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 Calculating IPv4 Subnets - Have i got this right?
 (#1) (.)(.) Banned   Videocard: GTX 970 Processor: i72600k @ 4.7 Mainboard: Asus M4E Memory: Corsair Vengence 10gb Soundcard: onboard PSU: Enermax Rev 1250w Calculating IPv4 Subnets - Have i got this right? - 02-03-2015, 13:00 | posts: 9,098 | Location: NZ Decimal Binary IP Address ...| 192.168.10.131 .| 11000000.1010100.00001010.10000011 Subnet Mask | 255.255.255.192 | 11111111.1111111.11111111.11000000 To find the Network Address(Nw)..IP - 11000000.1010100.00001010.10000011 Sub-11111111.1111111.11111111.11000000 Nw -11000000.1010100.00001010.10000000. (192.168.10.124) 7 bits for hosts? If so, the first usable Add is 192.168.10.125 and the last is found by inverting the host portion of the address -10000001 (.125) to 11111110(254). Network Address - 192.168.10.124 First - 192.168.10.125 Last - 192.168.10.254 Broadcast - 192.168.10.255 Have I got that right?
(#3)
scatman839
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02-03-2015, 13:20 | posts: 13,143 | Location: Scotland

.192 has 64 hosts, so you would do blocks up 64

N 0
F 1
L 62
B 63

n 64
f 65
l 126
b 127

n 128
f 129
l 190
b 191

n 192
f 193
l 254
b 255

your ip is in the third block

as mentioned, you can't go between subnets, you go up until you find the first subnet block that is lower than your ip, (128 in this case) then work from there (add 64 for the next network, -1 for broadcast, -2 for last usable)

personally I avoid writing it out in binary and draw up a subnet chart (forum removing extra spacing ugh)

slash notation /25 /26 /27 /28 /29 /30 /31 /32
no of hosts 128 64 32 16 8 4 2 1
subnetmask 128 192 224 240 248 252 254 255

I realise this doesn't work as great if the subnet is for a smaller number of hosts, say, 8 or 4. In that case, get your IP, divide it by your no of hosts (that you find using the subnet mask value given), discard the remainder, then multiply that back by the no of hosts.

e.g
131/64=2.046875
2*64=128

Also, you're probably about to be taught 4-5 subtly different ways of subnetting, pick whatever you find best, I know my method doesn't work for as many people(especially the dividing and remainder stuff). It took me about a year of practise to start getting it done in my head

Your error however was converting 10000000 into decimal wrong, 128 not 124 (not sure how you got there), had you started at 128 you would have been on the right track, but I don't think this is right
Quote:
 and the last is found by inverting the host portion of the address
never seen that before and in this case it doesn't work, 192 is 11000000

Last edited by scatman839; 02-03-2015 at 13:40.

 (#4) (.)(.) Banned   Videocard: GTX 970 Processor: i72600k @ 4.7 Mainboard: Asus M4E Memory: Corsair Vengence 10gb Soundcard: onboard PSU: Enermax Rev 1250w 02-03-2015, 14:13 | posts: 9,098 | Location: NZ So forth octet being 192, which is a /26 with 64 addresses, I could just - 192 - 64 = 128 + 63 = 191. The NA is .128 then first and last usable are .129 and 190, broadcast as the .191, with the next network starting at .192? @scatman839 Yeah i dont know where i pulled 124 from. Im using something like you had and doing this, but got 124 in my head instead of 192. 128--64--32--16--8--4--2--1 -1----1---0---0--0--0--0--0 <-------192) As for the inverting stuff, its in one of the exercises we were given. Theres so many ways of doing it and without warning, the workbook explaining it all changes what method of converting its using when explaining things. So first i have to work out which methods its used (thats not even apart of the god damn exercise/example) before i can understand how the workbook has come to the answer it has in its example. Last edited by (.)(.); 02-03-2015 at 14:22.
 (#5) allesclar Ancient Guru     Videocard: Nvidia GeForce GT 540M Processor: Intel Core i7 2670QM Mainboard: Samsung BA92-07584A Memory: Corsair 16GB DDR3 1333MHz Soundcard: Onboard PSU: N/A 02-03-2015, 14:23 | posts: 5,350 | Location: England Yup.
(#6)
scatman839
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02-03-2015, 14:26 | posts: 13,143 | Location: Scotland

Quote:
 Originally Posted by (.)(.) So forth octet being 192, which is a /26 with 64 addresses, I could just - 192 - 64 = 128 + 63 = 191. The NA is .128 then first and last usable are .129 and 190, broadcast as the .191, with the next network starting at .192?
bingo
Quote:
 Originally Posted by (.)(.) @scatman839 Yeah i dont know where i pulled 124 from. Im using something like you had and doing this, but got 124 in my head instead of 192. 128--64--32--16--8--4--2--1 -1----1---0---0--0--0--0--0 <-------192) As for the inverting stuff, its in one of the exercises we were given. Theres so many ways of doing it and without warning, the workbook explaining it all changes what method of converting its using when explaining things. So first i have to work out which methods its used (thats not even apart of the god damn exercise/example) before i can understand how the workbook has come to the answer it has in its example.
Our lecturer taught us one way, cisco tried to teach us another way, another lecturer apparently teaches a third way.

Basically any time I come across cisco trying to tell me how to subnet again in ccna I just ignore it and use the numbers it gives

It's up to you if you want to try learning the other method, but it might just confuse you further

 (#7) (.)(.) Banned   Videocard: GTX 970 Processor: i72600k @ 4.7 Mainboard: Asus M4E Memory: Corsair Vengence 10gb Soundcard: onboard PSU: Enermax Rev 1250w 02-03-2015, 14:38 | posts: 9,098 | Location: NZ Yeah thats the issue ive got atm, the lecturer method vs the internal exercises method vs Cisco method. Im soo tired. Thanks for that gurus. I'll keep at it.
(#9)
(.)(.)
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02-04-2015, 11:08 | posts: 9,098 | Location: NZ

Thanks Veteran.
Quote:
 You need to be very good at subnetting, acl's (access control lists) and vlans. Become good at these and your 75% of the way there but without becoming good at these you may as well forget it.
Almost word for word what our lecturer said to us today!

Those packet tracers are a bit odd at times. It'll ask you to do something, like assign ip addresses to switch 1 for the first part, but then you go to click on it and it says its locked. Then further down in part 3 it'll say something like "Since Switch 1 is pre configured, just assign the remaining ips manually...". Eh, why didnt you say so at the top, i thought i was doing something wrong. Oh well.

This command come in handy at times i reckon:
Router#show cdp neighbors detail

 (#10) allesclar Ancient Guru     Videocard: Nvidia GeForce GT 540M Processor: Intel Core i7 2670QM Mainboard: Samsung BA92-07584A Memory: Corsair 16GB DDR3 1333MHz Soundcard: Onboard PSU: N/A 02-04-2015, 11:22 | posts: 5,350 | Location: England Not just those, you also, for the Cisco exams, need to be **** hot on the commands that are used within the command prompts on Cisco equipment.
 (#11) PNeV Maha Guru     Videocard: MSI GTX 1070 Armor OC Processor: 3570K @ 4.4GHZ Mainboard: ASRock Extreme4 Z77 Memory: 16GB Kingston HyperX Fury Soundcard: Onboard & M-Audio AV40 PSU: Antec HCG M 620W 02-04-2015, 12:53 | posts: 2,072 | Location: Northampton, United Kingdom I remember using Packet Tracer for an assignment at University for a project that involved the setting up and subnetting of an Office Network and it had various requirements such as this Network can access this server, but this Network can't etc. Long story short, it randomly crashed on me and lost a good chunk of work. No warnings, no errors, nothing. Just closed. My advice, save often!
 (#12) scatman839 Ancient Guru     Videocard: 7970m/970 Mini, KD55XD800 Processor: i7 3610QM/i5 6500 Mainboard: HM77/B150M-C Memory: 12GB D3/16GB D4 Soundcard: Via HD, x-530 PSU: 180w/RM650x 02-04-2015, 15:40 | posts: 13,143 | Location: Scotland Had that once while doing a practise skills assessment, never happened before so I didn't even think it possible. No real autosave in the program, but I was working off scenarios I had already made with 3 stages set up.
(#13)
Veteran
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02-05-2015, 18:49 | posts: 12,074 | Location: United kingdom

Quote:
 Originally Posted by (.)(.) Thanks Veteran. Almost word for word what our lecturer said to us today! Those packet tracers are a bit odd at times. It'll ask you to do something, like assign ip addresses to switch 1 for the first part, but then you go to click on it and it says its locked. Then further down in part 3 it'll say something like "Since Switch 1 is pre configured, just assign the remaining ips manually...". Eh, why didnt you say so at the top, i thought i was doing something wrong. Oh well. This command come in handy at times i reckon: Router#show cdp neighbors detail
Someone keeps deleting my posts for some reason.
Anyhow CDP Neighbours i actually turn off on real hardware as it can be a slight security risk. I use it to plan out a network or troubleshoot but i always disable after. Alot of engineers disagree and leave it turned on. Its a 2 way argument both with plausible reasons why to leave enabled and why not too leave enabled.

(#14)
TekkMarine
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02-05-2015, 20:19 | posts: 1,287 | Location: United Kingdom

Quote:
 Originally Posted by (.)(.) Thanks Veteran. Almost word for word what our lecturer said to us today!
Cyber Security & Forensics?, Network Administration?

 ipv4 Subnetting
 (#15) ManYou Newbie   Videocard: 2GB Processor: Intel Core i3 Mainboard: Memory: Soundcard: PSU: NA ipv4 Subnetting - 06-01-2017, 21:38 | posts: 1 You are using Class C ip address 192.168.10/24 address 6 bit for host means you have 2^6 - 2 =64 host ip address in a subnet your subnet is 255.255.255.192 so your subnet range is 0-63,64-127,128-191,192-255. every subnet first IP is network ID and last Ip is broadcast ID. so 192.168.10.0 is subnet id of first subnet 192.168.10.63 is broadcast id of first network suppose if your subnetmask is 255.255.255.224 Total number of host ip in one subnet 2^5-2=30 subnet range=0-31,32-63,64-95,...224-255 Its very Simple Regards, Christian C Network Admin
(#16)
Darkest
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06-03-2017, 02:47 | posts: 10,044

Quote:
 Originally Posted by ManYou You are using Class C ip address 192.168.10/24 address 6 bit for host means you have 2^6 - 2 =64 host ip address in a subnet your subnet is 255.255.255.192 so your subnet range is 0-63,64-127,128-191,192-255. every subnet first IP is network ID and last Ip is broadcast ID. so 192.168.10.0 is subnet id of first subnet 192.168.10.63 is broadcast id of first network suppose if your subnetmask is 255.255.255.224 Total number of host ip in one subnet 2^5-2=30 subnet range=0-31,32-63,64-95,...224-255 Its very Simple Regards, Christian C Network Admin
Apparently checking dates and user status isn't.

This thread was posted back in 2015 by a member who has since been banned. I'm not sure why you felt the need to sign up to the forum specifically for this.

Last edited by Darkest; 06-03-2017 at 02:49.

 (#17) scatman839 Ancient Guru     Videocard: 7970m/970 Mini, KD55XD800 Processor: i7 3610QM/i5 6500 Mainboard: HM77/B150M-C Memory: 12GB D3/16GB D4 Soundcard: Via HD, x-530 PSU: 180w/RM650x 06-03-2017, 16:23 | posts: 13,143 | Location: Scotland I'm amazed how little I remember of even of subnetting after 2 years of not doing anything networking.
 (#18) allesclar Ancient Guru     Videocard: Nvidia GeForce GT 540M Processor: Intel Core i7 2670QM Mainboard: Samsung BA92-07584A Memory: Corsair 16GB DDR3 1333MHz Soundcard: Onboard PSU: N/A 06-04-2017, 22:36 | posts: 5,350 | Location: England haha jesus was a good few years ago i wrote that too
 (#19) Ryu5uzaku Ancient Guru     Videocard: 980ti gaming 1490/7700 Processor: 1800x 3.92ghz 1.3 v Mainboard: Asus CH VI x370 Memory: 16GB 3ghz ddr4 Soundcard: Asus strix pro PSU: 850W SF platinum 06-05-2017, 11:17 | posts: 6,639 | Location: Finland All this reminds me of the Cisco courses I did take. Oh god no... I could calculate these back then. Can't now because I've only been coding for past 6 years after school.

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