ccna security pdf 2018

ccna security pdf 2018.7.2.6 Performing SummarizationAs mentioned earlier, to summarize route entries, the first few digits of those route entries must be the same. In other words, both the first network number and the number of networks to be summarized must be an act of 2 (e.g., 2, 4, 8, 16, etc.) or an integer multiple thereof. For example, suppose the network number is 4 (which is a curtain of 2) and the integer multiples of this value are 4, 8, 12, 16, so using the correct subnet mask you can aggregate networks 4, 5, 6, and 7.The first network number must be a multiple of 2 depending on the aggregate subnet mask used. For example, when using the subnet mask 255.255.255.240 for aggregation, the first network number must be an integer multiple of 16 (the number of addresses contained in the subnet created using subnet mask/28). For example, 192.168.1.16/28 is a legal aggregation, while 192.168.1.8/28 is not (because its starting position is not an integer multiple of 16) If you wantThe number of networks that are aggregated is not a curtain of 2 or an integer multiple thereof, they can sometimes be aggregated into a series of smaller routes. curtain of 2 is 0, 2, 4, 8, 16, 32, 64, and 128. In addition, when performing aggregation, you must ensure that all routes being aggregated are associated with the router that advertises the aggregated route (located behind that router) o1. aggregation and 2's overlookWhen aggregating don't forget that the starting position must be a curtain of 2 or an integer multiple thereof. The trick to aggregation is to keep in mind the number of addresses corresponding to the various subnet mask values (0, 128, 192, 224, 240, 248, 252, 254, and 255 ), as shown in Table 7.3. For example, suppose there are two Class C subnets: 192.168.1.0/30 and 192.168.1.4/30, which contain a total of eight addresses, and the first address is a curtain of two (0), so they can be aggregated as 192.168.1.0/29, which contains the addresses 192.168.1.0 ~192.168.1.7.In looking at an example. Suppose there are two Class C subnets: 192.168.1.64/26 and 192.168.1.128/26, both of which contain 64 addresses, for a total of 128 addresses. For Class C networks, the subnet mask that provides 128 addresses is 255.255.255.128 (/25). However, this subnet mask poses a problem because the starting location is not a multiple of 128. With subnet mask /25, there are only two subnets: 192.168.1.0/25 and 192.168.1.128/25, but subnet 192.168.1.64/26 is on the first subnet, while subnet 192.168.1.128/26 is on the second subnet. Therefore, even though these two subnets are connected, you cannot use subnet mask /25 (255.255.255.128) to aggregate them. You can use subnet mask /24 (255.255.255.0) to summarize, but this will contain 256 addresses, not just the 128 addresses to be summarized.Table 7.3 Summarizing Network NumbersFor those new to subnetting and aggregation, these can be very confusing. Aggregation is nothing more than listing all the routes, finding the same number of bits at the beginning of those routes to identify the aggregated routes to be advertised, and making sure that routes that are not listed are excluded. Often, aggregation becomes difficult only when the initial addressing scheme (such as you might encounter on a CCNA exam) is just plain bad. In short, another IJ forgets that it is only possible to create a summary route when the total number of addresses is a curtain of 2. If it is not a storm of 2, the addresses must be grouped together and then aggregated separately.In the case of the CCNA exam, this is all that is required. 1. list all subnet numbers according to the network schematic, including subnets that are not connected to the current router. 2. Find out how many bits are the same at the beginning of the routes to be summarized; this is easily done using an icon similar to that in Table 7.1. 3. Create as many summarized routes as possible. 4. Announce each of the remaining routes separately.