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jskfan
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understanding Prefix-List

I am trying to understand he usage of Prefix-List , but it seems like they are abit complex.
for instance:

1***what is this saying:
ip prefix-list test seq 12 permit 192.168.1.0/16 ge 24 le 24
is it permitting 1902.168.0.0 all the way 192.168.1.0 ?

2***what is this saying:
ip prefix-list test seq 12 permit 192.168.1.0/16 le 32
is it permitting anything that starts with 192.168.X.X all the way 192.18.254.254 ?

3*** what about this, doe s it need "le" or "ge"
0.0.0.0/0

4*** what about these:
0.0.0.0/0 le 32
0.0.0.0/32


Thank you
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jskfan

8/22/2022 - Mon
SOLUTION
lruiz52

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jskfan

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Can you please check my post above and tell me if I am understanding it the right way or wrong way ?
thanks
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harbor235

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pergr

It is important to note that the prefix-list is use for matching prefixes (routes) and not individual IP addresses.
jskfan

ASKER
sorry I did not get it
ip prefix-list test seq 12 permit 192.168.1.0/16 ge 24 le 24
so /16 is meaningless since it will pass only subnets with 24 bits ?

I see you mention 25 bits .... I did not get get it...
since the condition says greater or equal 24 and less or equal 24...which means to me just 24
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rwheeler23
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jskfan

ASKER
I initially understood:
it will take : 192.168.1.0 to 192.168.254.0

Until I saw this, I extracted this from the pdf link given to me above:

ip prefix-list mylist seq 10 permit 172.16.0.0/16 ge 24 le 26
This will take the entire class B network 172.16.0.0 (172.16.0.0/16) and
pass only subnets with a /24, /25 or /26 mask (ge 24 le 26). So the exact
network 172.16.0.0/16 would actually fail the list because it does not have
a mask of /24, /25 or /26.
jskfan

ASKER
very complex, hard to understand it..
pergr

Correct.
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jskfan

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Thank you Guys!