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Customer says they only got 32 IPs when they should have got 64 (running config displayed here)

M

Mucman

Diamond Member
This person says that the higest IP he can configure is .31, here is the config in the router :

interface FastEthernet0/0.12
description Publish Button
encapsulation dot1Q 12
ip address 66.51.174.1 255.255.255.192
no ip redirects
no ip unreachables
no ip proxy-arp
no ip mroute-cache
no cdp enable

call me crazy, but isn't a /26 64 IPs? the last octect of the mask is 11000000, and 6 0's means 2^6 IPs can be configured.
 
You are absolutely correct - a /27 bit mask will allow them to use 64 IP's. Make sure they are assigning the right mask to their PC's.

One detail - Technically, this is an illegal address. Do you have ip subnet-zero enabled on the routers?

- G
 
OK, Garion you confused me... First you said I am correct, and then you said a /27 mask is 64 IPs 🙂 They said they were using the right mask, but I
will double check later on.


ip subnet-zero is enabled... I am not a fan of that, but that is how it has been configured since I started here. 0 subnets drive me batty when trying
to work out the bitwise math in my head 🙂
 
good link

Well that confirms that it is setup properly then... and now I don't need to to it all in my head too 😛, so router side configuration looks
ok then. I guess I will call to let em know that they have been sniffing glue and entering the wrong subnet.
 
What happens when they try to configure the other 32 ip's? Do they not route, or he can't physically configure them on his machines or what? Call me crazy but, have you tried pinging any of the other 32 ip's to see if they are in use? When I was working for an ISP, I ran into situations such as this quite often. Somebody would mess up the documentation, and IP's were assigned that were in use by another customer. So, for example. if you gave them 66.51.174.0 /26, but some other customer has 66.51.174.32/ 27, guess what? you're screwed. Or, they are using 255.255.255.224 on their LAN instead of 255.255.255.192.
 
pcmark - I have checked our docs... We had that whole 66.51.174 class C until the customer left. No one is on any of the other IPS. Heck I can ping 66.51.174.63 (broadcast IP) and I get a response. The client said that he tried configuring IPs from 62 down until he hit .31. That doesn't make sense either because if they had a /27 then .31 would be the broadcast IP. The client claims that he knows what he is doing and that he has the subnet mask set at 255.255.255.192.
 
Mucman, technically speaking, you really only have 62 addresses available because you don't include the network or broadcast address (The network address would end in 11000000 and the broadcast would end in 11111111). So (2 ^ 6) - 2 = 62 total ip addresses available for that particular subnet.

 
Phokus - Well, you know what I mean 🙂, There are still 64 IPs for that subnet... just 2 of em reserved. Like I said, I can ping their broadcast IP and it responds.
 
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