Summarization &
Summary routes
ASSIGNMENT
a method where we create one summary route that represent
multiple networks/subnets
By : Hajer Ghinnewa & Elias Elmaghabob
Hajer : 181012
Elias : 182244
introduction
Pg. 01
Strategic Highlights
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Hajer Ghinnewa
Elias Elmaghbob
January 10, 2022
introduction
Pg. 02
Introduction
A route advertisement contains information that devices can use to
communicate across an IP network.
Route summarization advertises a bunch of contiguous routes from
the routing table in the form of a single summarized or aggregated
route ,here we explain how it is work and What are the advantages
and disadvantages of using it.
introduction
Pg. 03
Route summarization:
Or supernetting, is needed to reduce the number of routes that a router advertises to its
neighbor.
when a new data flow enters a router, the router must do a lookup in its routing table to
determine which interface the traffic must be sent out. The larger the routing tables, the longer
this takes, leading to more used router CPU cycles to perform the lookup.
Route summarization also known as route aggregation
With route summarization, many routes are advertised with just one line in an update packet,
which not only reduces the packet size, but also allows more bandwidth for data transfer.
The advantages of Summarization:
•
Saves CPU cycles : less packets to process and smaller routing tables to work on.
•
Stability: Prevents routing table instability due to flapping networks.
•
Saves memory: routing tables will be smaller which reduces memory requirements.
•
Saves bandwidth: there are less routes to advertise so we save some bandwidth.
The disadvantages of Summarization:

Forwarding traffic for unused networks: a router will drop traffic when it doesn’t have a
matching destination in its routing table. When we use summarization, it’s possible that
the summary route covers networks that are not in use. The router that has a summary
route will forward them to the router that has advertised the summary route.

Sub-optimal routing: routers prefer the path with the longest prefix match. When you
use summaries, it’s possible that your router prefers another path where it has learned
a more specific network from. The summary route also has a single metric.
Example topology:
introduction
Pg. 04
Ip
Revenue
172.16.00000000.00000001
255.255.255.0
172.16.00000001.00000001
255.255.255.0
172.16.00000010.00000001
255.255.255.0
172.16.00000011.00000001
255.255.255.0
Result : 172.16.0.0/22
Example topology:
172.16.64.0 = 10101100.00010000.01000000.00000000
172.16.65.0 = 10101100.00010000.01000001.00000000
172.16.66.0 = 10101100.00010000.01000010.00000000
172.16.67.0 = 10101100.00010000.01000011.00000000
Common bits: 10101100.00010000.010000xx
Result : 172.16.64.0/22