Let's say I have two or three routers and I want the packets sent between them NOT to reach their destination but to "loop" between the routers until TTL runs out." I need to do this in a network simulator called Filius but info about how would this happen in reality or in other network simulator should also help.
If this was your setup:
Host A ---- Router B ---- Router C ---- Router D ---- Host E
Tell Router B that the network for Host E exists at Router C. Tell Router C that the network for Host E exists at Router B.
A packet from Host A to Host E will then get caught in a routing loop between Routers B and C.