Awesome. Thanks Tyson. It is clear now. Thanks, Vince Mashburn HP Americas Technology Services Account Services Manager FedEx On-site Office Phone: 901-263-6498 Mobile: 901-569-9734
-----Original Message----- From: Tyson Scott [mailto:[email protected]] Sent: Tuesday, February 09, 2010 7:58 AM To: Mashburn, Vince; [email protected] Subject: RE: [OSL | CCIE_RS] Advanced ACL filtering Vince, let's say you have 172.16.18.0/24 172.16.82.0/24 As you can see there are only two variants in the third octet. 18 and 82. Binary for these two numbers is 00010010 01010010 We can easily see that there is only one bit difference between the two numbers, the 64 bit. As a shortcut seeing that 18 and 82 are the only difference in the networks above I could do 82-18 = 64. 64 is a power of 2 and it is a bit boundary. So by subtracting the two I quickly get my network and mask without taking it to binary. The network is the lowest common denominator, 18; and mask is the sum or 64. Regards, Tyson Scott - CCIE #13513 R&S, Security, and SP Technical Instructor - IPexpert, Inc. Mailto: [email protected] Telephone: +1.810.326.1444, ext. 208 Live Assistance, Please visit: www.ipexpert.com/chat eFax: +1.810.454.0130 IPexpert is a premier provider of Classroom and Self-Study Cisco CCNA (R&S, Voice & Security), CCNP, CCVP, CCSP and CCIE (R&S, Voice, Security & Service Provider) Certification Training with locations throughout the United States, Europe and Australia. Be sure to check out our online communities at www.ipexpert.com/communities and our public website at www.ipexpert.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mashburn, Vince Sent: Tuesday, February 09, 2010 7:18 AM To: [email protected] Subject: [OSL | CCIE_RS] Advanced ACL filtering Question on ACL filtering with binary operations. When referring to the following shortcut: With seemingly random numbers, if only two variants per octet, sibtract the values. If the answer is a power of 2, then only 1 bit in the ACL is different. Can you clarify what "two variants per octet" is? Does it refer to the number of 1's in the mask or the number of bits different in the network? Also, when subtracting the two values, is that in decimal or binary? Vince Mashburn Sent from my Windows Mobile phone _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
