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rakesh roshan
New Member
Tue Dec 25, 2007 3:04 am

regarding ip route

Tue Dec 25, 2007 3:11 am

ip classless
ip route

can you explain me

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Cisco Inferno
Mon Jul 10, 2006 12:58 am

Tue Dec 25, 2007 3:23 am

This definitely doesn't belong in network management, moved to Cisco general...

The 'ip classless' command tells the router to act classlessly, i.e. pay no attention to class of IP addresses (class a, b, c, etc) and instead make its decision-making basis off subnet mask.

The 'ip route' command tells the router to forward all traffic for which it doesn't have a specific route to it's a default route pointing through

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Ultimate Member
Fri May 04, 2007 9:44 am

Tue Dec 25, 2007 7:16 am

Further to what Ian said, you should also ensure that you have "no ip subnet-zero" in your configuration.

Someone had the bright idea back in the very early days of CIDR that the very first and last subnets of any given slash size should be unusable.

What this meant was for /26 size subnet, which is 64 IPs each, or 4 subnets per /24, the first and last /26 were unusable, so you were only getting 50% efficiency from your allocation (if you chose to divide your /24 into /26's).

Likewise if you divided a /24 into /30's, you would only get 62 /30's out of it, instead of the potential 64.

You shouldnt need to worry about either of these being enabled/disabled by default. Classless routing ("ip classless") should always be enabled by default, and Subnet-zero ("no ip subnet-zero") should always be disabled by default.

Im presuming the only real reason the commands still exist is there might be someone out there still using them, for whatever reason!


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