Usages of Route Commands

Dos route command
——————-
Command to manually configure the routes in the routing table

Syntax

ROUTE [-f] [-p] [-4|-6] command [destination]
[MASK netmask] [gateway] [METRIC metric] [IF interface]

-f Clears the routing tables of all gateway entries. If this is
used in conjunction with one of the commands, the tables are
cleared prior to running the command.

-p When used with the ADD command, makes a route persistent across
boots of the system. By default, routes are not preserved
when the system is restarted. Ignored for all other commands,
which always affect the appropriate persistent routes.This
option is not supported in Windows 95.

-4 Force using IPv4.

-6 Force using IPv6.

command One of these:
PRINT Prints a route
ADD Adds a route
DELETE Deletes a route
CHANGE Modifies an existing route
destination Specifies the host.
MASK Specifies that the next parameter is the ‘netmask’ value.
netmask Specifies a subnet mask value for this route entry.
If not specified, it defaults to 255.255.255.255.
gateway Specifies gateway.
interface the interface number for the specified route.
METRIC specifies the metric, ie. cost for the destination.

All symbolic names used for destination are looked up in the network database
file NETWORKS. The symbolic names for gateway are looked up in the host name
database file HOSTS.

If the command is PRINT or DELETE. Destination or gateway can be a wildcard,
(wildcard is specified as a star ‘*’), or the gateway argument may be omitted.

If Dest contains a * or ?, it is treated as a shell pattern, and only
matching destination routes are printed. The ‘*’ matches any string,
and ‘?’ matches any one char. Examples: 157.*.1, 157.*, 127.*, *224*.

Pattern match is only allowed in PRINT command.
Diagnostic Notes:
Invalid MASK generates an error, that is when (DEST & MASK) != DEST.
Example> route ADD 157.0.0.0 MASK 155.0.0.0 157.55.80.1 IF 1
The route addition failed: The specified mask parameter is invalid.
(Destination & Mask) != Destination.

Examples:

> route PRINT
> route PRINT -4
> route PRINT -6
> route PRINT 157* …. Only prints those matching 157*

> route ADD 157.0.0.0 MASK 255.0.0.0 157.55.80.1 METRIC 3 IF 2
destination^ ^mask ^gateway metric^ ^
Interface^
If IF is not given, it tries to find the best interface for a given
gateway.
> route ADD 3ffe::/32 3ffe::1

> route CHANGE 157.0.0.0 MASK 255.0.0.0 157.55.80.5 METRIC 2 IF 2

CHANGE is used to modify gateway and/or metric only.

> route DELETE 157.0.0.0
> route DELETE 3ffe::/32

Command Purpose
add Adds a route.
change Modifies an existing route.
delete Deletes a route or routes.
print Prints a route or routes.

Route add

route add “destination” mask “subnetmask” “gateway” metric “costmetric” if
“interface”

Eg.
route add -p 10.0.0.0 mask 255.0.0.0 192.168.0.1 metric 2

In simple route add -p 10.0.0.0 mask 255.0.0.0 192.168.0.1

Routes added by using the -p option are stored in the Windows registry under the
following key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip \Parameters
\PersistentRoutes

To delete the route to the destination 10.41.0.0 with the subnet mask of
255.255.0.0, type:

route delete 10.41.0.0 mask 255.255.0.0

To delete all routes in the IP routing table that begin with 10., type:

route delete 10.*

To change the next hop address of the route with the destination of 10.41.0.0 and
the subnet mask of 255.255.0.0 from 10.27.0.1 to 10.27.0.25, type:

route change 10.41.0.0 mask 255.255.0.0 10.27.0.25

Linux route command
——————–
Display Existing Routes
$ route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0

$ route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 192.168.1.10 0.0.0.0 UG 0 0 0 eth0

Adding a Default Gateway
$ route add default gw 192.168.1.10

List Kernel’s Routing Cache Information
$ route -Cn
Kernel IP routing cache
Source Destination Gateway Flags Metric Ref Use Iface
192.168.1.157 192.168.1.51 192.168.1.51 0 0 1 eth0
192.168.1.157 74.125.236.69 192.168.1.10 0 0 0 eth0

Reject Routing to a Particular Host or Network
$ route add -host 192.168.1.51 reject
$ route add -net 192.168.1.0 netmask 255.255.255.0 reject

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