Terry is right, I may have jumped the gun with the inverse mask statement (although it's mentioned this way in many documents). For Terry's experiment let's assume we want to match the voice vlan for buildings 20 and 30 (10.20.4.0 and 10.30.4.0). By breaking this down into binary and using AND/OR logic we can easily come up with our answer
00001010.00010100.00000100.0000000 00001010.00011110.00000100.0000000 ---------------------------------- 00001010.00010100.00000100.0000000 = 10.20.4.0 00001010.00010100.00000100.0000000 00001010.00011110.00000100.0000000 ---------------------------------- 00000000.00001010.00000000.0000000 = 0.10.0.0 So the "wildcard" mask to match both buildings would be 0.10.0.0 Cheers! Thank you. Steve Di Bias Network Engineer - Information Systems Valley Health System - Las Vegas Office - 702- 369-7594 Cell - 702-241-1801 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Terry Slattery Sent: Monday, April 11, 2011 6:58 PM To: Jay Taylor Cc: <[email protected]> Subject: Re: [OSL | CCIE_RS] offset-list and wild card mask Good answer, Jay. For everyone who thinks that the wild-card mask is the opposite of the subnet mask... I have a set of subnets that I need to match. The first octet is 10. The second octet is a building number. The third octet identifies the subnet in each building, and is "4" for the voice subnet, which is what I want to match. Build a wild-card mask that matches 10.x.4.x Is it the inverse of the subnet mask? -tcs On 7/22/64 2:59 PM, Jay Taylor wrote: > Offset list is used to increment the metric of certain routes. > > In a wildcard mask a binary 0 means the bit must match and a binary 1 > means it does not have to match. This is reverse logic compared to a > normal subnet mask. Also, unlike a subnet mask the 1's and 0's do not > need to be contiguous. > > > On Mon, Apr 11, 2011 at 11:04 AM, Uli<[email protected]> wrote: > >> Hi Expert, >> >> Does anyone can explain to me about offset-list as I kind of confused >> with it. also, in my opinion that wild card mask is reverse of subnet >> mask, but someone told me it isn't ? >> >> >> Regards >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, >> please visit www.ipexpert.com >> > > > -- Terry Slattery CCIE# 1026 _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com UHS Confidentiality Notice: This e-mail message, including any attachments, is for the sole use of the intended recipient (s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution of this information is prohibited. If this was sent to you in error, please notify the sender by reply e-mail and destroy all copies of the original message. _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
