Great, detailed explanation ! Thanks!
Brett Michael Spunt Internetworking Engineer CCNP,MCSE,CIPT,CCNA,MCP,CNA,A+ 818 734-6880 ext.59 [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Haakon Claassen (hclaasse) Sent: Sunday, September 29, 2002 1:28 PM To: [EMAIL PROTECTED] Subject: RE: Filter odd routes via wildcard bits - How?? [7:54496] Hi Just do the binary calculus 0.0.254.255 is 0000 0000. 0000 0000. 1111 1110 . 1111 1111 apply that to your prefix 172.168.1.0 the first two bytes (172 and 168) will have to match and the last bit of the 3rd byte needs to be 1 so that would be 172.168.1 .3 .5 .7 .8 in the other case .0 .2 .4 .6 you have a 0 at that position These maches the routes to be denied (the odd ones) And the even gets permitted by the permit any In short subnet masks need to be contiguous 1 ones followed by contiguous zeros wildcards don't 1010 0111 . 1111 0000 . 1110 0111 . 1010 1010 is a valid wildcard ( 167.240.199.170) regs Haakon Claassen EMEA - IT Transport Services -WAN Cisco Systems De Kleetlaan 6b - Pegasus Park B-1831 Diegem (Belgium) -----Original Message----- From: Cisco Nuts [mailto:[EMAIL PROTECTED]] Sent: zondag 29 september 2002 20:59 To: [EMAIL PROTECTED] Subject: Filter odd routes via wildcard bits - How?? [7:54496] Hello, I am trying to understand how a wildcard mask of 0.0.254.255 filters odd routes so that only even routes get across the router. Ex. If you have routes for 172.168.1.0/24, 2.0/24, 3.0/24, 4.0/24, 5.0/24, 6.0/24 and you have an access-list of: #access-list 11 deny 172.168.1.0 0.0.254.255 #access-list 11 permit any And a: #distribute-list 11 out This will allow only: 172.168.2.0/24, 4.0/24 and 6.0/24 routes out. Anyone can kindly explain the magic of this 0.0.254.255 wildcard? Thank you. Sincerely. BTW: Anyone know the link on this on CCO? _________________________________________________________________ Send and receive Hotmail on your mobile device: http://mobile.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54504&t=54496 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
