ROUTING and GATEWAY
Gateway: Gateway
is a network point that acts as an entrance to another network. A gateway is
required to convert Data packets from one protocol format to another Protocol format,
as it connects two dissimilar networks.
Router:
A router is connected to two different networks and passes
packets between them. Router and Gateway both are sometimes used
interchangeably but the difference is that Gateway operates on 7th layer of the
OSI Model and the Router works on the 3rd layer of the OSI model.
Here we will
describe some routing configuration on different platforms.
Linux Red Hat
1.
To
view the current routing table run “route
-n”
[root@cdacqmail ~]# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric
Ref
Use Iface
169.254.95.0 0.0.0.0
255.255.255.0 U 1 0
0 usb0
220.156.188.0 0.0.0.0
255.255.254.0 U 0 0
0 eth1
169.254.0.0 0.0.0.0
255.255.0.0 U 1002
0
0 eth0
169.254.0.0 0.0.0.0
255.255.0.0 U 1003 0
0 eth1
10.0.0.0 0.0.0.0
255.0.0.0 U 0 0
0 eth0
0.0.0.0 220.156.188.145 0.0.0.0 UG 0 0 0 eth1
2. Adding a Default Gateway
route add default
gw 220.156.188.145
3.
To
add a route refers to the command below.
route add
-net 10.226.16.0 netmask 255.255.240.0 gw 10.226.0.201
4.
To
delete a route refer to the command below.
route del
-net 10.226.16.0 netmask 255.255.240.0 gw 10.226.0.201
The routing
information above is not persistent across reboots. After a reboot, the routing
information will be lost and you need to add them in again.
5.
To
make the routing information persistent, add the “route add” line as
seen above into the /etc/rc.local
file.
Sample
/etc/rc.local
file.
#!/bin/sh
#
# This
script will be executed *after* all the other init scripts.
# You can
put your own initialization stuff in here if you don't
# want to
do the full Sys V style init stuff.
touch /var/lock/subsys/local
route add
-net 10.226.16.0 netmask 255.255.240.0 gw 10.226.0.201
6. Reject Routing to a Particular Host or Network
route add -host 192.168.1.51
reject
7.
If
you want to reject an entire network (192.168.1.1 – 192.168.1.255), then add
the following entry.
route add -net 192.168.1.0 netmask
255.255.255.0 reject
UBUNTU
1. Adding
Route
route
add -net $NET netmask $MASK gw $GATEWAY
route
add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254
You need to
add above syntax to post-up command as follows:
post-up command
post-up route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254
Given
command will run after bringing the interface up.
Example
Edit /etc/network/interfaces, enter:
$ sudo vi /etc/network/interfaces
#---------------------------------------#
# Feel free to change IP and gateway #
# as per your local setup and routing #
# policy #
# Last edited by root @ 23/Oct/2012 #
#---------------------------------------#
#--------------------------------------------#
# Setup the loopback network interface (lo0) #
#--------------------------------------------#
auto lo
iface lo inet loopback
#--------------------------------------------#
# Setup eth0 - connected to private LAN/VLAN #
#--------------------------------------------#
auto eth0
allow-hotplug eth0
iface eth0 inet static
address 10.70.201.5
netmask 255.255.255.192
### Ubuntu Linux add persistent route command ###
post-up route add -net 10.0.0.0 netmask 255.0.0.0 gw 10.70.201.6
#----------------------------------------#
# Setup eth1 - connected to the Internet #
#----------------------------------------#
auto eth1
allow-hotplug eth1
iface eth1 inet static
address 205.153.203.98
netmask 255.255.255.248
### Ubuntu Linux - This is your default gateway ###
gateway 205.153.203.97
Save and
close the file.
2. You need to restart the networking as follows:
$ sudo
service networking restart
OR as root user:
#
service networking restartWINDOWS Server1. You can check routing
in windows by following step:C:\Documents
and Settings\jitendrakumar>route printIPv4
Route Table===========================================================================Interface
List0x1
........................... MS TCP Loopback interface0x20003
...00 23 ae 77 ee 57 ...... Broadcom NetLink (TM) Gigabit Ethernet======================================================================================================================================================Active
Routes:Network
Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 10.226.0.201 10.226.1.206 10 10.0.0.0 255.255.240.0 10.0.0.206 10.226.1.206 10 10.0.0.206 255.255.255.255 127.0.0.1 127.0.0.1 10 10.226.0.0 255.255.240.0 10.226.1.206 10.226.1.206 10 10.226.1.206 255.255.255.255 127.0.0.1 127.0.0.1 10 10.255.255.255 255.255.255.255 10.226.1.206 10.226.1.206 10 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 172.20.0.0 255.255.254.0 172.20.0.206 10.226.1.206 10 172.20.0.0 255.255.0.0 172.20.0.1 10.226.1.206 1 172.20.0.206 255.255.255.255 127.0.0.1 127.0.0.1 10 172.20.255.255 255.255.255.255 10.226.1.206 10.226.1.206 10 224.0.0.0 240.0.0.0 10.226.1.206 10.226.1.206 10 255.255.255.255 255.255.255.255 10.226.1.206 10.226.1.206 1Default
Gateway: 10.226.0.201===========================================================================Persistent
Routes: Network Address Netmask Gateway Address Metric172.20.0.0
255.255.0.0 172.20.0.1 1
2. Adding Route in
Window server
route add
<destination> mask <subnet mask> <gateway> metric <lowest
number wins> if <interface>
Ex-
route ADD 157.0.0.0 MASK 155.0.0.0 157.55.80.1 METRIC 2 IF
2
3.
Deleting route in windows server
route delete 157.0.0.0 MASK 155.0.0.0
157.55.80.1 METRIC
2 IF 2
4. Adding Persistent Route.
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
route \[-p\] add <destination> mask <subnet mask>
<gateway> metric <lowest number wins> if <interface>
metric Metric : Specifies
an integer cost metric (ranging from 1 to 9999) for the route, which is used
when choosing among multiple routes in the routing table that most closely
match the destination address of a packet being forwarded. The route with the
lowest metric is chosen. The metric can reflect the number of hops, the speed
of the path, path reliability, path throughput, or administrative properties.
if Interface : Specifies
the interface index for the interface over which the destination is reachable.
For a list of interfaces and their corresponding interface indexes, use the
display of the route print command. You can use either decimal or
hexadecimal values for the interface index. For hexadecimal values, precede the
hexadecimal number with0x. When the if parameter is omitted, the interface is
determined from the gateway address.
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