IPv4 Addresses 4

By certskills August 7, 2014 09:05

Practice makes memory. So, time for some practice with IPv4 address configuration on routers. This post is a traditional Config Lab exercise: you start with a network diagram and some planned IPv4 subnets. Your job: do some subletting math and configure the router interfaces with the correct IPv4 addresses and masks.



This lab asks you to configure all the router IP addresses for the design shown in Figure 1, given a set of requirements. At this point, do not configure static routes or a routing protocol; just configure the IP addresses per the following specific instructions:

  1. Use the subnets as listed in Figure 1.
  2. Routers must use the lowest IP address(es) in each subnet.
  3. If more than one router exists in a subnet, the router with the lower number in the hostname gets the lower IPv4 address. EG, R1 would have a lower IPv4 address than R2.
  4. Hosts should use the lowest IPv4 address in the subnet, with the same tiebreaker concept as stated in #3.

Figure 1: Router Triangle with IPv4 Subnets

Table 1 shows a way to organize the addresses for reference.

Table 1: IPv4 Addresses

Location Address/Mask
R1 G0/0
R1 G0/1
R1 G0/4
R2 G0/0
R2 G0/1
R2 G0/4
R3 G0/0
R3 G0/1
R3 G0/4


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Answers: IPv4 Addresses 4
By certskills August 7, 2014 09:05
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  1. Tanu March 6, 04:28

    I have a doubt in, /23, /23

    3rd is interesting. We should have Network Id changing in 3rd octet and not fourth octet. Please confirm

    Reply to this comment
    • CCENTSkills March 8, 11:29

      I agree, if you were finding lots of subnet IDs based on a /23 mask, the 3rd octet of those subnet IDs would be incremented, not the 4th octet. However, this exercise is to choose IP addresses from the subnets listed in the figure. So, at most, you would need to find the list of usable IP addresses in each subnet, and pick the lowest numbers (per the lab requirements).
      Or I could be totally missing your point. 🙂

      Reply to this comment
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