Command "ip classless' on Cisco

I see an comman "ip classless" on Cisco router, and I don't know what does it use for? How can you help me?
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In short

ip classless command in global configuration mode makes the Cisco IOS software forward packets destined for unrecognized subnets to the best supernet route possible

Ip classess is used to tell the router not to route to the classfull boundary of the Ip address subnet mask.

the classful boundard are.
for class a
class b
class c

It works in conjunction with the routing protocal used on the router.

for example if you use a classless routing protocol such as eigrp and have subnets

and have subnets

when you type router eigrp 100

and put in your networks

instead of putting the classfull network number such as

yiou would put as your networks and

this will help routing if the subnets are all not connected to one router.

however is you use a classful protocol such as RIP or igrp

even if you type in your networks as, .32, and .64

when you do a show run command

the only network address you will see under the protocol would be, the classfull address.

if your network was subnetted on diferent routers, the classfull protocol would not work.

reason being both routers think they are connected to the same network and when routing updates are sent to eachother, one router is saying i am connected to the network while the other one is say no, i am connected to the network because even when you put in your subnet address it will automatically trunkate the address to its classfull boundary

ip classless stops that from happening to allow routing between subnets.

hope this was a good explaination of IP classless

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