You want to create a standard access list that denies the subnet of the following host: 172.16.144.17/21. Which of the following would you start your list with?
Options
A. access-list 10 deny 172.16.48.0 255.255.240.0
B. access-list 10 deny 172.16.144.0 0.0.7.255
C. access-list 10 deny 172.16.64.0 0.0.31.255
D. access-list 10 deny 172.16.136.0 0.0.15.255
Correct Answer
access-list 10 deny 172.16.144.0 0.0.7.255
Explanation
First, you must know that a /21 is 255.255.248.0, which is a block size of 8 in the third octet. Counting by eight, this makes our subnet 144 in the third octet, and the wildcard for the third octet would be 7 since the wildcard is always one less than the block size.
More questions
1. How many collision domains are created when you segment a network with a 12-port switch?
You need 5 subnets, each with at least 16 hosts. The mask 255.255.255.240 provides 16 subnets with 14 hosts-this will not work. The mask 255.255.255.224 provides 8 subnets, each with 30 hosts. This is the best answer.
5. Which command is required for connectivity in a Frame Relay network if Inverse ARP is not operational?
If you have a router in your Frame Relay network that does not support IARP, you must create Frame Relay maps on your router, which provide known DLCI-to-IP address mappings.
6. What VTP mode allows you to change VLAN information on the switch?
A CIDR address of /19 is 255.255.224.0. This is a Class B address, so that is only 3 subnet bits, but it provides 13 host bits, or 8 subnets, each with 8,190 hosts.
8. Which command will allow you to see real-time translations on your router?
Any secondary route to a remote network is considered a feasible successor, and those routes are only found in the topology table and used as backup routes in case of primary route failure. You can see the topology table with the
show ip eigrp topology command.