I've got a scenario where we purchased two Cisco 2851 routers and from reading the information below, it says that we will get sub-rate speeds and the Cisco 2800 series routers are not recommended for DS3. We've already bought the routers and so we need to use them.
My question is that what will I get the same performance as if it had the Cisco 3845 or at least close to the same performance on the Cisco 2851 routers.
Q. Does the Cisco 2800 Series support a T3/E3 interface?
A. The Cisco NM-1T3E3 is supported on the Cisco 2811, 2821 and 2851 platforms. This module provides customers with a connectivity option for a DS3 interface, but only at sub-line rates. As shown Table 1, the Cisco 2800 Series routers are designed to be T1/E1 routers, not DS3 routers. Although some customers may achieve line rate or near line rate on a DS3 with no services, the addition of common services such as access control lists (ACLs), quality of service (QoS), and IP Security (IPSec) will each cause performance degradation. The recommended platform for T3/E3 connectivity is the Cisco 3800 Series.