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Network subnetting/design

I have asked a similar question before but I need a little more detail. I currently have a network on the 10.0.50.0/24 network (Location A) and we are adding a new location (location B). I need communications (Data/Phone) between the two locations (location A and location B) and I am trying to figure out the best network address to assign to the new location (location B). I would like to use the 10.0.0.0/21 network for the Location B then eventually change location A the 10.0.0.0/21 (all I will need to do is change the subnet mask) network.
Until I get Location A on the same network as Location B how do I route between the two? 10.0.0.0/21 overlaps 10.0.50.0/24 network. What is my best solution so the two locations can communicate and I can have the 10.0.0.0/21 network at location B and 10.0.50.0/24 at location A? I will need more than 254 IP addresses at location B and eventually location A so another /24 network will not work. If you have any questions please ask. Any help is appreciated. Check out the network list attached.

List-of-networks.doc

Justin Ellenbecker

Technically they do not overlap you are using a form of VLSM - Variable Length Subnet Masking. If you use 10.0.0.0/21 you will go to 10.0.7.254 from here your next network could be 10.0.8.0/24 and use all 24s all of the way up. So you should have no troubles. ISPs do this a lot when some customers need 16 addresses and some need 32. As long as you are not overlapping a used subnet. For example you could not use 10.0.48.0/21 and the 10.0.50.0/24 at the same time. Hope this helps.

StrifeJester

m203hcon

you cannot route between networks in the same segment 10.0.0.0/21 if you can't connect the networks via Ethernet thus needing fiber or VPN use following picture
siteA 10.0.50.0/21 - router - wan- router 10.0.58.0/21
if you can connect via ethernet and your site is 10.0.50.0/24 make B 10.0.51.0/24
make a default gateway 10.0.50.1 on site A and 10.0.51.1 on site b make a route in both
default gateway's so the 2 networks can see each other
than you can change the subnet mask from each client easily to /21 without any interrupt
you can take as long as you like to do this they will stay in touch
rgds
Harry

qbakies

Actually 10.0.0.0/21 doesn't overlap 10.0.50.0/24. Usable IPs for 10.0.0.0/21 are:

10.0.0.1 - 10.0.7.254

So you aren't going to have an issue with overlap or not being able to route traffic.

Lee W, MVP

Why such a huge subnet? Frankly, I don't like going above 254 nodes in a subnet. Maybe, if you really need, a /23, but a /21 is too many to me... are you that big a company that you need (have physical room for) 2000 systems on the same subnet AND you cannot afford a router to link subnets and keep your broadcast domains a reasonable size?

Just trying to understand and perhaps provide a different, more easily workable plan for you.

Justin Ellenbecker

What will be the connection between the sites? Will it be a leased line or VPN? Obviously if it is something like leased line you will need routers at each location and then you may want to use a /30 on your network just for the routers on each end. with cisco gear you can actually use a /31 and really save on IPs but I am personally not a fan of this yet. Then you would simply need to use a routing protocol such as EIGRP.

alg205

ASKER

I will have a 10 Mbps Metro Ethernet between sites.

alg205

ASKER

I am open to other suggestions. No we do not need a /21 network, I can go smaller, but I need more than 254 host per subnet and I need each location on its own subnet.

alg205

ASKER

Back to our connection between sites. To be more specific we will have a 10 Mbps Mtro Ethernet between sites with a VPN failover.

alg205

ASKER

Here is a list of Routers, switches, and firewalls we currently have.
3 Cisco 3750 Cat
1 Cisco 2611 Router
6 Cisco 2950 Cat

We are looking into purchasing
3 more 3750s
2 5510 ASAs
1 or 2 2811 routers

Justin Ellenbecker

Then you should be fine using the subnets you provided with a router somewhere or a layer 3 switch that can route the subnets until you have the chance to make the changes. If you do have layer three switching then i would look into possibly breakign the subnets down if possible and segmenting your traffic to reduce broadcast traffic.

Justin Ellenbecker

I would use the ASAs to do the failover easily and the 3750s are perfect with the Layer 3 and using vlans to help segment the traffic

alg205

ASKER

StrifeJester will you be more specific please? Thanks

Justin Ellenbecker

for example we use VLANs here to keep all of our servers separate from our workstations and all of the routers to other facilities are in their own vlan as well. You can use the 3750s to create these VLANs then the VLANs have their own IP and you points the machines at the VLAN IP for the defualt gateway. You then use a routing protocol or static routes to tell the traffic what goes where. With the intervlan routing being handled by the 3750s themselves you will not need to program routes for these.

Justin Ellenbecker

How does your topology look? We break things up like this as an example: Printers, Servers, Workstations, Backup Network, Routers, VOIP, etc. We use all cisco phones and call manager so our voice and data are separate vlans and the switch can then prioritize the voice traffic on a port as well.

alg205

ASKER

StrifeJester,
We have everything on the 10.0.50.0/network, but we have switches on 10.0.50.1-10, routers 11- 20, servers, 21-40 and so on. I have been wanting to setup or topology like yours is though. I have used VLANs at other companys I have worked for but here it has never been in place, but I think I will be imoplementing VLANS.

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Justin Ellenbecker

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alg205

ASKER

Thanks, You have been very helpful and I like the VLAN ideas. It all makes since now, but I do need to read up on VLSM. In my test environment I have 10.0.54.0/23 talking to 10.0.50.0/24 and rip enabled for the Sonicwall and router. I want to use EIGRP so I am looking into purchasing ASAs so everything will talk EIGRP.