Manual Route Summarization

Manual route summarization is the process of creating a summary route for a group of contiguous subnets. This allows a router to advertise a single summary route instead of advertising all of the individual subnets, which can reduce the size of the routing table and improve routing efficiency.

Route summarization is typically used in networks that have a hierarchical design, where routers are organized into groups based on their location or function. In such networks, summarization can be used to simplify the routing tables and reduce the amount of traffic that needs to be routed.

To manually summarize routes, we need to identify the contiguous subnets that we want to summarize, and then determine the summary route that encompasses all of these subnets. The summary route will have a network address and a subnet mask that represents the range of the subnets being summarized.

Here is an example of how to manually summarize routes:

Suppose we have the following four subnets:

192.168.1.0/24

192.168.2.0/24

192.168.3.0/24

192.168.4.0/24

We can manually summarize these subnets into a single summary route with the network address 192.168.0.0 and a subnet mask of 255.255.252.0. This summary route encompasses all of the subnets from 192.168.1.0 to 192.168.4.0.

To configure manual route summarization on a router, we can use the following command:

ip route <summary-address> <subnet-mask> <next-hop>

For example, to configure the summary route for the above subnets on a Cisco router, we would use the following commands:

ip route 192.168.0.0 255.255.252.0 <next-hop> This creates a single summary route for all of the subnets, which can be advertised to other routers using a routing protocol such as OSPF or BGP.