Question about Network Design

Radiant9

Question for you all. As a part of my studying for the CCNA test (30 days away and counting) I have decided to build a reasonable sized network in Packet Tracer. Basically this network has 4 routers (each a pretend office in a different city) all connected via Serial. Each "Office" has 6 switches. S1 hangs off the router. S1 connects to S2 and S3. S2 connects to S4 and S5. S3 connects to S5 and S6. This office also has 4 PCs representing 4 divisions. PC1 is the IT department and hangs off S1. PC2 hangs off S4 and is for the Exec dept. PC3 hangs off S5 and is for Sales. PC4 hangs off S6 and is for Production.

OK, now that you're nice and confused (I can send you my saved Packet Tracer if it helps you "see" it), my question;

I have gotten decent at Subnetting. Now I'm finding that I don't fully understand what needs to have a network. In my design, I assume each "City" (Each Router and attached switches/PCs) will have it's own base network. Each division (PCs) will have their own subnet that coincides with their VLAN. OK, I believe I understand that. What I'm unsure about is mostly the switches. Each FA port will have it's own address (right?), but is the space between each switch connection considered it's own network?

I hope I'm being clear enough. I know this is somewhat of a large, detailed question. I appreciate your time. This addressing of networks is confusing for me. If it would help, I can send you my packet tracer save or I can draw up the network in Vizio for you.

Anyways, thanks in advance!

hermeszdata

Radiant9 wrote: »

Each FA port will have it's own address (right?), but is the space between each switch connection considered it's own network?

Based on the above, I would recommend re-visiting the chapter(s) on switches and switching as it is clear you have not mastered this material. One must have a sound understanding of a switch's purpose within the network topology, how they work (OSI Layer of operation, data unit type - frame forwarding), VLAN operation, and how to manage them!

Generally, we apply ip addresses to end-point devices, devices we need to access remotely to monitor or configure, and routable interfaces (Router LAN/WAN interfaces). Switches are L2 devices and as such cannot route information (L3 capable switches can but this is beyond CCNA scope).

I do not mean to come across as being harsh, but I would strongly advise pushing back your "30 days away and counting" exam date as it is clear that you have not mastered the material which is the foundation for every other networking topic you will be tested on. Unless of course you have money to throw away!

okplaya

You probably should attach the file.

Are you trying to practice anything in particular, or simply building a large network?

Radiant9

Hermez,

You didn't come across as harsh. My explanation was limited based on the fact that building an entire network is a large, detailed undertaking. I understand that switches work on L2. I understand VLANs and am currently installing them on this network. I just couldn't remember if I needed to assign IP addys to the switch interfaces. You're right. Switches are L2, don't need L3 IP addressing. Should have been obvious to me. Right now my brain is full of 1s, 0s, rules, powers of 2s, etc. Sometimes I forget the obvious. Thank you.

okplaya,

The main point of me putting this network together is to take all this book knowledge and put it to a practical use. It helps me retain it better. This network has routing, switching, VLANs, vtp, stp, subnetting and addressing, etc.

I'll put the file in my dropbox and post the link in a few.

Thanks again.

Radiant9

OK, so as I get deeper into this network I am (luckily) finding my weak spots. I knew I had remembered having to address switches when I was in class. What needs to be addressed in the switches is the management VLANs. That's not as complex as thinking I had to address each port, and shouldn't be a problem.

I have a question for you all though. So in this network, each router has 6 switches (Cisco 2960s) connected directly/indirectly to it. As I am setting up the VLANS I am noticing that VTP has auto-setup itself and that each switch is set as a VTP server. I figure this is unnecessary and so on the first group I set up 1 switch as the server and set the rest to client mode. Suddenly the activity on this network (judging by the blinking lights in Packet Tracer) shot up CONSIDERABLY compared to the groups all set to server. Why is this and is it a problem?

BTW, still workin on getting the lab into my dropbox.

Radiant9

I keep having questions, then as I go further I find the answer. Sorry if I'm spamming you guys with this, but it's really helping my learning/retention process.

So a funny thing happened. I put packet tracer into Sim mode and the group that I had changed all switches but 1 to VTP client mode was, sure enough, spamming broadcasts. So I went into one of the switches and turned on vtp debugging, just to see, and it crashed my PC. LOL! So I went back into my Cisco labs book while my PC was rebooting and, lo and behold, VTP pruning is there for just this exact reason. Ah ha! Guarantee I'll pass any VTP questions that come up in the test.

darkerz

Radiant9 wrote: »

I keep having questions, then as I go further I find the answer. Sorry if I'm spamming you guys with this, but it's really helping my learning/retention process.

So a funny thing happened. I put packet tracer into Sim mode and the group that I had changed all switches but 1 to VTP client mode was, sure enough, spamming broadcasts. So I went into one of the switches and turned on vtp debugging, just to see, and it crashed my PC. LOL! So I went back into my Cisco labs book while my PC was rebooting and, lo and behold, VTP pruning is there for just this exact reason. Ah ha! Guarantee I'll pass any VTP questions that come up in the test.

Now imagine having a real lab.

I'm on day 3 and I feel like the months in packet tracer were a lie.

Radiant9

No kidding. In fact, VTP Pruning doesn't work in Packet Tracer when your designing your own network from scratch. It works in a couple "pre-configured" scenarios, but that's it....

Luckily I got about 20 hours in class with my hands on real cisco routers/switches.

Besides, right now the goal is to pass the test. Once that's done and I get an actual networking job, then I'll worry myself about what was misleading in packet tracer. 1 thing at a time.

Radiant9

If you have Packet Tracer, you can download my save of this Network in my public dropbox. The file should be here.

It's by no means finished, nor even functional yet. Feel free to play around with it or whatever.

billyr

Just a couple of things on STP:

By default Cisco switches are already set to the Server mode.
Only the Server switch can create or delete a Vlan.
The Server, Client and Transparent mode switch can all send VTP updates but only the Server and Client will update their database with the new info.
When it comes to the matter of which switch will update the other, it does not matter if you are the Server or Client, whoever has the highest revision number will win.
If you have the VTP domain name set but no password then as soon as a new switch is added and a trunk is formed then the new switch will pick up the domain name.

If the VTP domain name is set but no password and a rogue switch is added to your network with a higher revision number - it will not, repeat not update all your switches and replace your VLANs with it's own as I read in so many books. As the rogue switch forms a trunk with your network it will pick up the new domain name, this resets its own revision number back to zero, as it's now at zero the higher revision numbers of your own switch will now overwrite the rogue switches database. The only way a rogue switch would wipe out your Vlans would be if it had the exact same domain name as your own and a higher revision number.

Radiant9

Hey guys. I have a (probably dumb) question in regards to this network I am designing. Hope you all can help.

I am starting to assign IP addys to the network and I'm getting a little confused about subnetting/VLSM. In this network I have 4 "branch offices". Each branch has 4 VLANs. VLAN99 for Management/IT. Vlan10 for Executive. Vlan20 for Sales. Vlan30 for Production. I want to assign the most effective subnets for each group, but I'm confusing myself. Let's use my "NY Branch" as an example.

The NY branch has a class B net of 172.16.0.0
IT needs 100 available hosts (including management ports for switches/router)
Exec needs 760 Hosts
Sales - 640
Prod - 350

Now the way I am trying to do this is like this;
IT 172.16.99.* /25
Exec 172.16.10.* /22
Sales 172.16.20.* /22
Prod 172.16.30.* /23

Should this work? It seems like it would, but I'm concerned my VLSM/Subnetting understanding is weak here and I don't want to configure this entire network wrong.

Thanks in Advance.

Met44

Radiant9 wrote: »

It seems like it would, but I'm concerned my VLSM/Subnetting understanding is weak here and I don't want to configure this entire network wrong.

Well, it is either right, or it is wrong. How would someone figure out if an acceptable mask is being used? You came up with the masks to begin with, so go over your work (figure out the answers again from scratch) and you should come up with a definitive answer -- that, or you will find the exact spot at which your understanding becomes fuzzy.

In the case of the latter, post back how you're coming up with the answers and someone will help.

hermeszdata

Radiant9 wrote: »

Hey guys. I have a (probably dumb) question in regards to this network I am designing. Hope you all can help.

I am starting to assign IP addys to the network and I'm getting a little confused about subnetting/VLSM. In this network I have 4 "branch offices". Each branch has 4 VLANs. VLAN99 for Management/IT. Vlan10 for Executive. Vlan20 for Sales. Vlan30 for Production. I want to assign the most effective subnets for each group, but I'm confusing myself. Let's use my "NY Branch" as an example.

The NY branch has a class B net of 172.16.0.0
IT needs 100 available hosts (including management ports for switches/router)
Exec needs 760 Hosts
Sales - 640
Prod - 350

Now the way I am trying to do this is like this;
IT 172.16.99.* /25
Exec 172.16.10.* /22
Sales 172.16.20.* /22
Prod 172.16.30.* /23

Should this work? It seems like it would, but I'm concerned my VLSM/Subnetting understanding is weak here and I don't want to configure this entire network wrong.

Thanks in Advance.

Did you actually sit down and write the address ranges to see how they related to each other?

I.E - Exec network is in the middle of the 172.16.8.0/22 block of addresses.

Is there a particular reason you chose the network number as you did.

What about:
Exec - 172.16.0.0/22
Sales - 172.16.4.0/22
Prod - 172.16.8.0/23
IT - 172.16.255.128/25

VLSM is really about efficiently using the available address space. Not a big deal when using the Private IP space but very important it a company has an entire Class B block!

Radiant9

I appreciate the responses. I figured it was me being thick.

I have FINISHED! WOOHOO! My entire network runs and is entirely functional! This was a really helpful way to study and put the knowledge into practical use. I feel pretty confident now about the lab sections of the test.

If you would like to check this network out, you can download it from my dropbox folder.

Hermez, I changed my addressing. To simplify I used 172.16.x.x /24 for my internal networks. Vlan 10 is 172.16.10.x, vlan 20 is 172.16.20.x, etc. The subinterfaces on the router start the hosts on each network (i.e. SubInt for Vlan10 is int fa0/0.10 172.16.10.1 255.255.255.0, etc). The management vlan (vlan99) for each switch starts at 11 (i.e. S3's would be 172.16.99.13 /24). And the PCs start at 100 (i.e. Sales PC1 is on Vlan20 and so would be 172.16.20.100 /24). This way everything is somewhat organized and easy to remember. I know it's not entirely accurate. If I have 400 hosts in the sales dept then I wouldn't be able to start at 172.16.20.100 /24 as that would only give me 153 hosts. But I figure as long as I understand that, it makes little difference.

I practiced more subnetting within my networks between routers. I had 4 routers connected. Each router had 2 serial ports connected, so I needed 4 networks, each only needed 2 hosts, so I used a /30 (i.e. 216.10.62.1 /30 is Ser 0/2/0 on the first router and 216.10.62.2 /30 for Ser 0/2/1).

Anyways, again, thanks SO much for everyone's help! I learned a lot and solidified a lot more. Hope some of you chose to follow this example as an extra way of study. Hand's on is REAL helpful for me.