Cisco router to handle traffic for multiple subnets

Hi Cisco Router Experts:

I have a question regarding the best way to grow my network.  I provide Internet to a couple hundered customers and use private static IPs (10.50.10.x -  I use a cisco 2621 router as gateway  

I've outgrown the single subnet and want to add new customers on 10.50.20.x addresses.

What is the best recommendation for this expansion?  Should I just add another cisco router as  Or can the single cisco router act as a gateway for multiple subnets?  If so, what commands would I need to add.

Thanks for your advice!

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rfc1180Connect With a Mentor Commented:
You could essentially do what you asking with no issues; I am sure cost is a factor is you can pick a 2621 for barely nothing. As I said, you could just use one 2621 (if you have enough resources) and depending on the switches you have on the network (You essentially could use 802.1q and trunking, if your switches support the technology).  Note, that the 2621 can only handle about 12Mbps of traffic; so for a couple hundred customers, one 2621 might not handle any future growth. Yes, what you have on your simple diagram you can do with no issues.

rfc1180Connect With a Mentor Commented:
The Cisco 2621 (non XM) handles about 25Kpps @ 64Byte packets, so depending on what you are utilizing now, you might need to add an additional router. Due to the fact that the 2621 is end of life and support, you would be better off just upgrading the existing router to a router that will support your existing customers, and any new customers in the future (Scalability). I would create a new network ID from a subnet perspective because extending the subnet mask to a /23 will require an update to all your customers subnet mask. Depending on how your infrastructure is laid out (distribution layer and access layer) you might need a redesign. Do you have a current network diagram?

kf4zmtConnect With a Mentor Commented:
The router can handle multiple subnets if it has the proper IOS to do trunking.  This would mean that your new subnets that you are going to add are in a different vlan on the switch.  The connection from the switch to the router would need to be a trunk and the router would need to be configured with Ethernet sub-interfaces each running dot1q encapsulation.
dkbeckstromAuthor Commented:
@rfc1180  I don't have a formal network diagram, but it's pretty simple.

                                                         |-> Cisco 2621(10.1) -|
(DSL1, 2, 3,) -> Peplink Aggregator |                                  |  -> Cisco Switch -> Customers
                                                         |-> Cisco 2621(20.1) -|

This is the basic design I have in mind (if my ascii text translates properly).  I'm just wondering if the additional router is necessary or recommended.

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