OSPF routes from an external autonomous system
and announcing those routes to other OSPF routers. The link-state advertisement (LSA) used to
announce these routes is called an ASE (autonomous system external) because it contains

routes from external autnomous systems. See the description of OSFP in
Chapter 7.
preference preference
Defines the preference of OSPF ASE routes. The default is 150.
cost cost
Defines the cost used when advertising a non-OSPF route in an ASE. The default is 1.
tag [as] tag
Defines the OSPF ASE tag value. The tag is not used by the OSPF protocol, but may be
used by an export policy to filter routes. (See the export statement later in this
appendix.) When the as keyword is specified, the tag field may contain AS path
information.
type 1 | 2
Defines the type of ASE used. The default is type 1. Type 1 contains routes learned from
an external protocol that provides a metric directly comparable to the OSPF metric. The
metric is added to the cost of reaching the border router when routes are advertised. A
type 2 ASE contains routes learned from an exterior gateway protocol that does not
provide a routing metric comparable to the OSPF metric. These routes are advertised
with the cost of reaching the border router. See
Chapter 7.
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[Appendix B] B.8 Protocol Statements
exportlimit routes
Defines the maximum number of ASE LSAs that will be flooded at one time. The default is
100.
exportinterval time
Defines how frequently ASE link-state advertisements are flooded to the network. The default
is once per second.
traceoptions trace_options
Defines the tracing used to debug OSPF. In addition to the standard trace flags, OSPF supports:

lsabuild
Traces construction of link-state advertisements (LSA).
spf
Traces the Shortest Path First (SPF) calculations.
hello
Traces the OSPF HELLO packets.
dd
Traces the OSPF Database Description packets.
request
Traces the OSPF Link-State Request packets.
lsu
Traces the OSPF Link-State Update packets.
ack
Traces OSPF Link-State Ack packets.
monitorauthkey password
Defines the password used for ospf_monitor queries. By default these queries are not
authenticated. If monitorauthkey is specified, incoming queries must contain the specified
password.
backbone | area number
Defines the OSPF area of which this router is a member. Every router must belong to an area. If
more than one area is configured, at least one must be the backbone. The backbone is defined
using the backbone keyword. All other areas are defined by the area keyword and the number
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[Appendix B] B.8 Protocol Statements
of the area, e.g., area 1. See Chapter 7 for a discussion of OSPF areas. Several configuration
parameters are associated with each area:
authtype 0 | 1 | none | simple
Specifies the authentication scheme used in this area. The authentication schemes can be
defined by none or 0 for no authentication, or simple or 1 for password authentication.

Each system in an area must use this same authentication scheme.
stub [cost cost]
Specifies that this is a stub area. A stub area is one in which there are no ASE routes. If
a cost is specified, it is used to advertise a default route into the stub area.
networks
Defines the range of networks contained within this area. The specified ranges are
advertised into other areas as summary network LSAs and not as inter-area routes. If
restrict is specified, the summary network LSAs are not advertised. The entries in the
networks list are either specified as host addresses by using the host keyword before the
address, or as a network address by simply specifying the address. An address mask can
be defined for a network address. The mask can be defined in dotted decimal notation
using the mask keyword or as a numeric prefix length using the masklen keyword. The
address masks mask 255.255.0.0 and masklen 16 are equivalent. If no address
mask is specified, the natural mask is used. This option can reduce the amount of
routing information propagated between areas.
stubhosts
Lists the directly attached hosts, and their costs, that should be advertised as reachable from
this router. List point-to-point interfaces here.
interface interface_list [nobroadcast] [cost cost]
Defines the interfaces used by OSPF. If the keyword nobroadcast is specified, the interface
connects to a non-broadcast multi-access (NBMA) network. If nobroadcast is not used, the
interface connects to a broadcast or a point-to-point network. Specify the cost of the interface
with the cost keyword, e.g., cost 5. The default cost is 1. Two options are specific to NBMA
interfaces:
pollinterval time
Defines the time interval at which OSPF HELLO packets are sent to neighbors.
routers
Lists all neighbors by address. The eligible keyword indicates if the neighbor can
become a designated router.
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[Appendix B] B.8 Protocol Statements
Point-to-point interfaces have one additional parameter:
nomulticast
Forces gated to unicast OSPF packets over this interface. By default, OSPF packets to
neighbors on point-to-point interfaces are sent via the IP multicast mechanism. Use this
option if the remote neighbor does not support multicasting.
All interfaces - NBMA, point-to-point, and broadcast - can use these parameters:
enable | disable ;
Enables or disables the interface.
retransmitinterval time ;
Defines the number of seconds between link-state advertisement retransmissions.
transitdelay time ;
Defines the estimated number of seconds required to transmit a link-state update over
this interface. It must be greater than 0.
priority priority ;
Defines this system's priority for the designated router election. priority is a number
from 0 to 255. The router with the highest priority becomes the designated router. A
router whose priority is 0 is ineligible to become the designated router. See
Chapter 7
for a discussion of desginated routers.
hellointerval time ;
Defines the number of seconds between transmissions of HELLO packets.
routerdeadinterval time ;
Defines the timeout before a neighbor is declared down. time is the maximum number
of seconds this router will wait for a neighbor's Hello packet.
authkey key ;
Defines a key used to authenticate OSPF packets. The key is specified as one to eight
decimal digits separated by periods, a one- to eight-byte hexadecimal string preceded by
0x, or a one- to eight-character string in double quotes.

virtuallink neighborid router_id transitarea area
Defines a virtual link for the backbone area. The router_id is the router identifier of the
remote router at the other end of the virtual link. The transit area must be one of the other areas
configured on this system. All standard interface parameters defined above may be specified on
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