Answers: IP Addresses 1

certskills
By certskills April 30, 2016 09:10

Try a little subnetting math for a quick review, and add some IP address configuration – short, sweet, and just one more quick round of practice. Check out the initial requirements in this post, and come back here for the answers.

Answers

Figure 1: Simple Hub and Spoke Topology

 

Example 1: Core Config

 

Example 2: Branch1 Config

 

Example 3: Branch2 Config

 

Example 4: Branch3 Config

 

Commentary

Every network engineer has to plan for and configure IP addresses, and that process includes calculating subnet IDs, the range of addresses in each subnet, and choosing the addresses to use for router interfaces. The configuration of the address and mask is pretty simple. For instance, the router command to configure an IP address for a specific interface is ip address ip-address subnet-mask, and is configured while inside interface configuration mode.

This lab tasks you with configuring the IP addresses for all of the router interfaces shown in the figure; the specific IP subnets have already been selected and are shown in this figure.

Note that you could configure the addresses in any order, but for the sake of discussion, this section works through the numbered requirements (1, 2, and 3) in order.

First, on the Core router, that router has three interfaces connecting to the Branches. The interface connecting to ‘Branch1’ is the GigabitEthernet0/1 interface which has been assigned to the 172.16.1.200/29 subnet. That subnet includes usable IP addresses 172.16.1.201 through 172.16.1.206, so the highest useable IP address in this subnet is 172.16.1.206. The mask in DDN notation is 255.255.255.248, which is the equivalent of /29.

Continuing the discussion of router Core, the interface connecting to ‘Branch2’ is the GigabitEthernet0/2 interface which has been assigned to the 172.16.1.192/29 subnet; the highest useable IP address in this subnet is 172.16.1.198 using a subnet mask of 255.255.255.248. Finally, the interface connecting to ‘Branch3’ is the GigabitEthernet0/3 interface which has been assigned to the 172.16.1.208/29 subnet; the highest useable IP address in this subnet is 172.16.1.214 using a subnet mask of 255.255.255.248.

Requirement number 2 asks us to configure the branch router interfaces on the links that connect to the core router. The above discussion has already detailed the subnets, so all you have to do is pick the highest remaining IP address. Table 1 lists the addresses used on both the Core router and on the Branch router on the other end of each link.

Link Subnet Core Address Branch Address
Core to Branch1 172.16.1.200/29 172.16.1.206 172.16.1.205
Core to Branch2 172.16.1.192/29 172.16.1.198 172.16.1.197
Core to Branch3 172.16.1.208/29 172.16.1.214 172.16.1.213

Table 1: WAN Subnets and Address Assignments

 

Finally, for requirement 3, you need to calculate the range of addresses in three more subnets, and use the highest address for the router interface IP addresses. Table 2 lists those details.

Link Subnet First Usable Address Last Usable Address (Router Address)
Branch1 172.16.1.0/26 172.16.1.1 172.16.1.62
Branch2 172.16.1.64/26 172.16.1.65 172.16.1.126
Branch3 172.16.1.128/26 172.16.1.129 172.16.1.190

Table 2: Branch LAN Subnet Analysis

 

Once you complete all the calculations, the task is simple: configure the ip address commands as listed in Examples 1, 2, 3, and 4.

IP Addresses 1
Login Security 1
certskills
By certskills April 30, 2016 09:10
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2 Comments

  1. JAMES December 28, 07:06

    Hello Wendell,

    I definitely will have to keep practicing, this one took me;
    9 minutes and 33 seconds to complete.

    Best Regards,
    James Watson

    Reply to this comment
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