Configuring IGRP on a 2501 (according to Todd Lammle's book)

I have been studying for my ccna sice start of Feb this year - I have
a lab consisting of 1 x 2501 router and 2 x 2503 router and 2 1900
catalyst switches...I am using Todd Lammle's Sybex book as my text.

Currently on Chapter 5, and having configured RIP on the router, the
text advises to configure IGRP over this existing configuration - when
I list the available protocol's the list returned contains:

bgp
eigrp
iso-igrp
ospf
rip

and one or two others

Could anyone advise why this Cisco 2501 router doesnt have the basic
(and cisco proprietary) protocol IGRP

and if possible, advise if and how I go about finding and loading this
type of protocol if it is at all possible?

My 3rd question is....

The text speaks about configuring the practice labs with more than the
3 basic routers which I have - for instance the one I am currently
looking at uses 3 x 2501 routers and 1 x 2621 router which I am not
able to configure because I dont have one. I was able to do the lab on
paper only due to this.

Anyone know the best way of connecting my 3 real life routers with say
a virtual termulation of a 2621 type router (as an example) as im sure
further into the book the config's the netwotrks become much much
bigger....

Or am I best biting the bullet and getting the Bosom simulator for
such instances?