SSH for Cisco IOS
SSH in IOS. Recent Cisco-router firmware (IOS 12.x on some models only — Cisco 2500 and 1700 series not being supported for performance reasons) is said to include a Cisco-written implementation of ssh 1.5, server and client. Note that international versions of IOS are limited to DES session encryption, only.
Jim Dennis notes: One way to gain secured access to older Cisco routers, or smaller (2500 or 1700) or other devices with serial consoles is to run a null modem cable to them from any nearby Unix, Linux, FreeBSD box — ssh thereto and use cu, tip, minicom, or kermit.