Hi Alef, Which part is getting you confused?
One of the most important things to be aware of is that a wildcard mask is not just an inverted network mask. A rule regarding netmasks is that when looking at it as a binary sequence it has to be a bunch of consecutive 1s and 0s, as soon as the first 0 appears, the following digits must continue to be 0 For a wild card mask, the above concept does not apply, 1s and 0s can be in any order. The binary sequence of the wild card mask has a meaning that a 0 means, the value of this bit much match, where a 1 means, I don't care what the source value is and is therefore an implied match. To give a simple example, say you are in OSPF and have an interface 192.168.1.1/24 that you wish to enable. You could be most specific and do router ospf 1 network 192.168.1.1 0.0.0.0 area 0 or more general and do router ospf 1 network 192.168.1.0 0.0.0.255 area 0 I guess you could just go directly to the interface and do "ip ospf 1 area 0" but that kind of sidelines the use case here, so lets ignore that for the time being :) in both cases OSPF would be enabled for the interface, however if you wanted to have the most direct control, specifying the complete address and using an exact wildcard mask ensures that only that interface gets activated. For example if I renumbered the interface on 192.168.1.1/24 to 192.168.1.111/24in the first case OSPF would be disabled for the interface and the later it would not since the IP still matches the wildcard mask. There are also interesting things you can do with ACLs to match multiple non-consecutive IP addresses by use of an interesting wildcard mask, these rely on a base IP address and a wildcard string that relies on must match/don't care values for the binary string. Is that of any help? Cheers, Adam On Thu, Jun 2, 2011 at 7:22 AM, Alef <[email protected]> wrote: > Does anyone have any recommendations for a good tutorial on wildcard masks? > I know the one on the ipexpert site, i'm afraid i need some more material to > digest if possible ;-) > i'm somewhere in between getting it and not getting it i think > thanks, > alef > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
