| Subnet Mask |
CIDR |
Net Bits |
Host Bits |
# of Nets |
Hosts/Net |
Total Hosts |
| 255.255.0.0 |
/16 |
0 |
16 |
1 |
65534 |
65534 |
| 255.255.128.0 |
/17 |
1 |
15 |
0(2*) |
32766 |
0(65534*) |
| 255.255.192.0 |
/18 |
2 |
14 |
2(4*) |
16382 |
32764(65528*) |
| 255.255.224.0 |
/19 |
3 |
13 |
6(8*) |
8190 |
49140(65520*) |
| 255.255.240.0 |
/20 |
4 |
12 |
14(16*) |
4094 |
57316(65504*) |
| 255.255.248.0 |
/21 |
5 |
11 |
30(32*) |
2046 |
61380(65472*) |
| 255.255.252.0 |
/22 |
6 |
10 |
62(64*) |
1022 |
63364(65408*) |
| 255.255.254.0 |
/23 |
7 |
9 |
126(128*) |
510 |
64260(65280*) |
| 255.255.255.0 |
/24 |
8 |
8 |
254(256*) |
254 |
64516(65024*) |
| 255.255.255.128 |
/25 |
9 |
7 |
510(512*) |
126 |
64260(64512*) |
| 255.255.255.192 |
/26 |
10 |
6 |
1022(1024*) |
62 |
63364(63488*) |
| 255.255.255.224 |
/27 |
11 |
5 |
2046(2048*) |
30 |
61380(61440*) |
| 255.255.255.240 |
/28 |
12 |
4 |
4094(4096*) |
14 |
57316(57344*) |
| 255.255.255.248 |
/29 |
13 |
3 |
8190(8192*) |
6 |
49140(49152*) |
| 255.255.255.252 |
/30 |
14 |
2 |
16382(16384*) |
2 |
32764(32768*) |
| 255.255.255.254 |
/31 |
15 |
1 |
32766(32768*) |
0* |
0(32768**) |
| 255.255.255.255 |
/32 |
16 |
0 |
65534(65536*) |
1*** |
65534(65536*) |
[*] According to classic IP routing rules you are not able to use the subnets with all zeros or ones in the network portion. However most modern machines have no trouble actually using the upper and lower subnets. Steven C. Jensen has a very good discussion of lower/upper subnet use , including notes on how to convince Cisco routers to do it. (I’m not sure this applies for /32 though….)
[**] Note that you should not use a host address with all zeros as that means this host in many IP implementations (and is considered the broadcast address in some antiquated systems [SunOS-2?]), and neither can you use a host address with all ones, as that’s the broadcast address for the subnet. The host address of all zeros, in combination with the network address, are also used to specify the complete subnet address (RFC 1105).
This means that a 31-bit netmask is essentially useless since it leaves only two addresses per net: one for the network number, and the other for the broadcast address. In theory though you could specify a host address as the same as the network address if the IP implementation of the host(s) in question does not map an all-zeros host number to be equivalent to the localhost. I wouldn’t advise this though unless you’re really strapped for subnets. It’s far safer and more general to use /30 nets instead.
[***] An all-one’s netmask (i.e. all 32 bits) specifies a host address.
Example:
Valid subnets on a network 172.16.0.0/18 (i.e. with a subnet mask of 255.255.192.0) are:
Subnet 1: 172.16.64.0 with addresses 172.16.64.1 -> 172.16.100.254
Subnet 2: 197.16.128.0 with addresses 172.16.128.1 -> 172.16.128.254
Tired of being attacked by foreign countries? Here is some useful network assignment information so you can configure your IDS and Firewall against them. Simply block ANY and ALL traffic from network ranges to be safe! Be careful not to block your own neighborhood, unless you really mean to. The list is not complete, but I’ll add updates as I find them. Continue reading IP Addresses & Network Reservations For Firewall & IDS Filtration
I just got this update from a friend, and I must say that Microsoft sure wants to keep their hand in our pockets. What makes less sense, is why SO many people continue to use Microsoft products when almost everything is available in Open Source for free without limitations. I think that Ubuntu rocks and it’s a GREAT alternative to paying fees to minimizers like Microsoft.If you want to spend money, give it to developers who have your best software interests at heart, not the corporate monster who lists their top 10 directives as getting your money, then list number 11 as development.
LMAO. Heaven forbid I get more of an OS than what I need. I can be assured that will never be the case with Microsoft:
“On Tuesday, Microsoft was granted US Patent No. 7,536,726 (it was filed in 2005) for intentionally crippling the functionality of an operating system by ‘making selected portions and functionality of the operating system unavailable to the user or by limiting the user’s ability to add software applications or device drivers to the computer’ until an ‘agreed upon sum of money’ is paid to ‘unlock or otherwise make available the restricted functionality.’ According to Microsoft, this solves a ‘problem inherent in open architecture systems,’ i.e., ‘they are generally licensed with complete use rights and/or functionality that may be beyond the need or desire of the system purchaser.’ An additional problem with open architecture systems, Microsoft explains, is that ‘virtually anyone can write an application that can be executed on the system.’ Nice to see the USPTO rewarding Microsoft’s eight problem-solving inventors, including Linux killer (and antelope killer) Joachim Kempin, who’s been credited withgetting Microsoft hauled into federal court on antitrust charges.”
This article was posted by mac Hacker at Blogspot, and explains how to get your Norton Antivirus subscription to continue past its expiration date. So, when that annoying subscription window pops up and you ask yourself, “How would I make the subscription reset itself?” you can do it yourself. The PHP Kemist does not recommend you evade your obligation to pay for software and subscriptions, and this article is for the Mac hackers who are curious. Continue reading How To Reset The Subscription For Norton Antivirus Version 11
Secure Code Auditing is a structured approach to identifying, evaluating and mitigating programming and database security risks to web applications, databases and general network security. The majority of programmers are not security-minded, let alone security experts. Applications and infrastructure are typically designed with security vulnerabilities that can lead to security exploitations and potentially catastrophic results for your servers, network, and your business overall. When the programming team lacks security expertise and experience, and where security vulnerabilities may be an important issue for your business, a subsequent secure code audit is required. Different security consulting companies approach secure code audits differently, but essentially have the same goals in mind. This article is my description of what a secure code audit is, how we approach code inspection, and how to balance the factors that influence secure code audits. Continue reading What Is A Secure Code Audit And Do I Need One?
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The following is a scam email to beware of. It is invalid and should be ignored!
Greetings,
My name is Mrs. Fardiya zaini, I am a dying woman who had decided to donate what I have to the Charities.
I am 49 years old and was diagnosed for cancer about two years ago, immediately after the death of my husband.
I have been touched to donate from what I have inherited from my late husband for the good work of allah, rather
than allow his relatives to use my husband’s hard earned fund. Continue reading My name is Mrs. Fardiya zaini
