A cool trick with wildcard masks !

kaynaankaynaan Member Posts: 30 ■■□□□□□□□□
when prepariing 4 any exam i get so scared.. i read anything i can get my handz on... this has a downside. once in a while u get some really good stuff. maybe an easier way around a complex problem, a small trick that saves u alot of time... but u just dont remember where u read it ???. i found this cool trick 4 wild card masks but i have no idea where i read it, if any of u know about it plz give me a source, or add something...
enough with the small talk. letz get to the nitty gritty .....

when doing wildcard masks for ACL,indentifying interesting traffic for DDR,NAT etc. usually u see wildcard masks like these :

- (host)
- (class A network)
- (class B network)
- (Class C network)
** all subnets in class C **
- subnet)
- subnet)
- subnet)
- (any)

but now lets assume, u'r making a pool of ip addresses for dynamic NAT. configurations and u want to identify ip address (only 14 addresses). using the above mentioned wildcard masks only allow u to specify blocks of 4,8,16,32,64,128 etc.

1- write the upper range, and the bottom range ontop of each other.
2-all matching bits equal '0' any non matching bits equal '1' ( (

0. 0.0.00010010 (

u'll find the wild card mask '' will only allow ip address through

if any one knowz an easy way around some particularly tough calculations , or a simpler way of memorising hard to remember facts plz share .....
God give me the serenity to accept the things that i cannot change...and the courage to change the things i can....and the wisdom to know the difference.


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