Questions - NAT/ICS And Subnet Mask

proteus71

1. Why can't an ip addy of 199.254.15.35 have a sn mask of 255.255.255.240 (this was an answer to a practice exam)?

2. Can clients going through a NAT or ICS server have static ip addys (read conflicting info on this)?

dynamik

Was there more information to number 1? You have to watch out for the network and broadcast addresses, but 35 isn't either.

Yes for NAT. Technically yes for ICS, but ICS has a mandatory DHCP server, so you could get conflicts and it's not recommended.

undomiel

proteus71 wrote:

1. Why can't an ip addy of 199.254.15.35 have a sn mask of 255.255.255.240 (this was an answer to a practice exam)?

Maybe someone else can correct you who knows more about subnetting than I but that looks perfectly valid to me as it is within the host range and avoids the broadcast address.

2. Can clients going through a NAT or ICS server have static ip addys (read conflicting info on this)?

Clients can use static addresses with NAT & ICS. They just need to point toward the ICS system for their gateway.

nicklauscombs

#1 Unless the question had some specifics about which addresses you couldn't use, I don't see any reason why it wouldn't be valid

proteus71

Thanks for the info.

As for #1, the answer stated "There is no way a workstation with an IP address of 199.254.15.35 can use a subnet mask of 255.255.255.240". I'll think of this as a bad question. I don't see any other info in the question that would cause this.

snadam

proteus71 wrote:

Thanks for the info.

As for #1, the answer stated "There is no way a workstation with an IP address of 199.254.15.35 can use a subnet mask of 255.255.255.240". I'll think of this as a bad question. I don't see any other info in the question that would cause this.

uhhh, I don't think you can have an IP addy of 199.254.15.35 with a subnet mask of 255.255.255.240. The highest number in the 4th octet (sans the broadcast address is 14. the 4th octet in the subnet mask (.240) uses 4 of 8 bits. For it to add up to 35 it would need some bits on the network side of the address (specifically the '32' needs to be turned on)


255.255.255.240

11111111.11111111.11111111.1111|0000

199.254.15.35

11000111.11111110.00001111.0010|0011

the conflicting bit is in RED

dynamik

Wait... but you keep incrementing the subnet bits.

You had me all confused for a second there.

That just means that the first four bits are used for the subnet. So:

0000 would be 0-15
0001 would be 16-31
0010 would be 32-47
0011 would be 48-63
etc.

That's why I asked if there was more info. You'd be right if it was asking about anything other than the third subnet.

snadam

dynamik wrote:

Wait... but you keep incrementing the subnet bits.

You had me all confused for a second there.

That just means that the first four bits are used for the subnet. So:

0000 would be 0-15
0001 would be 16-31
0010 would be 32-47
0011 would be 48-63
etc.

That's why I asked if there was more info. You'd be right if it was asking about anything other than the third subnet.

very true! I didn't think about those factors! The network address he is trying to subnet could very well be 199.254.15.32\24. But based on the info given, I couldn't think of any other way.