Solved: What class does this IP address belong?

alfonzofernando · ‎02-11-2007

30.10.10.1/24

first octet 30 (Class A )

subnet mask is /24 (Class C)

so is this a class A address or class C address?

or subnetted class A address?

thank you in advance for all responses

albert.remo · ‎02-11-2007

Hi!

Good Day!

Generally, the IP address that you provided is a Class A network. What we are dealing here is Variable Length Subnet Masks (VLSM). Giving a subnet that is different than the usual to be able to come of with a larger number of networks that supports a smaller number of hosts (long masks) or vise versa. VLSM was created to find ways to use address space more efficiently. VLSM runs on Cisco routers with IOS that supports it. Several routing protocols such as RIPv2, EIGRP and OSPF also supports VLSM.

So you're right, this is a subnetted Class A network.

Please see link below for additional reference:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml

Hope this helps,

Regards,

Albert

View solution in original post

scottmac · ‎02-11-2007

When talking IP address Class, there is ONLY one thing used: the leading bits of the leading byte (the most significant bits of the most significant byte - the ones all the way on the left).

The mask has absolutely nothing to do with the class of an address.

Leading bits:

0xxxxxxx - Class A

10xxxxxx - CLass B

110xxxxx - Class C

1110xxxx - Class D

You have a Class A address there.

30 = 00011110

Good Luck

Scott

alfonzofernando · ‎02-11-2007

thanks scott

so how should I define the below address according to network terminology(beside it is class A):

30.10.10.1/24 (this is definetly different from 30.10.10.1/8)

what I understand is; 30.10.10.1/24 is a class A address but when we mask it with 255.255.255.0 we create subnet on a Class A address?

tx in advance

albert.remo · ‎02-11-2007

Hi!

Good Day!

Generally, the IP address that you provided is a Class A network. What we are dealing here is Variable Length Subnet Masks (VLSM). Giving a subnet that is different than the usual to be able to come of with a larger number of networks that supports a smaller number of hosts (long masks) or vise versa. VLSM was created to find ways to use address space more efficiently. VLSM runs on Cisco routers with IOS that supports it. Several routing protocols such as RIPv2, EIGRP and OSPF also supports VLSM.

So you're right, this is a subnetted Class A network.

Please see link below for additional reference:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml

Hope this helps,

Regards,

Albert

alfonzofernando · ‎02-11-2007

hi Albert, tx for great explanation. everything is clear now.