Implementing VLANs - going from class B to C on local LAN

[nunzeo]

We are a class B network with 10 different sites connected via Cisco routers.

10.1.x.x gateway is 10.1.1.1
10.2.x.x gateway is 10.2.1.1
10.3.x.x gateway is 10.3.1.1
10.4.x.x gateway is 10.4.1.1
Etc

Then each site (LAN) we have our servers, printers and clients on different subnets but still a class B

Example
Clients = 10.1.2.x/16 gateway = 10.1.1.1
Servers = 10.1.3.x/16 gateway = 10.1.1.1
Printers = 10.1.4.x/16 gateway = 10.1.1.1

I am looking to change all LANs to class C implement VLANs by putting in a layer 3 switch but I want to keep our WAN routers IP schemes the same.

Example
Clients = 10.1.2.x/24 gateway = 10.1.2.1
Servers = 10.1.3.x/24 gateway = 10.1.3.1
Printers = 10.1.4.x/24 gateway = 10.1.4.1
Then I guess I would put a default route for the next hop for all other traffic to our WAN router 10.1.1.1??

My question is, is it possible to do what I propose? And is it also possible to setup the VLANs on the layer 3 switch, trunk the ports, assigned the ports to specific VLANs all without messing up communication and then going back to the clients and servers and changing their subnet masks and gateways?

I hope I explained clearly enough.

Thanks.

 

[cisconooblet]

You need a different ip scheme than what you put in your examples. You need to use different subnets rather than what you have shown. They overlap. I personally would want to change the WAN scheme you are using. If I read it right your using a full class b for each wan link. A /30 subnet would be great here. Then come up with a scheme for your lans that does not overlap with any other lan/wan.

CCNA
Network +

 

[nunzeo]

thanks for the response but i guess i did not explain correctly. i guess you think they overlap because i said each site is configured as shown:

Clients = 10.1.2.x/16 gateway = 10.1.1.1
Servers = 10.1.3.x/16 gateway = 10.1.1.1
Printers = 10.1.4.x/16 gateway = 10.1.1.1

that was just an example of one site. site b would be 10.2.2.x/16 for clients and site c would be 10.3.2.x/16 for clients and so on.

so would it be possible to switch the local LANs to a class C from B and use inter-vlan technology and keep our WAN scheme the same?

 

[blueshark101]

Aren't they /24 ranges rather than /16...
10.1.2.x/16 is in fact 10.1.x.x/16
10.1.2.x/24 is 10.1.2.0 to 10.1.2.255
Essentially each site is a single /16 range split into a number of /24 subnets (VLANS). For each subnet you require you will need a VLAN interface (address) on your L3 device... That device will then route automatically between the subnets.

Can you do that... Yes it should not be a problem.

Can you migrate from one scheme to the other without impacting the systems ...? that might me more of a challenge!


-Blue
The significant problems we face cannot be solved at the same level of thinking we were at when we created them

 

[unclerico]

Changing things over from a /16 to multiple /24's and implementing a L3 switch with VLANs will be extremely simple. One thing that is guaranteed is that there will be some down time. Also, are you running a routing protocol or using static routes??

I hate all Uppercase... I don't want my groups to seem angry at me all the time! =)
- ColdFlame (vbscript forum)

 

[burtsbees]

Yes---the vlans will have a /24 mask and the default routes/static routes/routing protocol networks will all have the same /16. Basically, you would be summarizing with routes, acl's and/or route maps...

/

tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!

 

[cisconooblet]

I took what you said as running your point to point wans on a 10.1.x.x /16 subnet. (hopefully thats not the case)

I guess thats not what you meant. If you were that would be an overlap which is what I was getting at. The rest would be pretty easy to get done as stated above.

CCNA
Network +

 

[nunzeo]

Blueshark101,

Actually they are /16. I was just explaining how our client/servers are in different ranges but the same masks.

Cisconooblet,

I’m still confused on how they overlap. Site A is 10.1.x.x/16 and site B is 10.2.x.x/16 and so on.

Thanks for all the responses. I have plenty of hardware available so I guess the best way would be to setup somewhat of a duplicate network and test.

Thanks again. Nunzeo

 

[blueshark101]

No problem... I was assuming there was some logical separation but you're obviously just using the ranges for convinience only...

As stated by everyone, what you are proposing is quite standard, and straightforward to setup. So the answer is still yes!

-Blue
The significant problems we face cannot be solved at the same level of thinking we were at when we created them

 

[nunzeo]

After reading all of the posts and some research I did online I am somewhat confused. I am posting some examples here to reiterate my scenario.

Site A Router (10.1.1.1)
10.1.X.X/16

A Servers are:
10.1.3.0 range with a subnet of 255.255.0.0
A Clients are:
10.1.2.0 range with a subnet of 255.255.0.0

Site B Router (10.2.1.1)
10.2.X.X/16

B Servers are:
10.2.3.0 range with a subnet of 255.255.0.0
B Clients are:
10.2.2.0 range with a subnet of 255.255.0.0

Now I want to put in a layer 3 switch and implement VLANs behind each router as such.

Site A
Servers would stay on the 10.1.3.0 range but would go to a subnet mask of 255.255.255.0 and a GW of 10.1.3.1

Site B
Servers would stay on the 10.2.3.0 range but would go to a subnet mask of 255.255.255.0 and a GW of 10.2.3.1

Etc.

Now is it possible to do what I propose? Can I keep the router’s IP/Subnets the same but break down the subnets into class C behind them? So in other words can I keep Site A router as the 10.1.X.X/16 (GW 10.1.1.1) and then create all vlans as class C on the layer 3 switch that is directly connected to that router? If that is the case do I put a route on the L3 switch to send all traffic destined for 10.2.0.0 to the 10.1.1.1 router to find its next hop? From what I’ve read I can’t have a class C subnet sitting behind a class B because the class C is a part of B.

I inherited this network and its IP scheme and I want to clean it up as much as possible and limit the number of broadcasts.

Thanks for everyone’s help.

 

[blueshark101]

OK once more... Yes you can.


Your router will have a /24 interface on the 10.1.1.1 network but a /16 route on it for the 10.1.0.0 network via your L3 device. Your L3 should have interfaces to all the 10.1.x.0/24 networks so does not need routes defining - as it has connected interfaces. Finally, yes you need a route on the L3 device for the 10.2.0.0/16 network via 10.1.1.1.



-Blue
The significant problems we face cannot be solved at the same level of thinking we were at when we created them