NAME
route
—
manually manipulate the routing
tables
SYNOPSIS
route |
[-dnqtv ] [-T
rtable] command
[[modifiers] args] |
DESCRIPTION
route
is a utility used to manually view
and manipulate the network routing tables. route
can
be used to modify nearly any aspect of the routing policy, except packet
forwarding, which can be manipulated through the
sysctl(8) command.
The route
utility supports a limited
number of general options, but a rich command language enables the user to
specify any arbitrary request that could be delivered via the programmatic
interface discussed in
route(4).
The options are as follows:
-d
- Run in debug-only mode, i.e., don't actually modify the routing table.
-n
- Bypass attempts to print host and network names symbolically when reporting actions. (The process of translating between symbolic names and numerical equivalents can be quite time consuming, and may require correct operation of the network; thus it may be expedient to forgo this, especially when attempting to repair networking operations.)
-q
- Suppress all output.
-T
rtable- Select an alternate routing table to modify or query. The default is to use the current routing table.
-t
- Write routing messages to a fake device (/dev/null) instead of a real routing socket to test route manipulation.
-v
- (verbose) Print additional details.
The route
utility provides the following
simple commands:
route
[-T
rtable]exec
[command ...]- Execute a command forcing the process and its children to use the routing
table and appropriate routing domain as specified with the
-T
rtable option. route
[-nqv
] [-T
rtable]flush
[modifiers]- Delete all gateway entries from the routing table. When the address family
is specified by any one of the family modifiers
(listed below), only routes having destinations with addresses in the
delineated family will be deleted. Also, only routes matching a specific
interface or priority can be flushed by using the
-iface
or-priority
modifiers. route
[-nv
] [-T
rtable]get
[modifiers] address- Extract a routing entry from the kernel. If
-gateway
is specified, only routes whose gateway are in the same address family as the destination are shown. route
[-n
] [-T
rtable]monitor
[modifiers]- Continuously report any changes to the routing information base, routing
lookup misses, or suspected network partitionings.
When the address family is specified by any one of the family modifiers (listed below), only routes having destinations with addresses in the delineated family will be shown. If the
-iface
modifier is used only interface specific messages (link state changes) are shown. If a routing table is supplied with-T
, only changes in that routing table will be displayed. route
[-nv
] [-T
rtable]show
[family] [-gateway
] [-label
label] [-priority
priority]- Print out the routing table, in a fashion similar to "netstat
-r". The output is documented in more detail towards the end of the
netstat(1) manual.
If
-gateway
is specified, only routes whose gateway are in the same address family as the destination are shown.If
-label
is specified, only routes with the specified label are shown.If
-priority
is specified, only routes with the specified priority are shown. It may be specified by number or one oflocal
,connected
,static
,ospf
,rip
, orbgp
. If the priority is negative, then routes that do not match the numeric priority are shown.
The other commands relating to adding, changing, or deleting routes have the syntax:
route
[-dnqtv
] [-T
rtable]add
[modifiers] destination gatewayroute
[-dnqtv
] [-T
rtable]change
[modifiers] destination gatewayroute
[-dnqtv
] [-T
rtable]del
[ete
] [modifiers] destination gateway
destination is the destination host or
network; gateway is the next-hop intermediary via
which packets should be routed. Routes to a particular host may be
distinguished from those to a network by interpreting the Internet address
specified as the destination argument. The optional
modifiers -net
and -host
cause the destination to be interpreted as a network or a host,
respectively. Otherwise, type is chosen based on the following rules:
The route is assumed to be to a network if any of the following apply to destination:
- it is the word "default", equivalent to 0/0
- it is an IPv4 address with less than 3 dots
- it is an IPv4 address with a “/XX” suffix (where XX is the number of bits in the network portion of the address and is less than 32)
- it is an IPv6 address with a “/XX” suffix (where XX is the number of bits in the network portion of the address and is less than 128)
- it is the symbolic name of a network.
If destination is a valid IP address or host name, it is presumed to be a route to a host.
For example, 192.168.1.1
is interpreted as
-host
192.168.1.1
and
192.168.1
is interpreted as
-net
192.168.1
. Note,
however, that 192.168.2.0
will be interpreted as
-host
192.168.2.0
since it
is a complete IP address with 3 dots. In this case the number of bits in the
network portion of the address must be explicitly listed, for example
192.168.2.0/24
,
192.168.2/24
, or alternately
192.168.2
.
If the destination is directly reachable via an interface
requiring no intermediary system to act as a gateway, the
-iface
modifier should be specified; the gateway
given is the address of this host on the common network, indicating the
interface to be used for transmission.
To allow addresses to be interpreted as belonging to a particular address family (as well as for use in the family arguments to some commands), the following modifiers may be used:
-inet
- Internet Protocol version 4 (IPv4) addresses (see ip(4))
-inet6
- Internet Protocol version 6 (IPv6) addresses (see ip6(4))
-link
- Hardware (link-level) addresses
-mpls
- MPLS addresses
-sa
- Actual sockaddr data, in hexadecimal format
In the absence of modifiers, an address is assumed to be IPv4, unless containing a ‘:’ character, when it is treated as IPv6.
The optional modifier -link
specifies that
all subsequent addresses are specified as link-level addresses, and the
names must be numeric specifications rather than symbolic names.
The optional -netmask
qualifier is
intended to manually add subnet routes with netmasks different from that of
the implied network interface (as would otherwise be communicated using a
routing protocol). One specifies an additional ensuing address parameter (to
be interpreted as a network mask). The implicit network mask generated in
the AF_INET
case can be overridden by making sure
this option follows the destination parameter.
-prefixlen
is also available for a similar purpose,
for IPv6/v4.
A specific routing priority can be specified with the optional
-priority
qualifier. If no priority is specified the
kernel will set a priority depending on the RTF_STATIC flag to either
RTP_STATIC or RTP_DEFAULT. Note that priority 1 is reserved for kernel
use.
The optional -mpath
modifier needs to be
specified with the add
command to be able to enter
multiple gateways for the same destination address (multipath). When
multiple routes exist for a destination, one route is selected based on the
source address of the packet. The
sysctl(8) variables net.inet.ip.multipath and
net.inet6.ip6.multipath are used to control multipath
routing. If set to 1, multiple routes with the same priority are used
equally; if set to 0, the first route selected will be used for subsequent
packets to that destination regardless of source.
When inserting MPLS routes, particular modifiers must be used. The
-mplslabel
modifier needs to be specified in an
ingress LSR to associate a particular label to an IPv4/IPv6 route. The MPLS
traffic -in
and -out
modifiers are intended to identify the ingress label and, optionally, the
outgoing one. Additionally, one of the following operations must be used:
-push
, -pop
and
-swap
. Route's nexthop can be specified with the
modifier -inet
.
Routes have associated flags which influence operation of the protocols when sending to destinations matched by the routes. These flags may be set (or sometimes cleared) by indicating the following corresponding modifiers:
-blackhole |
RTF_BLACKHOLE |
silently discard pkts (during updates) |
-cloning |
RTF_CLONING |
generates a new route on use |
-iface |
~RTF_GATEWAY |
destination is directly reachable |
-llinfo |
RTF_LLINFO |
validly translates proto addr to link addr |
-mpath |
RTF_MPATH |
multiple gateways for a destination exist |
-nostatic |
~RTF_STATIC |
pretend route added by kernel or daemon |
-proto1 |
RTF_PROTO1 |
set protocol specific routing flag #1 |
-proto2 |
RTF_PROTO2 |
set protocol specific routing flag #2 |
-reject |
RTF_REJECT |
emit an ICMP unreachable when matched |
-static |
RTF_STATIC |
manually added route |
The optional modifiers -expire
and
-mtu
provide initial values to quantities maintained
in the routing entry by transport level protocols, such as TCP (see
tcp(4)). They have the following meanings:
-expire
n- Lifetime for route (e.g., if generated by a redirect).
-mtu
n- Maximum transmission unit (MTU) size for this path.
These may be individually locked by preceding each such modifier
to be locked by the -lock
meta-modifier, or one can
specify that all ensuing metrics may be locked by the
-lockrest
meta-modifier.
In a change
or add
command where the destination and gateway are not sufficient to specify the
route, the -ifp
or -ifa
modifiers may be used to determine the interface name or interface
address.
The optional -label
modifier
specifies on route addition or modification that the route should have the
given label
associated with it. Route labels can be used to attach arbitrary information
to a route.
All symbolic names specified for a destination or gateway are looked up using gethostbyname(3).
route
uses a routing socket (see
route(4)) and the message types RTM_ADD
,
RTM_DELETE
, RTM_GET
, and
RTM_CHANGE
. As such, only the superuser may modify
the routing tables.
FILES
- /etc/hosts
- host and network name database
- /etc/mygate
- default gateway address
EXAMPLES
Add a static inet(4) route to the 192.168.5.0/24 network via the 192.168.0.1 gateway:
# route add -inet 192.168.5.0/24
192.168.0.1
Amend the inet(4) route to the 192.168.5.0/24 network to use the 192.168.0.2 gateway:
# route change -inet 192.168.5.0/24
192.168.0.2
Delete the inet(4) route to the 192.168.5.0/24 network:
# route delete -inet
192.168.5.0/24
DIAGNOSTICS
- %s: gateway %s flags %x
- The specified route is being added to or deleted from the tables. If the gateway address used was not the primary address of the gateway (the first one returned by gethostbyname(3)), the gateway address is printed numerically as well as symbolically.
- %s %s done
- When the
flush
command is specified, each routing table entry deleted is indicated with a message of this form. - Network is unreachable
- An attempt to add a route failed because the gateway listed was not on a directly connected network. The next-hop gateway must be given.
- not in table
- A
delete
operation was attempted for an entry which wasn't present in the tables. - routing table overflow
- An
add
operation was attempted, but the system was low on resources and was unable to allocate memory to create the new entry.
SEE ALSO
netstat(1), gethostbyname(3), netintro(4), route(4), tcp(4), hosts(5), mygate(5), bgpd(8), ospfd(8), ripd(8), sysctl(8)
HISTORY
The route
command appeared in
4.2BSD. IPv6 support was added by WIDE/KAME
project.
The -recvpipe
,
-hopcount
, -sendpipe
,
-ssthres
, -rtt
, and
-rttvar
modifiers used to be used to initialize
various quantities in routing table entries. The routing system no longer
uses these values and the modifiers exist now only for compatibility with
other operating systems.
BUGS
Some uses of the -ifa
or
-ifp
modifiers with the add
command will incorrectly fail with a “Network is unreachable”
message if there is no default route. See case
RTM_ADD
in route_output
()
from sys/net/rtsock.c for details.