因此，cisco 路由器允许使用通配符掩码来指定 ACL。通配符掩码使用 32 位长整数指定一组主机，但它们与典型的网络掩码不同之处在于，当通配符掩码中的某个位为 0 时，它表示强制匹配，当它为 1 时，它是通配符。有些人（甚至是 cisco）称它为反向掩码，事实是所有网络掩码都可以通过简单的反转转换为通配符掩码，但反之则不行。因为您可以使用如下所示的通配符掩码：
0.0.255.0 0.0.255.254 0.255.0.254 等等。
确实没有等效的网络掩码
我想做的（并希望有人已经做过这样的事情）是将通用通配符转换为等效 CIDR 块的集合。如果解决方案在 Python 中会非常好（即输出生成臭名昭著的 netaddr IPNetwork 对象），但如果你真的只有一个有效的算法来解决这个问题，我会接受。
在 Python 2.7 中：
import ipaddress
mask = u"0.1.2.7"
address = u"172.18.161.2"
def wildcard_mask_test (test_octet, acl_octet, acl_wildcard_octet):
#Test one number against acl address and mask
#Bitwise OR of test_octet and acl_octet against the octet of the wildcard mask
test_result = test_octet | acl_wildcard_octet
acl_result = acl_octet | acl_wildcard_octet
#Return value is whether they match
return (acl_result == test_result)
def test_octet (acl_octet, acl_wildcard_octet):
matches = []
#Test all possible numbers in an octet (0..255) against octet of acl and mask
#Short circuit here for a mask value of 0 since it matches only the $acl_octet
if (acl_wildcard_octet == 0):
matches.append(acl_octet)
return matches
else:
for test_octet in range(0,256):
if (wildcard_mask_test(test_octet, acl_octet, acl_wildcard_octet)):
matches.append(test_octet)
return matches
def list_of_matches_acl (acl_address, acl_mask):
#Pass in the variables of ACL network and wildcard mask
#eg 10.200.128.0 0.0.0.255
potential_matches=[]
#Split the incoming parameters into 4 octets
acl_address_octets = acl_address.split('.')
for n in range(0,4):
acl_address_octets[n] = int(acl_address_octets[n])
acl_mask_octets = acl_mask.split('.')
for n in range(0,4):
acl_mask_octets[n] = int(acl_mask_octets[n])
#Test the 1st octet
matches_octet_1_ref = test_octet(acl_address_octets[0], acl_mask_octets[0])
#Test the 2nd octet
matches_octet_2_ref = test_octet(acl_address_octets[1], acl_mask_octets[1])
#Test the 3rd octet
matches_octet_3_ref = test_octet(acl_address_octets[2], acl_mask_octets[2])
#Test the 4th octet
matches_octet_4_ref = test_octet(acl_address_octets[3], acl_mask_octets[3])
#Assemble the list of possible matches
#Iterating over all options for each octet
for n1 in matches_octet_1_ref:
for n2 in matches_octet_2_ref:
for n3 in matches_octet_3_ref:
for n4 in matches_octet_4_ref:
potential_matches.append(str(n1)+'.'+str(n2)+'.'+str(n3)+'.'+str(n4))
ip = []
for m in potential_matches:
ip.append(ipaddress.ip_address(unicode(m)))
out = list(ipaddress.collapse_addresses(ip))
return out
a = list_of_matches_acl (address, mask)
print a
首先数一下你从右端有多少个连续的 1。这将决定 CIDR 块的大小。
每个剩余的通配符将使您拥有的 CIDR 块数增加一倍。
我很确定最常见的情况是“通配符掩码正是子网掩码的倒数”，而您的示例0.0.255.0并不典型。但是，我认为这会满足您的要求。使用 Python 3.3 的ipaddress 模块：
import ipaddress
mask = "0.0.255.0"
address = "172.18.161.1"
mask_int = int.from_bytes((ipaddress.IPv4Address(mask).packed), "big")
address_int = int.from_bytes(ipaddress.IPv4Address(address).packed, "big")
lower = ipaddress.IPv4Address((2 ** 32 - 1 - mask_int) & address_int)
upper = ipaddress.IPv4Address(mask_int | address_int)
subnet_range = list(ipaddress.summarize_address_range(lower, upper))
在示例中，我们将172.18.161.1用通配符替换第三个八位字节，即172.18.x.1x 的范围从 0 到 255。所以我们的范围将是172.18.0.1through 172.18.255.1。这些摘要块在subnet_range列表中：
172.18.0.1/32
172.18.0.2/31
172.18.0.4/30
172.18.0.8/29
172.18.0.16/28
172.18.0.32/27
172.18.0.64/26
172.18.0.128/25
172.18.1.0/24
172.18.2.0/23
172.18.4.0/22
172.18.8.0/21
172.18.16.0/20
172.18.32.0/19
172.18.64.0/18
172.18.128.0/18
172.18.192.0/19
172.18.224.0/20
172.18.240.0/21
172.18.248.0/22
172.18.252.0/23
172.18.254.0/24
172.18.255.0/31
我在尝试自己解决这个问题时遇到了这个问题，最后写了一些新的 perl 代码来解决这个问题，所以我想我会分享
它还没有优化或优雅（还），但它可以工作，并且应该非常清楚它在做什么。
list_of_matches('10.48.140.82' , '0.0.0.1')
返回：
10.48.140.82 10.48.140.83
和
list_of_matches('10.48.140.82' , '0.1.0.1')
返回：
10.48.140.82 10.48.140.83 10.49.140.82 10.49.140.83
和
list_of_matches('10.48.140.82' , '0.1.5.1')
返回：
10.48.136.82 10.48.136.83 10.48.137.82 10.48.137.83 10.48.140.82 10.48.140.83 10.48.141.82 10.48.141.83 10.49.136.82 10.49.136.83 10.49.137.82 10.49.137.83 10.49.140.82 10.49.140.83 10.49.141.82 10.49.141.83
代码：
sub list_of_matches_acl {
#Pass in the variables of ACL network and wildcard mask
#eg 10.200.128.0 0.0.0.255
my ( $acl_address, $acl_mask ) = @_;
#The array of possible matches
my @potential_matches;
#Split the incoming parameters into 4 octets
my @acl_address_octets = split /\./, $acl_address;
my @acl_mask_octets = split /\./, $acl_mask;
#Test the 1st octet
my $matches_octet_1_ref
= test_octet( $acl_address_octets[0], $acl_mask_octets[0] );
#Copy the referenced array into a new one
my @one = @{$matches_octet_1_ref};
#Test the 2nd octet
my $matches_octet_2_ref
= test_octet( $acl_address_octets[1], $acl_mask_octets[1] );
#Copy the referenced array into a new one
my @two = @{$matches_octet_2_ref};
#Test the 3rd octet
my $matches_octet_3_ref
= test_octet( $acl_address_octets[2], $acl_mask_octets[2] );
#Copy the referenced array into a new one
my @three = @{$matches_octet_3_ref};
#Test the 4th octet
my $matches_octet_4_ref
= test_octet( $acl_address_octets[3], $acl_mask_octets[3] );
#Copy the referenced array into a new one
my @four = @{$matches_octet_4_ref};
#Assemble the list of possible matches
#Iterating over all options for each octet
foreach my $octet1 (@one) {
foreach my $octet2 (@two) {
foreach my $octet3 (@three) {
foreach my $octet4 (@four) {
#Save this potential match to the array of matches
#say "$octet1.$octet2.$octet3.$octet4"
push( @potential_matches,
"$octet1.$octet2.$octet3.$octet4" );
}
}
}
}
return \@potential_matches;
}
sub test_octet {
#Test all possible numbers in an octet (0..255) against octet of acl and mask
my ( $acl_octet, $acl_wildcard_octet ) = @_;
my @matches;
#Short circuit here for a mask value of 0 since it matches only the $acl_octet
if ( $acl_wildcard_octet eq 0 ) {
push @matches, $acl_octet;
}
else {
for my $test_octet ( 0 .. 255 ) {
if (wildcard_mask_test(
$test_octet, $acl_octet, $acl_wildcard_octet
)
)
{
#If this value is a match, save it
push @matches, $test_octet;
}
}
}
#Return which values from 0..255 match
return \@matches;
}
sub wildcard_mask_test {
#Test one number against acl address and mask
my ( $test_octet, $acl_octet, $acl_wildcard_octet ) = @_;
#Bitwise OR of test_octet and acl_octet against the octet of the wildcard mask
my $test_result = $test_octet | $acl_wildcard_octet;
my $acl_result = $acl_octet | $acl_wildcard_octet;
#Return value is whether they match
return ( $acl_result eq $test_result );
}
Python 3 通用实现（v4 和 v6），使用内置的 ipaddress 模块：
import itertools
from ipaddress import NetmaskValueError
import ipaddress
MAX_DONT_CARE_BITS = 8
def acl_with_wildcard_to_netmasks(address_str: str, wildcard_str: str):
"""
Translates an ACL (address, wildcard) to a list of ip_network objects (address, netmask)
:param address_str: IP address string (v4 or v6)
:param wildcard_str: wildcard mask (v4 or v6)
:return: list of IP networks
E.G for address="172.18.161.2" and wildcard "0.1.2.7"
it returns:
[IPv4Network('172.18.161.0/29'), IPv4Network('172.18.163.0/29'),
IPv4Network('172.19.161.0/29'), IPv4Network('172.19.163.0/29')]
"""
ip_addr = ipaddress.ip_address(address_str)
wildcard = ipaddress.ip_address(wildcard_str)
if wildcard.version != ip_addr.version:
raise ValueError(f"IP version mismtach: address_str({address_str}), wildcard_str({wildcard_str})")
# default values for v4
_length = ipaddress.IPV4LENGTH
_net_cls = ipaddress.IPv4Network
if wildcard.version == 6:
# values for v6
_length = ipaddress.IPV6LENGTH
_net_cls = ipaddress.IPv6Network
mask_bits = [int(b) for b in format(int(wildcard), F"0{_length}b")]
# We keep count of zero bits position (left-most is 0)
dont_care_bits_index = [i for i, e in enumerate(reversed(mask_bits)) if e == 1]
# We count how many contiguous zeros are from left-most bit, and we will mask them with a netmask
hostmask_length = 0
for (pos, bit) in enumerate(dont_care_bits_index):
if pos != bit:
break
hostmask_length += 1
# We only keep the bits that can't be dealt with by a netmask and need to be expanded to cartesian product
dont_care_to_expand_index = dont_care_bits_index[hostmask_length:]
# reverse in order to have the final loop iterate last through high order bits
dont_care_to_expand_index.reverse()
if len(dont_care_to_expand_index) > MAX_DONT_CARE_BITS:
raise NetmaskValueError(f"{wildcard_str} contains more than {MAX_DONT_CARE_BITS} non-contiguous wildcard bits")
ip_int_original = int(ip_addr)
subnets = []
for bits_values in itertools.product((0,1), repeat=len(dont_care_to_expand_index)):
# enforce the bits_values in the IP address
ip_int = ip_int_original
for (index, val) in zip(dont_care_to_expand_index, bits_values):
sb_mask = 1 << index
if val:
ip_int |= sb_mask
else:
ip_int &= ~sb_mask
subnets.append(_net_cls((ip_int, _length-hostmask_length), strict=False))
return subnets
if __name__ == '__main__':
# IPv4
a4 = [ipaddress.IPv4Network('172.18.161.0/29'), ipaddress.IPv4Network('172.18.163.0/29'),
ipaddress.IPv4Network('172.19.161.0/29'), ipaddress.IPv4Network('172.19.163.0/29')]
b4 = acl_with_wildcard_to_netmasks('172.18.161.2', '0.1.2.7')
print(b4)
print(f"Lists are equal: {a4 == b4} (length {len(a4)})")
# IPv6
a6 = [ipaddress.IPv6Network('eed0:feff::/64'), ipaddress.IPv6Network('eed0:ffff::/64'),
ipaddress.IPv6Network('fed0:feff::/64'), ipaddress.IPv6Network('fed0:ffff::/64')]
b6 = acl_with_wildcard_to_netmasks('fed0:ffff::1', '1000:0100:0000:0000:ffff:ffff:ffff:ffff')
print(b6)
print(f"Lists are equal: {a6 == b6} (length {len(a6)})")
也许还可以评论一下这有什么用处：一个具体的用例是将通用 ACL（使用通配符语法）转换为瞻博网络 QFX10k 配置（硬件仅支持网络掩码）。