Route Sumarization

[The_guroo_2]

i m confused abt route sumarization....i know what it is but how we calculate it when we have amny routes whats the trick of that......thanks and possibblly give me example thanks a in advance

[pkhatri]

Route summarisation is used in order to reduce the number of routes that a router has to carry. The benefits of summarisation are:

- reduced memory requirements

- reduced bandwidth requirements since there are less routes to carry in routing updates

An example follows:

RtrA --- RtrB

Say router A has 4 routes it wants to advertise to RtrB:

10.1.0.0/24

10.1.1.0/24

10.1.2.0/24

10.1.3.0/24

IT could announce all four of these routes or it could summarise the 4 routes into 10.1.0.0/22. In terms of routing, it makes absolutely no difference whether you advertise the 4 routes separately or whether you advertise the single summary. But the single summary provides the advantages I've listed above.

Hope that helps - pls rate the post if it does.

Paresh

[Roberto Salazar]

Previous post is calculated as such, I will just show the third octet for simplicity:

10.1.0.0/24 = 0 0 0 0 0 0 0 0

10.1.1.0/24 = 0 0 0 0 0 0 0 1

10.1.2.0/24 = 0 0 0 0 0 0 1 0

10.1.3.0/24 = 0 0 0 0 0 0 1 1

So, with the above all of the subnets have in common on the 6 most significant bits hence the mask /22

I hope that helps and did not confused it even more.

[ashish-rohilla]

Right, Paresh explained well. But there is one disadvantage of using route summarization.

When full routes are not sent to remote device then remote device dont have full information abt each and every route. In such a case chances of routing loops are there. One advantage other than Paresh mentioned is if there is any link fluctuation or any route failure then this will not be floated beyond the router where route summarization is enabled.

Regards

[bhedlund]

A huge benefit with route summarization in a large EIGRP network is that it reduces wide spread EIGRP query activity by establishing query boundries. This reduces EIGRP network activity, improves convergence times, and helps prevent SIA (stuck in active) conditions.

Please rate all helpful posts.

-Brad