Last Updated on July 31, 2021 by Admin 1
Click the Exhibit(s) button to view an EIGRP network. The partial output of the show running-config command on the rtrB router is as follows:
Which of the following subnets are blocked through the Fa0/0 interface of rtrB while sending updates to rtrC? (Choose all that apply.)
The 126.96.36.199/24, 188.8.131.52/25 and 184.108.40.206/30 subnets are blocked through the Fa0/0 interface of rtrB while sending updates to rtrC. The following lines in the output create an IP prefix list named blk_A:
ip prefix-list blk_A deny 220.127.116.11/16 ge 24 le 30
ip prefix-list blk_A permit 0.0.0.0/0 le 32
The blk_A list blocks the subnets that exactly match the first 16 most significant bits as 18.104.22.168. The ge keyword indicate that the subnet mask for the 22.214.171.124 subnets must be greater than or equal to 24 bits. Similarly, the le keyword indicates that the mask for the 126.96.36.199 subnets should be less than or equal to 30 bits. Therefore, all subnets of 188.8.131.52 network with masks 24, 25, 26, 27, 28, 29, and 30 are blocked.
The second line permits all other routes to be passed on. The subnets that match the blk_A prefix list are 184.108.40.206/24, 220.127.116.11/25, 18.104.22.168/30, and 22.214.171.124/28.
The line distribute-list prefix blk_A out indicates that the distribute-list command applies the blk_A prefix list to all the outgoing interfaces. This implies that if rtrB receives an update about the 126.96.36.199/24, 188.8.131.52/25, 184.108.40.206/30 or 220.127.116.11/28 subnets, they are blocked. In this case, the 18.104.22.168/28 is not blocked through the Fa0/0 interface to rtrC because it is directly connected.
The 22.214.171.124/18 and 126.96.36.199/22 subnets are not blocked through the Fa0/0 interface of rtrB to rtrC. This is because both these subnets are outside the range of prefix masks 24 through 30; hence, these two subnets are allowed through the Fa0/0 interface.
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