To match the first set 10.1.32.2 0.0.3.0 and to add the other router 10.1.32.2 0.0.3.1
-Marc On Wed, Apr 13, 2011 at 7:43 AM, Terry Slattery <[email protected]> wrote: > Steve, > > I thought that you might have hit 'send' a bit too quickly. But it gave me a > great opportunity to continue the thread to show what happens as you try to > match other things - in this case matching all hosts in each subnet or > matching all subnets in the second octet. > > Your example would be good for matching specific subnets in a routing table, > where the last octet would be '0'. My example is better for matching devices > in an ACL. > > As a continuation of the exercise, and to make sure everyone understands > wildcard masks, let's create a more real-world scenario, similar to what you > might find on a CCIE exam. > > Task: Configure OSPF on a router with four interfaces: > 10.1.32.2/24 > 10.1.33.2/24 > 10.1.34.2/24 > 10.1.35.2/24 > > What wildcard mask will match only those interfaces in a single OSPF network > configuration statement? > > Now let's say that there's an adjacent router and you're configuring HSRP > between them. How would the network statement have to change for use in the > adjacent router that uses the .3 host address (i.e. 10.1.32.3/24)? > > Is there a wildcard mask that will work for both routers, so that you have > an ospf configuration that can be shared between the two routers? > > You can't arrive at the right answer to the above by inverting the subnet > mask. > > I'll may have to write about this subject in a blog post... especially since > my quick Google search came up with so much inaccurate information on the > subject. > > -tcs > > On 4/12/11 9:38 PM, Di Bias, Steve wrote: >> >> Terry I realized that I put a zero there after I hit send, I just didn't >> send another email correcting myself. The point I was making was that you >> were correct, and I was attempting to show that with the wildcard mask. >> >> //s >> >> Terry Slattery<[email protected]> wrote: >> >> >> Steve, >> >> That matches the 10.20.4.0 subnet and 10.30.4.0 subnet, but it won't match >> any >> hosts on either subnet, because the last octet is 0 and the wild-card bits >> are >> zero (must match). >> >> I was looking for a wildcard mask of 0.10.0.255 to match all hosts on >> either subnet. >> >> If you went further, you could have also come up with 0.255.0.255, to >> match >> 10.x.4.x. >> >> -tcs >> >> On 4/12/11 12:15 AM, Di Bias, Steve wrote: >>> >>> 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 >> >> >> >> 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. > > -- > Terry Slattery CCIE# 1026 > > _______________________________________________ > 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
