Access list

[The_guroo_2]

i have a genral question abt wild card mask.....like if we wanna allow or deny a whole class we write 210.54.8.0 0.0.0.255 but some time we use 210.54.8.0 0.0.0.0........like both thing r same so in which scenario we will use all o's and in which scenarios we will use 255.........at he last....thanks in advance

[royalblues]

Hi shahryar

The theory behind the access-list wild cards mask is : 0 is considered to be exact match and

1 is considered to be a wild card or dont care

so in the ablove example 210.54.8.0 0.0.0.255 the last octet is all 1s and hence represent dont care bits. i.e match the first 3 octets exactly while ignoring the 4th octet

but if you have 210.54.8.0 0.0.0.0 configured,it is asking it to match all the 4 octets exactly which would basically mean to match a single host.

(actually cisco converts the mask 0.0.0.0 as host and 255.255.255.255 as any)

HTH

Narayan