setting up WAN and LAN network

Hello, I am trying to assign IP addresses to this network, however I am having trouble interpreting the instructions. The instructions are:
1. use 172.26.0.0/16 for internal addressing with IP subnet zero enabled
2. Apply /30 subnets for all serial interfaces. Use the last available subnet.
3. Assign an appropriately sized subnet for the DHCP pool on the Taupo LAN, which requires 550 hosts.
4. Assign an appropriately sized subnet for Waihi LAN which requires 200 hosts.
5. Assign appropriately sized subnets for the three VLANS connected to Huntly. VLAN 15(Sales) requires 100 hosts, VLAN 25 (Engineering) requires 70 hosts and VLAN 86 (Management and native) requires 12 hosts. Router-on-a-stick will also be implemented using 802.1Q trunking.
6. Assign addresses to the PCs in the Waihi LAN and Huntly VLANs. The PCs in the Taupo LAN will obtain their addresses via DHCP.

My main problem is I am unsure what addresses to assign the /30 serial interfaces. As per #2 above it says use the last subnet available ? Can someone please help with that ? Thanks kindly for any input.

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Comments

pogue

I don't think you should get too tied up with what exactly the "last subnet" means. It is a poorly written objective.

You start with a 172.16.0.0/16 network, so the last class C network would be 172.16.255.0/24. The absolute last possible subnet would be 172.16.255.252/30.

In the end, it does not really matter. As long as you know how to accurately assess how many subnets you need, and can properly subnet a larger network range down to your individual /30s, you're fine.

Furthermore, if the objective is asking you to use one class C or subportion of a class C across all your point-to-point links, I would argue this is bad network design, as you will not be able to summarize these networks properly in order to reduce the size of all the routing tables.

Russ

macattacker

thanks for that.
Can I just ask regarding the 4 routers and their serial interfaces. I would not be able to use subnets from my allocated address 172.26.0.0 anyway ? Because they are external links, so I would have use another address entirely eg. 10.0.0.0 etc.
Am I correct ?
Therfore I just dont understand at all what the instructions mean by "Apply /30 subnets for all serial interfaces. USE THE LAST AVAILABLE SUBNET."
Thanks for any help.

pogue

I don't understand what you are saying.. "External" links have no bearing on whether or not you can choose subnets from your currently allocated network.

Are you studying for the CCNP or the CCNA? Taking a network and subnetting it to allocate to multiple network links within your organization is a basic CCNA task that you should be comfortable with before starting CCNP level studies.

Russ

macattacker

sorry, I should have posted in CCNA rather than this group.
I just want to know if, based on the instructions given, I should be using subnets from the address 172.26.0.0 to address the serial interfaces of my four routers using /30 subnets.
i.e would the three routers in the OSPF area be regarded as internal addressing ?
Thank you kindly for any advice.

pogue

macattacker wrote: »

i.e would the three routers in the OSPF area be regarded as internal addressing ?

mac,

"Internal" addresses are a concept related to NAT and are far beyond what you are being tested on in this lab. You were given 172.16.0.0/16 to use, don't make up other concepts to confuse yourself. Do exactly what the lab tells you to. Subnet the class B network you were given and put a separate subnet on each network.

Please don't take offense, but is English your primary language? If not, do you have a CCNA guide that is in your native language? You are mentioning concepts like "internal" addresses that really don't have anything at all to do with what you are being told to do in the lab.

Russ