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| Member Join Date: Dec 2004
Posts: 54
Certifications: BS in IS, AAS in NT, AAS in B.S.A., A+, & MCP (70-270, 70-290), MCTS (70-642)  |
 Number of Available subnets? Does anyone know the number of available subnets for these network IDs? Network ID 207.209.68.0 /27 131.107.0.0 /20 10.0.0.0 /13 208.147.66.0 /25 These are my answerse, please let me know if it's correct. The reason why I'm asking is because on the answer sheet it shows something else. Any help would be appreciated. Thank you. 207.209.68.0 /27 - my answer is 8 131.107.0.0 /20 - my answer is 16 10.0.0.0 - my answer is 24 208.147.66.0 /25 - my answer is 8 | ||
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| New Member Registered Member  Join Date: Jul 2006 Location: Chicago, IL
Posts: 3,376
Certifications: A+, Network+, MCSE:M 2003, MCITP: Enterprise Messaging Administrator, MCTS: OCS (Conf/Voice)/Hyper-V, Exchange MVP, B.S. |
207.209.68.0 /27 131.107.0.0 /20 10.0.0.0 /13 208.147.66.0 /25 207.209.68.0 /27 = Class C = Default of /24 = 3 available bits for subnets = 2^3=8 subnets 131.107.0.0 /20 = Class B = Default of /16 = 4 available bits for subnets = 2^4=16 subnets 10.0.0.0 /13 = Class A = Default of /8 = 5 available bits for subnets = 2^5=32 subnets 208.147.66.0 /25 = Class C = Default of /24 = 1 available bit for subnets = 2^1=2 subnets __________________ “For success, attitude is equally as important as ability.” - Harry F. Banks | ||
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| Senior Member Registered Member  Join Date: Jul 2006 Location: San Diego
Posts: 334
Certifications: A+, MCP 70-270,290, CCNA.  |
Wow, this really helps alot. Thanks All! Although I continue to struggle with subnetting, I am still trying my best and this really does help. Thanks again.  __________________ A+, MCP(270,290), CCNA MCITP Track 70-640 <Currently studying 70-642 70-643 70-647 | ||
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| New Member Registered Member Join Date: Jul 2006 Location: Chicago, IL
Posts: 3,376
Certifications: A+, Network+, MCSE:M 2003, MCITP: Enterprise Messaging Administrator, MCTS: OCS (Conf/Voice)/Hyper-V, Exchange MVP, B.S. |
Here's a thread from a about a couple months ago. This might help you understand subnetting a bit more. If you still don't get it, let me know, i'll help you out. http://www.techexams.net/forums/viewtopic.php?t=16824 __________________ “For success, attitude is equally as important as ability.” - Harry F. Banks | ||
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| Member Registered Member Join Date: Jan 2003 Location: Houston
Posts: 55
Certifications: AS in Computer Science, A+, Network+, MCP 270 & 290, Linux+, (291-Pending) |
I dont see how or what the /20 is after an IP address WTF does it mean. I'm lost on this issue it's like reading a different language or something.  Update: After using google and finding http://www.cisco.com/warp/public/701...#ustand_subnet  I now understand that the number just represents the number of bits used to make the subnet mask.  Example: /20 In English means: 11111111.11111111.11110000.00000000 =255.255.240.0 for the Subnet. Example: /27 In English means: 11111111.11111111.11111111.11100000 =255.255.255.224 for the Subnet. Oh they have a cool link has a nice PDF option off to the right. __________________ Don't tell co-workers your going for a Cert that they don't have. They may think your trying to take their job. | ||
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| New Member Registered Member Join Date: Jul 2006 Location: Chicago, IL
Posts: 3,376
Certifications: A+, Network+, MCSE:M 2003, MCITP: Enterprise Messaging Administrator, MCTS: OCS (Conf/Voice)/Hyper-V, Exchange MVP, B.S. |
It basically means the subnet mask will have 20 consecutive 1s. 1111111.11111111.1111.0000.00000000 255.255.240.0 The bits are as follows 128 64 32 16 8 4 2 1 Since the 3rd octet is 11110000, that means the 4 left most bits are turned on. Therefore we take 128 + 64 + 32 + 16 = 240. __________________________________________________ ________ So a real world example? Well I just created a bunch of static routes the other day to have ISA talk to a bunch of internal VLANs, so I'll talk about that. The client had a bunch of internal VLANs on different networks such as 172.16.0.0/16, 172.17.0.0/16, 172.18.0.0/16, and so on. /16 means that the subnet mask is 16 consecutive 1s 1111111.1111111.00000000.00000000 255.255.0.0 The IP is 172.16.0.0 Because the network bits on a subnet mask are all consecutive 1s on both the 1st and 2nd octet, if you change anything in the 1st or 2nd octet of an ip, it'll belong on a different network. This can be proven by using the ANDing process. 172.16.0.0 vs 172.17.0.0 1st octet will obviously match 16 - 00010001 vs 17 - 00010000 Since everything matches but the last bit, we can see that they are on a different network. This is where the /16 plays in. It gives us the subnet mask which allows us to see how many bits to use to determine if ips are on a different network by using the ANDing process. Does this make any more sense or am I mixing 10 different languages together and trying to form a new language that you've never heard of? __________________ “For success, attitude is equally as important as ability.” - Harry F. Banks | ||
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| Senior Member Registered Member Join Date: Apr 2007 Location: D.C.
Posts: 233
Certifications: MCP (70-290, 70-291) |
Quote:
Not sure if this will help clear up anything, but some info in a thread I started a few weeks ago (http://www.techexams.net/forums/viewtopic.php?t=24568) explains some of the information discusses above in a different way -- not sure if it'll help or not, but worth looking over if it'll make things 'click'  __________________ Currently Studying: 70-293 Last Pass: 70-291 | |||
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