CMS 512MB (1X512MB) DDR1 2100 266MHZ ECC Registered DIMM Memory Ram Upgrade Compatible with Cisco® 2811 Router Main Memory DMemory Ram Upgrade2811-512D for Server Only - C89 at Amazon.com
CISCO1921/K9-C3 Cisco 1900 Series IEEE 802.1ag 512MB RAM 256MB Flash M
Cisco MEM1841-64D 64MB DRAM Memory Module for Cisco Router 1841