Go to this link
http://www.geocities.com/baristhasharma/mimicvlab.html
I have tried it and benefitted a lot.
So wanted to share my experience.
It is just $99 and worths many hundreds dollars.
Has hundreds of Cisco IOS commands. Has lot of
configurations
supported, e.g., RIP, OSPF, EIGRP, Access lists, BGP,
eBGP, NAT, VLAN,
Frame Relay, IS-IS, ISDN, LAN, WAN, Serial links, TFTP
and on and on...
MIMIC Virtual Lab creates a real world lab environment
with a network
of Cisco Routers and Switches. It gives hands-on
learning experience
without buying expensive equipment.
-bs