Cisco based network - VLAN's

[RichardParry]

I am setting up a server colocation setup, consisting currently of the following cisco devices;

1. Cisco 5000, with Supervisor II module & ISL capable switch blade
2. Cisco 1924-EN
3. Cisco 3620 w/ NM-1FE-FX (for uplink to the Sup II) & NM-1FE-TX (for connectivity to my ISP.

I have successfully setup a test configuration, with the 5000 running as a VTP server and the 1924 as a VTP client, and using a private IP range, I have been able to get an ISL trunk between the 1924 and 5000 and an ISL trunk between the 5000 and the 3620's NM module for InterVLAN routing. This is working great, using different IP ranges (such as 192.168.1.1 on VLAN 1 and 192.168.2.1 on VLAN 2). But when I put the setup into the live environment, I will be assigned a full Class C netblock (255 IP's) and I would want to assign VLAN's to certain block's. For example I dont want one single VLAN of 254 IP's, as this would be a nightmare to manage and a potential issue with regards to broadcast storms, security etc. What would be the best way to subnet/vlan my class c netblock into smaller VLAN's, of say 10's IP's per subnet? (what is your suggestion on the number of IP's I should have per subnet?)

Hope this makes sense! Thanx !!

 

[RichardParry]

Edit, that should read "..... number of IP's I should have per VLAN?

 

[vipergg]

To tell you the truth we run a major corp and we use almost all vlans with 254 users in each . Broadcast storms aren't generally an issue . If you want smaller chunks just adjust the mask to make it fit the number users you want on each . For example on a class C if you want 64 users use 255.255.255.192. If you want a good little subnet calc go to

http://www.wildpackets.com/products/ipsubnetcalculator

, its free .

 

[vipergg]

Just as added comment after reading your post again , you don't need to break the vlans down to that small a size , that is overkill . Honestly in a network that size you really don't need more than 2 subnets unless you want to add an extra one to keep all your servers on one . Remember anything that is not on the same vlan must be routed , you certainly don't want to be routing 14 different vlans on 3620 . The less routing you have to do the faster your network will be and the less overhead on the router .

 

[RichardParry]

Okies, I think what I will do is stick with a single VLAN for the moment, and then when customers (as I will be offering colo) want a netblock, I will subnet a chunk for them and put it into another VLAN for just their use.... The 10 IP's per vlan was just an example, it would be a bit crazy since I would wasting a lot of IP's for use as netaddr/broadcast in that scenario....