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na_routed - network RIP and router discovery routing daemon
routed [ -mopAtv ] [ -T tracefile ] [ -P parms ] [ on|off
]
routed [ -n ] status
Routed is a daemon invoked at boot time to manage the network
routing tables. It uses Routing Information Protocol,
RIPv1 (RFC 1058), RIPv2 (RFC 1723), and Internet
Router Discovery Protocol (RFC 1256) to maintain the kernel
routing table. The RIPv1 protocol is based on the
reference BSD 4.3 daemon.
It listens on the udp socket for the route service for
Routing Information Protocol packets. It also solicits
multicast Router Discovery ICMP messages.
When started (or when a network interface is later turned
on), routed uses an AF_ROUTE address family facility to
find those directly connected interfaces configured into
the system and marked "up". It adds necessary routes for
the interfaces to the kernel routing table. Soon after
being first started, and provided there is at least one
interface on which RIP has not been disabled, routed
deletes all pre-existing non-static routes in kernel
table. Static routes in the kernel table are preserved.
Normally routed acts as a silent router and never broadcasts
its routing table. This is similar to the -q option
on Unix systems. However, routed will respond to requests
from query programs such as rtquery by answering with the
complete table. In addition, the -m option, described
below, will cause RIP response messages to be generated.
The routing table maintained by the daemon includes space
for several gateways for each destination to speed recovery
from a failing router. RIP response packets received
are used to update the routing tables provided they are
from one of the several currently recognized gateways or
advertise a better metric than at least one of the existing
gateways.
When an update is applied, routed records the change in
its own tables and updates the kernel routing table if the
best route to the destination changes.
In addition to processing incoming packets, routed also
periodically checks the routing table entries. If an
entry has not been updated for 3 minutes, the entry's metric
is set to infinity and marked for deletion. Deletions
are delayed until the route has been advertised with an
infinite metric to insure the invalidation is propagated
throughout the local internet. This is a form of poison
reverse.
Routes in the kernel table that are added or changed as a
result of ICMP Redirect messages are deleted after a while
to minimize black-holes . When a TCP connection suffers a
timeout, the kernel tells routed, which deletes all redirected
routes through the gateway involved, advances the
age of all RIP routes through the gateway to allow an
alternate to be chosen, and advances of the age of any
relevant Router Discovery Protocol default routes.
If no response is received on a remote interface, or if
there are more errors than input or output (see na_netstat(1)),
then the cable or some other part of the interface
is assumed to be disconnected or broken, and routes
are adjusted appropriately.
The Internet Router Discovery Protocol is handled similarly.
If routed receives a good Advertisement and it is
not multi-homed, it stops listening for broadcast or multicast
RIP responses. It tracks several advertising
routers to speed recovery when the currently chosen router
dies. If all discovered routers disappear, the daemon
resumes listening to RIP responses. It continues listen
to RIP while using Router Discovery if multi-homed to
ensure all interfaces are used.
The Router Discovery standard requires that advertisements
have a default "lifetime" of 30 minutes. That means
should something happen, a client can be without a good
route for 30 minutes. It is a good idea to reduce the
default to 45 seconds using -P rdisc_interval=45 on the
command line or rdisc_interval=45 in the /etc/gateways
file.
While using Router Discovery (which happens by default
when the system has a single network interface and a
Router Discover Advertisement is received), there is a
single default route and a variable number of redirected
host routes in the kernel table. On a host with more than
one network interface, this default route will be via only
one of the interfaces. Thus, multi-homed hosts might need
no_rdisc described below.
See the pm_rdisc facility described below to support
"legacy" systems that can handle neither RIPv2 nor Router
Discovery.
By default, Router Discovery advertisements are not sent
over point to point links (e.g. PPP). The netmask associated
with point-to-point links (such as SLIP or PPP, with
the IFF_POINTOPOINT flag) is used by routed to infer the
netmask used by the remote system when RIPv1 is used.
The following options are available:
-
-m
- causes the machine to advertise a host or pointto-point
route to its primary interface. It is
useful on multi-homed machines such as NFS
servers. This option should not be used except
when the cost of the host routes it generates is
justified by the popularity of the server.
-
-A
- does not ignore RIPv2 authentication if we do
not care about RIPv2 authentication. This
option is required for conformance with RFC
1723. However, it makes no sense and breaks
using RIP as a discovery protocol to ignore all
RIPv2 packets that carry authentication when
this machine does not care about authentication.
-
-t
- increases the debugging level, which causes more
information to be logged on the tracefile specified
with -T or standard out. The debugging
level can be increased or decreased with the
rtquery command from a client.
-
-o
- turns off tracing by setting the debugging level
back to zero.
-
-T tracefile
-
increases the debugging level to at least 1 and
causes debugging information to be appended to
the trace file. Note that because of security
concerns, it is wisest to not run routed routinely
with tracing directed to a file.
-
-v
- displays and logs the version of daemon.
-
-P parms
- is equivalent to adding the parameter line parms
to the /etc/gateways file.
-
on
- turns on routed.
-
off
- turns off routed.
-
status
- This option is present for backwards compatibility
with the old routed. It prints out an indication
of whether routed is on or off and some
information about the default route. The format
of the output matches that of the old routed.
If the -n option is used, the default gateway is
printed out numerically. See na_orouted(1) for
information about the old routed. The output of
this option is likely to change in a future
release.
Routed also supports the notion of "distant" passive or
active gateways. When routed is started, it reads the
file /etc/gateways to find such distant gateways which may
not be located using only information from a routing
socket, to discover if some of the local gateways are pas_sive,
and to obtain other parameters. Gateways specified
in this manner should be marked passive if they are not
expected to exchange routing information, while gateways
marked active should be willing to exchange RIP packets.
Routes through passive gateways are installed in the kernel's
routing tables once upon startup and are not
included in transmitted RIP responses.
Distant active gateways are treated like network interfaces.
RIP responses are sent to the distant active gateway.
If no responses are received, the associated route
is deleted from the kernel table and RIP responses advertised
via other interfaces. If the distant gateway
resumes sending RIP responses, the associated route is
restored.
Such gateways can be useful on media that do not support
broadcasts or multicasts but otherwise act like classic
shared media like Ethernets such as some ATM networks.
One can list all RIP routers reachable on the ATM network
in /etc/gateways with a series of "host" lines. Note that
it is usually desirable to use RIPv2 in such situations to
avoid generating lists of inferred host routes.
Gateways marked external are also passive, but are not
placed in the kernel routing table nor are they included
in routing updates. The function of external entries is
to indicate that another routing process will install such
a route if necessary, and that other routes to that destination
should not be installed by routed. Such entries
are only required when both routers may learn of routes to
the same destination.
The /etc/gateways file comprises a series of lines, each
in one of the following two formats or consists of parameters
described later. Blank lines and lines starting with
`#' are comments.
net <Nname[/mask]> gateway <Gname> metric <value> < pas_sive
No | active No | extern >
host <Hname> gateway <Gname> metric <value> < passive No
active No | extern >
<Nname> or <Hname> is the name of the destination network
or host. It may be a symbolic network name or an Internet
address specified in "dot" notation. (If it is a name,
then it must either be defined in /etc/networks or
/etc/hosts , or DNS and/or NIS, must have been started
before routed.)
<Mask> is an optional number between 1 and 32 indicating
the netmask associated with <Nname>.
<Gname> is the name or address of the gateway to which RIP
responses should be forwarded.
<Value> is the hop count to the destination host or network.
" host hname " is equivalent to " net nname/32 ".
One of the keywords passive, active or external must be
present to indicate whether the gateway should be treated
as passive or active (as described above), or whether the
gateway is external to the scope of the RIP protocol.
As can be seen when debugging is turned on with -t , such
lines create psuedo-interfaces. To set parameters for
remote or external interfaces, a line starting with
if=alias(Hname) , if=remote(Hname) , etc. should be used.
Lines that start with neither "net" nor "host" must consist
of one or more of the following parameter settings,
separated by commas or blanks:
if = <ifname>
indicates that the other parameters on the line
apply to the interface name <ifname>.
subnet = <nname[/mask][,metric]>
advertises a route to network <nname> with mask
<mask> and the supplied metric (default 1).
This is useful for filling "holes" in CIDR allocations.
This parameter must appear by itself
on a line. The network number must specify a
full, 32-bit value, as in 192.0.2.0 instead of
192.0.2.
Do not use this feature unless necessary. It is dangerous.
ripv1_mask = <nname/mask1,mask2>
specifies that netmask of the network of which
nname/mask1 is a subnet should be mask2 . For
example ripv1_mask=192.0.2.16/28,27 marks
192.0.2.16/28 as a subnet of 192.0.2.0/27
instead of 192.0.2.0/24.
passwd = <XXX[|KeyID[start|stop]]>
specifies a RIPv2 cleartext password that will
be included on all RIPv2 responses sent, and
checked on all RIPv2 responses received. Any
blanks, tab characters, commas, or `#', `|', or
NULL characters in the password must be escaped
with a backslash (\). The common escape
sequences \n, \r, \t, \b, and \xxx have their
usual meanings. The KeyID must be unique but is
ignored for cleartext passwords. If present,
start and stop are timestamps in the form
year/month/day@hour:minute. They specify when
the password is valid. The valid password with
the most future is used on output packets,
unless all passwords have expired, in which case
the password that expired most recently is used,
or unless no passwords are valid yet, in which
case no password is output. Incoming packets
can carry any password that is valid, will be
valid within 24 hours, or that was valid within
24 hours. To protect the secrets, the passwd
settings are valid only in the /etc/gateways
file and only when that file is readable only by
UID 0.
md5_passwd = <XXX|KeyID[start|stop]>
specifies a RIPv2 MD5 password. Except that a
KeyID is required, this keyword is similar to
passwd .
-
no_ag
- turns off aggregation of subnets in RIPv1 and
RIPv2 responses.
no_super_ag
turns off aggregation of networks into supernets
in RIPv2 responses.
passive marks the interface to not be advertised in
updates sent via other interfaces, and turns off
all RIP and router discovery through the interface.
-
no_rip
- disables all RIP processing on the specified
interface. If no interfaces are allowed to process
RIP packets, routed acts purely as a router
discovery daemon.
Note that turning off RIP without explicitly turning on
router discovery advertisements with rdisc_adv causes
routed to act as a client router discovery daemon, not
advertising.
no_rip_mcast
causes RIPv2 packets to be broadcast instead of
multicast.
no_ripv1_in
causes RIPv1 received responses to be ignored.
no_ripv2_in
causes RIPv2 received responses to be ignored.
ripv2_out turns off RIPv1 output and causes RIPv2 advertisements
to be multicast when possible.
-
ripv2
- is equivalent to no_ripv1_in and no_ripv1_out .
no_rdisc disables the Internet Router Discovery Protocol.
no_solicit
disables the transmission of Router Discovery
Solicitations.
send_solicit
specifies that Router Discovery solicitations
should be sent, even on point-to-point links,
which by default only listen to Router Discovery
messages.
no_rdisc_adv
disables the transmission of Router Discovery
Advertisements.
rdisc_adv specifies that Router Discovery Advertisements
should be sent, even on point-to-point links,
which by default only listen to Router Discovery
messages.
bcast_rdisc
specifies that Router Discovery packets should
be broadcast instead of multicast.
rdisc_pref = <N>
sets the preference in Router Discovery Advertisements
to the optionally signed integer <N>.
The default preference is 0. Default routes
with smaller or more negative preferences are
preferred by clients.
rdisc_interval = <N>
sets the nominal interval with which Router Discovery
Advertisements are transmitted to N seconds
and their lifetime to 3*N.
fake_default = <metric>
has an identical effect to -F <net[/mask][=metric]>
with the network and mask coming from the
specified interface.
pm_rdisc is similar to fake_default . When RIPv2 routes
are multicast, so that RIPv1 listeners cannot
receive them, this feature causes a RIPv1
default route to be broadcast to RIPv1 listeners.
Unless modified with fake_default , the
default route is broadcast with a metric of 14.
That serves as a "poor man's router discovery"
protocol.
trust_gateway = <rname[|net1/mask1|net2/mask2|...]>
causes RIP packets from that router and other
routers named in other trust_gateway keywords to
be accepted, and packets from other routers to
be ignored. If networks are specified, then
routes to other networks will be ignored from
that router.
/etc/gateways for distant gateways
na_netstat(1), na_route(1), na_setup(1), na_dgateways(5),
na_rc(5)
It does not always detect unidirectional failures in network
interfaces, for example, when the output side fails.
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