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255.255.255.255 - as subnetmask

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15 years 11 months ago #28187 by dentys
i have a big lan. a few hundred pc's.....a little over thousand :P
i just need ppoe.
i do not see the reason not to use this netmask. i did not find anywhere anything about using that netmask. is it ok? what could go wrong with this setup? if any computer needs to talk to anothe..it will do this thru the gateway ( wich wil have the subnet mask for all the ip's for wich is doing the routing)
am i wrong anywhere?
what could go wrong?
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15 years 11 months ago #28192 by Chojin
Your gateway needs to be in the same subnet as your host.

with a /32 (255.255.255.255) subnet you don't have a subnet only a host-only network.

The 255.255.255.255 is used for routing most of the times. If you want to have a specific route going to one or another interface you will use /32.

CCNA / CCNP / CCNA - Security / CCIP / Prince2 / Checkpoint CCSA
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15 years 10 months ago #28477 by menshaco
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15 years 10 months ago #28494 by Kajitora
255.255.255.255 is not a valid subnet for an Interface.

When you put in ip information your are saying "Use this ip in this range" Well, the range is litterly 0. So there are no avialble IPs in the range. The lowest usable subnet is /30 or 255.255.255.252.

The reason you can not use /31 is because it only leaves 2 avialble address, and you always have to have a address for broadcast and network. /30 leaves 4 address, and is normaly used for Point to Point style connections.

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15 years 10 months ago #28502 by SteveP
My only experience of using a /32 mask is when configuring a loopback.
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15 years 10 months ago #28537 by Chojin

255.255.255.255 is not a valid subnet for an Interface.

When you put in ip information your are saying "Use this ip in this range" Well, the range is litterly 0. So there are no avialble IPs in the range. The lowest usable subnet is /30 or 255.255.255.252.

The reason you can not use /31 is because it only leaves 2 avialble address, and you always have to have a address for broadcast and network. /30 leaves 4 address, and is normaly used for Point to Point style connections.


/32 IS a valid subnetmask.. you can use it on any interface you prefer.

/32 == 255.255.255.255
/31 == 255.255.255.254

/30 is indeed the lowest usable for IF you want to have a PtP connection or 2 hosts in a subnet, but we are not talking specificly about a network.

CCNA / CCNP / CCNA - Security / CCIP / Prince2 / Checkpoint CCSA
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