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Is there mask for class D ip address? As it is for multicast, I am not sure about it. I read somewhere that D ip addressas are 32-bit network addresses and they dont have hostID, but in the following link I read that the number of bits for network and host is undefined in the class D. I am a little confuse a bout it, would you please guide me?
Roshio
Posted 2011-05-27T08:10:03.920
Reputation: 147
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First classful addressing isn't used anymore, it's classless now.
Class D like any other Classes, all IPv4 addresses , are 32-bit.
Now, Judging by this link.. http://www.tcpipguide.com/free/t_IPMulticastAddressing.htm
it doesn't have network and host bits. If it's a multi-cast address then one IP would go to multiple machines anyway 'cos they'd all have that IP.
That tcpipguide link about Class D addresses has a table with more than the table on the wikipedia page on classful addressing.
I suppose in this case not defined means no network fields and host bit fields which is what you say you read, which makes sense and I think that's what the wikipedia page really meant when it said undefined. There are also going to be some addresses that IANA never assigned..but no doubt some multi-cast addresses were given out.
I don't know if you'd call the whole thing a network address. Network address is normally an address ending in .0 representing the subnet. I don't think a multi-cast address is referred to as a network address.
barlop
Posted 2011-05-27T08:10:03.920
Reputation: 18 677
So,As we know there are mask for classes A: 8 bits, class B: 16 bits and class C : 24 bits, can we say that the number of bits for class D is undefined? – Roshio – 2011-05-27T09:06:17.813
they're all 32-bit. Class A has an 8 bit network portion , Class B a 16-bit network portion. Class D doesn't have a network and host portion. – barlop – 2011-05-27T09:13:08.167
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A netmask is used to divide an IP address into a network part and a host part. Multicast addresses don't have network parts and host parts, so it is meaningless to talk about a netmask.
A multicast address is just a 32-bit address within a well-known range that hosts subscribe to using a protocol such as IGMP.
Tom Shaw
Posted 2011-05-27T08:10:03.920
Reputation: 376
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Class D IP addresses have the first four bits set to 1110, the rest of the bits are available. So the range for class D addresses is from 224.0.0.0 to 239.255.255.255.
And the netmask will be 11110000.00000000.00000000.00000000 in binary and 240.0.0.0 in decimal.
Quentin
Posted 2011-05-27T08:10:03.920
Reputation: 156
The first 4 bits are that..the class ID. I think the class ID only makes part of the network id. Also 15.255.255.255 is Class A. Class D covers a higher range than that. I'm not sure what routers/where would zero out just the class ID.. where did read that? – barlop – 2011-05-27T08:27:33.490
@barlop 15.255.255.255 is not a IP address but the netmask of the range for class D addresses. Source Wikipedia.
– Quentin – 2011-05-27T08:35:20.790@Quentin Can you be more specific when you make a reference? 15.255.255.255 is not mentioned on that page, neither even is the word netmask. – barlop – 2011-05-27T08:37:05.613
I can see you're zeroing out the first 4 bits.. but i'm not sure what routers do that. I suppose some might, if one router did a mask of 11110000.0.0.0 and sent Class A to one router Class B to another e.t.c. then one of those routers dealing with just one Class, could do that. Though classes aren't used anymore doing so may be useful but anyhow also, I don't see how mentioning the netmask(assuming that's the right term) is relevant to the question though. – barlop – 2011-05-27T08:43:31.380
So,As we know there are mask for classes A: 8 bits, class B: 16 bits and class C : 24 bits. So, what is the number of bits for a D class? – Roshio – 2011-05-27T08:45:13.640
The netmask is normally on the first bits, not the end bits. So if there was a netmask, it would be 240.0.0.0. But for multicast there is no distinction between network and host so it's meaningless. – Tom Shaw – 2011-05-27T08:46:07.367
@rayan well, they're all 32-bit. Class A has an 8 bit network portion. i'd suggest that perhaps Class D it seems doesn't have a network and host portion. – barlop – 2011-05-27T08:47:26.133
@barlop I understood the question as "What is the netmask for class D addresses ?"... @Tom You are right, I switched it. Let me edit my answer. – Quentin – 2011-05-27T08:48:17.897
@Quentin Where did you read that Class A/B/C/D addresses have "a netmask"? – barlop – 2011-05-27T08:56:21.597
@barlop I guess a mask to filter all addresses of one class. – Quentin – 2011-05-27T08:58:54.570
I don't think his question was "what is the netmask for Class D Addresses". And secondly, even if you edited it to 240.0.0.0 as you suggest.. It's likely that is wrong again. Look here http://www.tcpipguide.com/free/t_IPDefaultSubnetMasksForAddressClassesABandC.htm The "default subnet masks"(why he says default I don't know) are 255.0.0.0 or 255.255.0.0 or 255.255.255.0 so for Class D and E it's probably 255.255.255.255 if there is even a subnet mask at all. And "netmask" isn't really the right terminology anyway.
– barlop – 2011-05-27T08:58:57.850@Quentin, I think you misinterpreted me. I was referring to the general technique of working out the netmask, but as I say in this case it is meaningless. @barlop is on the right track. – Tom Shaw – 2011-05-27T09:05:02.897
@barlop, @Tom : You may be right. I am new to SuperUser, what should I do ? Delete my answer or just wait that some better ones will be rated up ? – Quentin – 2011-05-27T09:08:56.670
I don't know.. it's not emergency. the comments poke and point out the deficiencies or possible deficiencies. maybe somebody might comment clearing things up here, you could then edit it with a note creditting the person that corrected it. and somebody might give a better answer too. – barlop – 2011-05-27T09:10:01.853
but without yet knowing what to correct it with it's tricky to do so. – barlop – 2011-05-27T09:16:13.490
@Quentin don't delete the answer 'cos it's useful to have a wrong one with lots of comments! in future maybe if you're v unsure it's better to put it as a comment lest it be downvoted! but in this case anyway with lots of comments that signifies the problem with it.. no need for anybody to downvote it! – barlop – 2011-05-27T09:21:46.860
It looks like you read right. "I read somewhere that D ip addressas are 32-bit network addresses and they dont have hostID," ok you're wrong that it's a 32-bit network address. Network address is something else, network address is an IP ending in .0 But on the other aspect it seems you're right that Class D doesn't have a network and host portion. Maybe was a good source you read. Where did you read that? – barlop – 2011-05-27T09:14:24.550
you are righ, I made a mistake. I got the site material wrong. http://www.paessler.com/support/kb/questions/34
– Roshio – 2011-05-27T10:10:21.390