acl wildcard masks

nathan8nathan8 Posts: 12Member ■□□□□□□□□□
what wildcard mask would you use to specify the whole 192.168.6.0 /30 network.
I thought it would be 0.0.0.3 as a 30 bit subnet mask is 255.255.255.252
and 256 - 252 = 4 and it would be 1 less which is 3 so 0.0.0.3

Please help

nathan

Comments

  • marlon23marlon23 Posts: 164Member ■■□□□□□□□□
    192.168.6.0 255.255.255.252 is subnet-zero so be carefull about its usage. (#ip subnet-zero <-- global configuration mode command to enable it).

    Wildcard mas is correct 0.0.0.3, but the formula is little different. Calculation is "255.255.255.255 minus subnet-mask"

    so:
    255.255.255.255
    - - - -
    255.255.255.252
    = = = =
    0 . 0 . 0 . 3

    with this math you can cover whole subnet with wildcard mask, and its so easy and really fast.

    Hope this formula was clear to understand :)
    LAB: 7609-S, 7606-S, 10008, 2x 7301, 7204, 7201 + bunch of ISRs & CAT switches
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