I need to design a network. I'm a newbie and going step-by-step. Let me briefly explain my little "project" to you: I'm designing a network to a company. This company has two offices at two distant cities and leased a serial line to connect these two. The network administrator is given an IP The network is needed to design to follow these specifications:

1- The company's headquarters should have two different sub-networks with 30 hosts capacity.

2- The branch office should have 14 hosts capacity.

3- The leased serial line should have 2 IP addresses.

4- The internet should be provided from the HQ.

5- A hardware firewall with no routing ability should be installed.

6- RIPv2 should be used.

Right now, I have learned how to use VLSM and given the IP addresses to the hosts. I guess now I should move into the physical topology, however I have no information about how to design such a network. Where to start, or where to look into for these information? Thanks for all your help.

  • is this a real or imaginary project? Jun 12, 2015 at 12:44
  • It is not real. I just started at a network company as an intern. They just want me to learn by myself but there is no resource for me to use.
    – Onur
    Jun 12, 2015 at 12:45
  • 1
    as phrased the problem is very ambiguous, I'm afraid you're better off asking in chat because you seem to need a conversation about the issues Jun 12, 2015 at 12:48
  • as for physical topology, draw 3 cirles. Inside each cricle, draw a smaller circle and a square and a line connecting them to one another. Then, title each large circle Hq, B1, B2. Draw a ligntning bolt between the circle in hq and each smaller circle in each branch. Finally, in Hq draw a second smaller square and outside the larger circle draw a cloud with a line connecting it to the second smaller box at Hq. draw a line connecting the 2nd smaller box at Hq to the 1st small box. Done. Jun 12, 2015 at 15:45
  • @MikePennington, I read this a bit differently. To me it seems the OP isn't asking how to design this particular topology, rather he is asking how to do network design more generally and where to find information on designing networks.
    – YLearn
    Jun 12, 2015 at 20:59

1 Answer 1


1) Two VLANs:

; /27 is 30 IPs, less one for the gw IP
vlan 20: (, reserved for future use in HQ or elsewhere)

2) Single network:

; /28 is 14 IPs, less one for the gw IP (1928.168.240-256)(unused, reserved for future expansion)

3) Point-to-Point link

HQ end:
Remote end:

4) Route Internet through HQ

HQ router redistributes in RIP to remote

5) Firewall

Install a firewall in bridged/transparent mode

6) RIPv2

HQ advertises and to Remote over PtP link
Remote advertises (expand to /27 if you use the expansion block) to HQ over serial link

Here's a quick and dirty physical map:

     inline fw
       router~~~~~ serial ptp ~~~~~ remote router
         |                               |
         |<- trunks vlan 10,20           |
         |                               |
         |                               |
     48port sw                    24 port sw, no vlans
     |       |
     |       |
     |       | <-vlan 10 access ports
     |<-vlan 20 access ports
  • While this is a good start at providing a topology for this situation, the OP wasn't asking for this topology and as such it doesn't actually address the OP's questions: How to design a physical topology? and I have no information about how to design such a network. Where to start, or where to look into for these information?
    – YLearn
    Jun 12, 2015 at 20:55
  • This individual has apparently been given a task designed to develop (or plumb) their understanding of netmasks. I'm not convinced we are giving the person or the employer any benefit by performing the task for them.
    – GeorgeB
    Jun 13, 2015 at 4:04
  • Although I've had an account on here for quite some time, I haven't used it until the last few weeks, so I'm just learning the ropes. Thanks for the feedback.
    – stevieb
    Jun 13, 2015 at 13:00

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