EIGRP/VSLM Help

Hi all!

I've been giving a practice PT file to do with EIGRP and VSLM and I'm sure I'm missing out on a fundamental step or approach when it comes to assigning values to interfaces.

The file at hand can be found at EIGRP Practice Updated.pka

I understand that the Melbourne network is a /27, Brisbane a /26 and Sydney a /28 and that the f0/0 interfaces will have corresponding addresses (172.0.0.1 /26 for Sydney) but where I'm completely stuck is when it comes to the f0/0 and s0/0 interfaces.

For example when I go into the Melbourne router to configure the f0/1 interface I can only think of configuring it with 172.16.0.1 /27 as it is requires to be configured from the 1st address but it asks the same for the f0/0 interface and so I get an overlap.

Also I'm not too weary on where to apply the VSLM, from my understanding the summary route would be:

S. 11111111.11111111.11111111.11110000

B 11111111.11111111.11111111.11000000 because the bit disparity begins there

M 11111111.11111111.11111111.11100000

Any help lovingly appreciated.

Love, Grack.

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Comments

instant000

I'm not allowed to view that site from work, I apologize, but I know this much.

/26, block size is 64

/27, block size is 32
/28, block size is 16

In this case (and if these networks are contiguous) you could possibly summarize them with a 128 block size, which would mean using a /25

Without knowing the addesses (can't view them from this network), I am truly guessing.

Hope this helps.

EDIT: Saw you had an addressing overlapp. That's an easy one. Use an address that not's already in use. If you took the first address already, use the next one. You can't use the same address twice in the same subnet, and not expect to get problems. (Of course, there are exceptions to this, but those exceptions were designed for this purpose ... scenarios like multiple servers behind the same virtual IP, or IPV6 anycast come to mind.)

grackfields

Heyo thanks for that!

So far I've understood how to work out the PC IP/SNM and configure the f0/0 interfaces correctly but I still am unsure of what IP/Networks to assign to the f0/1 interfaces.

Any help would be loved!

--Grack

okplaya

I'm unable to see the file at the moment as well, but keep in mind that you have to follow subnetting rules. Could you provide the IP address and subnet mask you have assigned to each interface?

grackfields

http://i.imgur.com/0Rfyf.jpg

Hope that helps out thanks!

--Grack

okplaya

I think you're misunderstanding the question. You're on the right track, and you still have some addresses that can be used. Some questions for you....without VLAN's, if all devices connect to a switch can they be in the same broadcast domain? If so, can they be on the same subnet?

jwashington1981

A few things from your question and your diagram.

All four of the Fa 0/1 interfaces on the routers that are attached to the switch in the middle are going to need to be on the same subnet. You have a total of four interfaces so the next block up from 4 is 8 which gives you 6 usable addresses which will be enough to cover that. You will not need to use a /27. That's a waste of addresses.

Also, in the diagram, it says you will need to use a wildcard mask to advertise the EIGRP routes. That is incorrect. The only routing protocol that you're going to learn about for CCNA studies that you need the wildcard for is for OSPF. And later you'll use the wildcard mask again when you learn about ACLs. As far as EIGRP goes, when you use the no auto-summary command, that will cause EIGRP to go from using classful networks to classless and will find all of your subnets.

The summary route needs to be placed on Tokyo's S 0/0/1 interface exiting out towards Perth.

The way I learned VLSM is that you should always start with your largest block and work your way down to your smallest block to avoid any chance of overlapping.

If you have anymore questions, please let us know.

grackfields

Oh my god it's so much clearer now!

I gave the f0/1 interfaces a /29 and assigned them their designated address number and voila! Addresses configured!

Now now it's just a matter of working out how to advertise the routes with eigrp!

So much thanks:)

grackfields

Actually just looked at the check results tab to see if I had the f0/1 interfaces set with the right IPs and I don't

4 host addresses are needed for the routers connected to the switch in the middle so I need a /29.

Melbourne f0/1 uses the first address: 172.16.0.227 /29 (1st address)
f0/1 Perth: 172.16.0.228 /29
f0/1 Sydney: 172.16.0.229 /29
f0/1 Brisbane: 172.16.0.230 /29

These addresses seem to be wrong but I don't understand how

jwashington1981

They're not right because with a /29, the subnet address should be 172.16.0.224. The first address would be .225 instead of .227