The problem of Cisco router size - BGP routing table

Question: I'm looking for some guidance in sizing Cisco routers for different levels of BGP support.  I'm aware that it requires 1 GB of RAM to handle the full BGP routing table, but the processing required to maintain neighbors/sessions, etc., would be too much for a Cisco 1941 ISR, for example.  I'd like recommended solutions for the following scenarios:

1) A router that will be dual-homed to two different ISP's (same speed lnks - let's say 100-Mb each), and will be maintaining a full routing table to choose the best path based on BGP path attributes.  So, in this case, the router will not be offering Internet transit services.

2) Same router, but it will only be storing a select number of Internet routes (for key sites/businesses - let's say 1,000 routes.)  Still, no transit traffic.

3) Lastly, an ISP router maintaining full Internet routing table (322K routes as of today), and three OC3 connections to other ISP neighbors.

The solution:

Hardset requirements:

BGP Full table, Cisco recommends 1GB of RAM

CEF Requirements (if enabled [enabled on most by default])256-512MB of RAM

RIB Requirements (256-512MB)

iBGP = Branch routers

eBGP = WAN/Edge Routers

http://www.cisco.com/en/US/products/hw/routers/ps359/products_tech_note09186a0080110d68.shtml#ts1

http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a00800949e8.shtml

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a83.shtml

Branch routers have rinky dink processors, very low throughput and not intended for any type of service as an edge device for production traffic. Running eBGP, a full table, I would not even consider looking at any ISR routers. I focus on anything that is for enterprise and service provider edge applications, in your case: Internet Edge Routers

armed with new information

- eBGP w/ two ISP's (no iBGP)

- let's say partial BGP routes this time (let's go with approximately 1,000)

- OSPF locally, but minimal OSPF routes (let's say less than 20)

- no other services or processes

You also have to take cost into consideration:

This does not justify the need for a 7200 or a ASR as your requirement does not include a full table, however, with multiple peers, eBGP, a beefier processor would be needed. The only router that supports anything above 200Mbps (100Mbps plus 100Mbps downstream to your network ) is the 3900 series based on packets per second. Note: The ISR routers feature an ASIC bus, replacing the PCI bus found in older routers. Please note that unlike ASIC driven switches and routers, the ASIC found in the ISR line of routers is just for bus operation only. Routing functions are still fully handled by the CPU

http://www.cisco.com/web/partners/downloads/765/tools/quickreference/routerperformance.pdf

The 2800 routes do not have the performance to meet 200Mbps.

Customers interested in purchasing Cisco router or its price, please refer to below links:

Cisco 2951 price

Cisco 2901 price