10-22-2001 02:27 AM - edited 02-20-2020 09:16 PM
my route has following configuration:
access-list 1 permit 0.0.0.0
access-list 1 permit 131.108.0.0 0.0.15.255
access-list 1 deny 1.1.0.0 255.255.255.255
I can't understand what's mean of these.
my question is :
1.access-list 1 permit 0.0.0.0 permit what range of ip address.
2.access-list 1 permit 131.108.0.0 0.0.15.255 permit what range of ip address.
thank you!
10-22-2001 08:50 AM
permit 0.0.0.0 has no mask, so it permits just that: 0.0.0.0 (0.0.0.0 to 0.0.0.0 is the range)
(permit 0.0.0.0 is equivalent to permit 0.0.0.0 0.0.0.0 - all bits must match to pass.)
Note that you would only use 0.0.0.0 for filtering routes, not traffic, because the range only includes the default which would only be used as a route, never as a source or destination address in a packet.
permit 131.108.0.0 0.0.15.255 has a wild card mask ("don't care" bits) which can be analyzed in binary:
00000000.00000000.00001111.11111111
10000011.01101110.00000000.00000000
This indicates a range of:
10000011.01101110.00000000.00000000 to 10000011.01101110.00001111.11111111
which translates into decimal:
131.108.0.0 to 131.108.15.255
It would be a little more complicated to visualize if you had a subnet like this:
permit 131.108.48.0 0.0.15.255
Again in binary:
00000000.00000000.00001111.11111111
10000011.01101110.00110000.00000000
This indicates a range of:
10000011.01101110.00110000.00000000 to 10000011.01101110.00111111.11111111
which translates to decimal:
131.108.48.0 - 131.108.63.255
Hope this helps,
Mark
10-22-2001 06:56 PM
Thank for your reply.It solved my question.
10-26-2001 02:44 AM
I hate to disagree with you but 0.0.0.0 is used as a source address when a PC sends out a DHCP request. The source address is 0.0.0.0 and the destination is 255.255.255.255. I agree with everything else though.
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