There are many of yesterdays Cisco routers still available that are capable of serving the purpose of a home router. Benefits to this are:

• Get to use the familiar IOS used at work on your home network as well
• These routers are still more powerful than many of the new SOHO routers of today
• Can run modern IOS (12.3) with an easy flash/ram upgrade - allowing you to use many newer features.
• Can be purchased very cheaply - I’ve found them on Ebay for as little as $25.

This article focuses specifically on the Cisco 1605 router, because it has two Ethernet ports. One of the ports will be connected to the cable/dsl modem and the other to an internal switch. The 1605 router uses flash on a PCMCIA card. A 16mb card is all that is needed to hold the image and there is still room for crashdump and configuration file saves. The DRAM can be upgraded by placing a 32Mb chip in the single slot of these routers. I was able to upgrade my 1605 with a SIMM from a 2500 router (same memory).

Here is a show version of the 1605:

(Note: Although 12.3 is available for this device - I am running a 12.2 image to get the feature set needed with the amount of memory I have - only 16mb).

Router#sh ver
Cisco Internetwork Operating System Software
IOS (tm) 1600 Software (C1600-NOSY-M), Version 12.2(46a), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2007 by cisco Systems, Inc.
Compiled Wed 11-Jul-07 19:12 by pwade
Image text-base: 0x02005000, data-base: 0x0293B3CC

ROM: System Bootstrap, Version 11.1(12)XA, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1)
ROM: 1600 Software (C1600-RBOOT-R), Version 11.1(12)XA, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1) 

Router uptime is 1 day, 6 hours, 26 minutes
System returned to ROM by power-on
System restarted at 13:50:23 CST Sat Nov 17 2007
System image file is "flash:c1600-nosy-mz.122-46a.bin"

cisco 1605 (68360) processor (revision C) with 15470K/914K bytes of memory.
Processor board ID 14431821, with hardware revision 00000000
Bridging software.
X.25 software, Version 3.0.0.
2 Ethernet/IEEE 802.3 interface(s)
System/IO memory with parity enabled 16384K bytes of DRAM on SIMM  (On Board Memory disabled)
System running from RAM
7K bytes of non-volatile configuration memory.
16384K bytes of processor board PCMCIA flash (Read/Write)

Configuration register is 0x2102

The following is a working configuration that can be used in a home network environment:

version 12.2
service timestamps debug datetime localtime
service timestamps log datetime localtime
service password-encryption
!
hostname Router
!
aaa new-model
aaa authentication login default local
enable secret <secretpassword>
!
username admin password <adminpw>
clock timezone CST -6
ip subnet-zero
ip domain-name xpresslearn.int
!
ip dhcp pool home_lan
   network 192.168.200.0 255.255.255.0
   default-router 192.168.200.1
   dns-server <isp-dns-ip-1> isp-dns-ip-2>
!
!
!
!
interface Ethernet0
 description Attached to Cable Modem
 ip address dhcp
 ip nat outside
!
interface Ethernet1
 description Internal Network Default Gateway
 ip address 192.168.200.1 255.255.255.0
 ip nat inside
!
ip nat inside source list 100 interface Ethernet0 overload
ip classless
no ip http server
!
access-list 1 remark Allowed telnet management sources
access-list 1 permit 192.168.200.0 0.0.0.255 log
access-list 1 deny   any log
access-list 100 remark Inside Source addresses for NAT Translation
access-list 100 deny   ip any host 192.168.200.1
access-list 100 permit ip 192.168.200.0 0.0.0.255 any
!
line con 0
line vty 0 4
 access-class 1 in
!
ntp clock-period 17042421
ntp server 198.38.16.2
end

This configuration does the following:

•  Enables AAA and sets the default authentication method to using the local defined username/password
• DHCP Server configured for assigning IP addresses to internal clients that are directly connected to the inside interface of the router
• Set’s the outside interface (connected to a cable modem) to DHCP
• Set’s the internal interface (connected to home switch) to 192.168.200.1
• Configures Port Addresses Translation (PAT) to nat the internal addresses behind the dynamically assigned Public IP assigned to the public interface
• Secures the router, so that only trusted IP source networks can telnet to the device
• Configured an ntp server (pool.ntp.org), so that the correct time can be kept up with on the router for logging purposes, etc…