""Wojtek Zlobicki"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > And if you are allowing IP subnet-zero, then you have subnets=(2^18)-1 or > > 262143 subnets. > > Does ip subnet zero also not allow an all ones subnet , making the total > 262144 (can't remember in which IOS this started becoming possible)
No, IP subnet-zero does not "allow" this capability. On a Cisco router, you are always allowed to use the all-ones subnet. IP subnet-zero has nothing at all to do with the all-ones subnet. You can prove this to yourself by firing up a router and creating a loopback address that has an all-ones subnet address, while alternatively turning on and turning off IP subnet-zero, and you will find that it makes absolutely no difference whether it's on or off. The big problem with using the all-ones subnet is that there is the opportunity for great confusion as to whether a packet sent to the broadcast address is meant for just the subnetted network or for the entire classful network. This is why it is generally held that the all-ones subnet should not be used, and this is why basic networking texts do not count the all-ones subnet as a valid subnet. But if you really find youself in a jam because you're running out of addresses, and you use great caution, you could in theory fire up the all-ones subnet. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=23653&t=23632 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
