The Geek Diary

How to Display Routing Table in Linux

by

To display the kernel routing table, you can use any of the following methods:

route

List all the current static routes:

$ sudo route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         192.168.0.1     0.0.0.0         UG    0      0        0 eth0

You need to be root to execute route. The -n option means that you want numerical IP addresses displayed, instead of the corresponding host names.

netstat

netstat is another easy command that can be used to display the static routes.

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.0.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
0.0.0.0         192.168.0.1     0.0.0.0         UG        0 0          0 eth0

The -r option specifies that you want the routing table. The -n option is similar to that of the route command.

ip

ip command can be used to display IPv4 as well as IPv6 routing tables. The below command displays the IPv4 routing table.

$ ip route list
192.168.0.0/24 dev eth0  proto kernel  scope link  src 192.168.0.103
default via 192.168.0.1 dev eth0
$ ip route
default via 10.0.2.2 dev eth0 proto dhcp metric 100 
10.0.2.0/24 dev eth0 proto kernel scope link src 10.0.2.15 metric 100 
172.16.0.0/12 via 192.168.33.11 dev eth1 
192.168.33.0/24 dev eth1 proto kernel scope link src 192.168.33.10 metric 101

How to view IPv6 routes

To view IPv6 routing table, use the command:

# ip -6 route
Note: The route command from the net-tools package is considered deprecated and should be avoided in favor of the iproute tools such as ip.

For more information on ip command, see the man page:

# man ip

Final Notes

When the route -n command is issued, there is an address listed of “0.0.0.0”. This entry in the route table indicates the route to the Default Gateway. As an outgoing packet is created, the destination address is assigned. The kernel will examine the current routing table from top to bottom. If no matches are found for the destination address the packet will be sent through the default gateway. The address seen of 0.0.0.0 indicates a match for everything. The four 0’s act as wildcards in an IP address.

For example, given the routing table below, any packet not destined for the 192.168.122.0/24 network will be sent to the default gateway of 192.168.122.1 through the eth0 interface:

# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.122.0   0.0.0.0         255.255.255.0   U     1      0        0 eth0
0.0.0.0         192.168.122.1   0.0.0.0         UG    0      0        0 eth0

You May Also Like