System information

82 Chapter 3: Defending the Perimeter
the router architecture. Although Cisco offers a wide range of router platforms, ISR models
are easy to identify, because the last three digits of their model begin with the number 8. As
shown in Figure 3-1, the ISR family of routers includes the 800 series, 1800 series, 2800
series, and 3800 series.
Figure 3-1 800 Series, 1800 Series, 2800 Series, and 3800 Series ISRs
Cisco 800 Series
The Cisco 800 series of ISRs is designed for teleworkers and small-office environments.
These routers can connect to the Internet via a cable modem or DSL modem connection and
offer secure connections over the Internet. Table 3-3 contrasts some of the features available
in the Cisco 850 and 870 series of ISRs.
Table 3-3 Cisco 800 Series of ISRs
Feature Cisco 850 Series Cisco 870 Series
WAN technology
support
ADSL Annex A (Cisco 857) ADSL Annex B (Cisco 876),
ADSL Annex A (Cisco 877),
G.SHDSL (Cisco 878)
Built-in routed/WAN
Ethernet
One 10/100 WAN (Cisco
851)
One 10/100 WAN (Cisco
871)
Integrated
cryptographic
hardware
Yes Yes
Maximum flash
memory
20 MB 52 MB
Maximum SRAM
64 MB 256 MB
Support for Cisco
Security Device
Manager (SDM)
Yes Yes
Cisco 3800 Series Router
Cisco 800 Series Router Cisco 1800 Series Routers
Cisco 2800 Series Router