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No Ip classless command?

can someone tell me What is the major effect on routing of configuring your routers with the ‘no ip classless’ command?

thanks in advance!!!

1 REPLY
Purple

Re: No Ip classless command?

Hi,

The 'no ip classless' command makes your router work in a classful fashion. The impact of using this is that there is a likelihood that some subnets will be black-holed.

Here's an example:

- 'no ip classless' is enabled

- there are two routes in the routing table:

10.1.1.0/255.255.255.0

0.0.0.0/0.0.0.0 (default)

- If your router receives a packet with a destination of 10.20.1.1, it will discard the packet instead of using the default route. This is because a subnet of the 10.0.0.0/8 classful address exists in the routing table (the 10.1.1.0/24 subnet). The router assumes that that is all there is to know about the 10.0.0.0/8 network. Any other subnets of 10.0.0.0/8 are considered unreachable (unless specific routes for those are present as well).

- if 'ip classless' were configured instead, the default would have been used.

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

Paresh

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