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Old 03-24-2009, 12:05 AM   #1
trist007
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Two questions that I had on my mind about linux...


1. I've been rebuilding my kernel and trying different options. I have a intel Q6700, which is obviously a quad core processor. It is my understanding that SMP which stands for Symmetric Multi-Processor is an option in the config of the kernel. So since I have a 1 single processor that is a quad core, I would be unable to benefit from that option. However, I get the weird feeling that even ppl with dual and quad cores select this option. I have selected it, and my computer seems to run quite nicely. So my question is, can quad or dual cores, even though they are only 1 processor, take advantage of the SMP kernel?

2. I don't completely understand when people say their ip range is
192.168.1.0/24. I know that 0/24 stands for 1-254 right? 255 would be reserved for broadcast. Could somebody explain this part better. I'm thinking it has something to do with 24 bits.
 
Old 03-24-2009, 12:19 AM   #2
billymayday
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On 2, your IP is a 32bit address, so /24 is equivalent to a netmask of 255.255.255.0

Hence, 192.168.1.0/24 represents the range 192.168.1.0-192.168.1.255, whereas 192.168.0.0/16 represents the range 192.168.0.0-192.168.255.255.

The /x represents the significant bits.
 
Old 03-24-2009, 12:21 AM   #3
jman82s
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1. Modern consumer multicore chips [I]do[I] in fact take advantage of SMP!! Leave it on!

2. The /24 part of the ip address is what's called a 'netmask', which determines the ip range of a subnet. There's some somewhat complicated math involved--not bad once you do it a few times--that converts that 24 into octets, and is 'and'ed or 'or'ed, or both, can't remember, with the ip address. A subnet makes a network within a network.
 
Old 03-24-2009, 12:23 AM   #4
vindoan
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A quad core is four processor core in one processor package. So your quad core will benefit from SMP.
 
Old 03-24-2009, 12:23 AM   #5
reptiler
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You need SMP-support to have all your cores working.
The MP in SMP may mean Multi-Processor, what else is a Multi-Core-CPU of not actually multiple CPUs glued together (and sharing cache instead of each having their own)?

I guess that for the OS it's no difference if you have a couple of different CPUs or just one CPU with multiple cores, thus: Yes, you benefit from the SMP-option, because otherwise you'll be only using one core.

Just try this:
1. cat /proc/cpuinfo | grep vendor_id | wc -l
2. Then build and boot a kernel without SMP-support.
3. Try #1 again.
 
Old 03-24-2009, 12:27 AM   #6
trist007
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So in 192.168.1.0/24, the 192.168.1 are the network ID and the 0-255 would be the host ID, which consists of the network within the 192.168.1 network.

So in 192.168.0.0/16, the 192.168 are the network ID and the 0-255,0-255 would the host ID, network within the 192.168 network.

This about right?

So let's say there's a box running a IP of 192.168.1.12, he would not be able to communicate with a box running a IP of 192.168.0.12, because the first is on a 0/24 or 255.255.255.0 subnet while the latter is on a 0/16 or 255.255.0.0 subnet.

This about right?

Yeah
cat /proc/cpuinfo | grep vendor_id | wc -l gives me 4

Last edited by trist007; 03-24-2009 at 12:30 AM.
 
Old 03-24-2009, 12:41 AM   #7
reptiler
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Quote:
Originally Posted by trist007 View Post
Yeah
cat /proc/cpuinfo | grep vendor_id | wc -l gives me 4
And a kernel without SMP-support will give you 1.
 
Old 03-24-2009, 01:08 AM   #8
vindoan
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Quote:
Originally Posted by trist007 View Post
So in 192.168.1.0/24, the 192.168.1 are the network ID and the 0-255 would be the host ID, which consists of the network within the 192.168.1 network.
192.168.1.0 is the network. There is also an IP address reserved for the broadcast, 192.168.1.255. You can assign IPs for hosts in the range, excluding the network and broadcast.

Quote:
Originally Posted by trist007 View Post
So in 192.168.0.0/16, the 192.168 are the network ID and the 0-255,0-255 would the host ID, network within the 192.168 network.

This about right?
In a 192.168.0.0/16 network you have 65534 usable IP's. Your first usable IP is 192.168.0.1 and your last usable IP is 192.168.255.254. The broadcast address is 192.168.255.255. Conventionally, people use 192.168.*.* address for private class C networks. Hence 192.168.0.0/16 is hardly ever seen.


Quote:
Originally Posted by trist007 View Post
So let's say there's a box running a IP of 192.168.1.12, he would not be able to communicate with a box running a IP of 192.168.0.12, because the first is on a 0/24 or 255.255.255.0 subnet while the latter is on a 0/16 or 255.255.0.0 subnet.

This about right?
In theory the two boxes should be able to communicate. 192.168.1.0/24 is a what you call a VLAN of 192.168.0.0/16. Though you might have to put a route in there.

Last edited by vindoan; 03-24-2009 at 01:12 AM.
 
  


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