The IP routing table

Every computer that runs TCP/IP makes routing decisions. These decisions are controlled by the IP routing table. To display the IP routing table on computers running Windows Server 2008R2 operating systems, you can type route print at a command prompt.

The following table shows an example of an IP routing table for a network adapter with the following configuration:

• IP address: 10.0.0.169
  
• Subnet mask: 255.0.0.0
  
• Default gateway: 10.0.0.1

The routing table is built automatically, based on the current TCP/IP configuration of your computer. Each route occupies a single line in the displayed table. Your computer searches the routing table for an entry that most closely matches the destination IP address.

The following sections describe each of the columns displayed in the IP routing table: network destination, netmask, gateway, interface, and metric.

• Network destination: The network destination is used with the netmask to match the destination IP address. The network destination can range from 0.0.0.0 for the default route through 255.255.255.255 for the limited broadcast, which is a special broadcast address to all hosts on the same network segment. 
• Netmask: The netmask is the subnet mask that is applied to the destination IP address when matching it to the value in the network destination.
• Gateway: The gateway address is the IP address that the local host uses to forward IP datagrams to other IP networks. This is either the IP address of a local network adapter or the IP address of an IP router (such as a default gateway router) on the local network segment. 
• Interface: The interface is the IP address that is configured on the local computer for the local network adapter that is used when an IP datagram is forwarded on the network. 
• Metric: A metric indicates the cost of using a route, which is typically the number of hops to the IP destination. Anything on the local subnet is one hop, and each router crossed after that is an additional hop. If there are multiple routes to the same destination with different metrics, the route with the lowest metric is selected.

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