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Configuring Classless EIGRP | disable auto summary eigrp

Configuring Classless EIGRP | disable auto summary eigrp

Asalam o alikum , Brothers & Sisters . Today we will learn Configuring classless EIGRP OR Disabling auto summary in EIGRP.

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. 

In old versions of Cisco IOS , auto-summarization was enabled by default while configuring EIGRP. This features summarizes any IP Addresses to classful networks automatically. EIGRP will check if you have any subnets that fall within the range of your network command(s) and if so, it will advertise the classful A, B or C network to its neighbors.

“In new releases of IOS , auto summary is disabled by default”

So if we have a class C IP subnet which is further divided into 4 /29 subnets , EIGRP Will advertise them as example:

All subnets shown above will be advertised as . To counter this , we will disable the auto-summarization in EIGRP using the command ” no auto-summary”.

After this configuration EIGRP will not advertise them as classful networks, but instead you will notice it will add subnet mask information in its updates.

For our lab we have a scenario , in which we have 2 Routers R 1& R2 . network is connected to R1, while Network 192.168.20..0/29 with R2. We will run EIGRP between R1 & R2 and advertise both networks with corresponding subnet masks. But you will notice , by running “sh ip route” command , both Routers will display networks with Classful info i.e network as and as

Next we will disable auto-summary and then finally view output.

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Don’t forget to watch the video tutorial :

IT Funkaar

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