从IP范围转换为CIDR掩码 [英] Conversion from IP Range to CIDR Mask
问题描述
我一直在研究一种算法,用于将IP范围转换为CIDR表示法中的列表IP(此后将作为元组提及)。
现在,让我感到困惑的是弄清楚这个转换的最坏情况场景是什么;
I've been working on an algorithm for converting an IP Range to a list IPs in CIDR Notation (will be mentioned as tuples henceforth). Now, what puzzles me is figuring out what is the Worst Case Scenario for this conversion;
IPv4可以获得的最大元组数是多少范围?
我可以获得IPv6范围的最大元组数是多少?
如何计算?erp
What is the maximum number of tuples I can get for an IPv4 Range? What is the maximum number of tuples I can get for an IPv6 Range? How was this calculated?erp
我正在使用修改后的C版本(不是递归的)以下Python脚本:
I'm using a modified C version (which is not recursive) of the following Python script:
1 #!/usr/bin/env python
2
3 import sys
4 import re
5
6 def ip2int(ip) :
7 ret = 0
8 match = re.match("(\d*)\.(\d*)\.(\d*)\.(\d*)", ip)
9 if not match : return 0
10 for i in xrange(4) : ret = (ret << 8) + int(match.groups()[i])
11 return ret
12
13 def int2ip(ipnum) :
14 ip1 = ipnum >> 24
15 ip2 = ipnum >> 16 & 0xFF
16 ip3 = ipnum >> 8 & 0xFF
17 ip4 = ipnum & 0xFF
18 return "%d.%d.%d.%d" % (ip1, ip2, ip3, ip4)
19
20 def printrange(startip, endip) :
21 bits = 1
22 mask = 1
23 while bits < 32 :
24 newip = startip | mask
25 if (newip>endip) or (((startip>>bits) << bits) != startip) :
26 bits = bits - 1
27 mask = mask >> 1
28 break
29 bits = bits + 1
30 mask = (mask<<1) + 1
31 newip = startip | mask
32 bits = 32 - bits
33 print "%s/%d" % (int2ip(startip), bits)
34 if newip < endip :
35 printrange(newip + 1, endip)
36
37 while 1 :
38 line = sys.stdin.readline().strip()
39 if not line : break
40 chars = line.split(" ")
41 print "#%s - %s" % (chars[0], chars[1])
42 ip1 = ip2int(chars[0])
43 ip2 = ip2int(chars[1])
44 printrange(ip1, ip2)
推荐答案
这只是猜测,但似乎是,单个IPv4范围内CIDR前缀的最大数量是62(32 * 2) - 2),对于IPv6 - 254(128 * 2 - 2)。
It is just guess, but seems to be, that maximum number for CIDR prefixes in single IPv4 range is 62 (32*2 - 2), and for IPv6 - 254 (128*2 - 2).
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