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Need help on a 3550 routing/subnetting

I am looking on subnetting our colo class-C for security and performance reasons, here is our scenario.

One class-C address space, call it

subnet mask is

our providers gateway router is

Connected to our provider, we have a

48-port Cisco 3550 switch running 12.1.22-EA6 (ED) EMI IOS


All of our hosts are servers and will need to have public IPs from our class-C

We want to divide our network into the following IP address subnets:

One 64 IP address subnet

Four 8 IP address subnets

Four 4 IP address subnets

One 1 IP address subnets (for use with a private IP network)

(rest left for expansion)

Im assuming we configure ports on the 3550 as NO SWITCHPORT ports and define them IP addresses of




im assuming each of our clients on the individual subnets will then use the corresponding IP as its

gateway, but:

-does our provider need to make any changes to the /24 mask they are now giving us?

-how do we set this all up in IOS on the 3550?

-what subnet masks do we give the clients?

-how do we ensure the subnets can talk IP to each if the need to? (routing)

-does any of this involve VLANs?


Re: Need help on a 3550 routing/subnetting

1. If you break it up then your provider will have to change his mask and possibly his address depending on where the connecting link falls in your address scheme.

2. You do not give each port and address . You create a layer 3 SVI on the 3550 "interface vlan XX. You apply the address under the SVI . You then put the ports you want into that vlan that falls within that address range .

3. Your client subnet mask will be whatever the vlan subnet mask is when you break it up(mask determines how many hosts are in each subnet so this needs to be correct) and you will point the client default gateway to the layer 3 SVI address for that subnet .

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