[comp.dcom.sys.cisco] Warning about RIP <-> IGRP redistribution

kwe@bbn.com (Kent W. England) (05/16/91)

In article <5955@ns-mx.uiowa.edu> jnford@argos.weeg.uiowa.edu (Jay Ford) 
writes:
> Does this mean that I can run IGRP and RIP simultaneously on my class B 
net,
> and redistribute routes between the two protocols? 

As a matter of fact, you can run multiple instances of IGRP and one RIP 
process all at the same time.   But don't forget that extra routing 
processes are expensive in update bandwidth and memory.  Use passive 
interfaces where possible.  But multiple IGRP processes can get you some 
of the route tagging capability of OSPF and save building some filter 
lists.

You must be careful in redistributing routing processes symmetrically.  
This is almost guaranteed to create routing loops, as there are no 
"split-horizon" rules for cisco redistribution between processes.
For example, if you redistribute RIP into IGRP  and then redistribute IGRP 
back into RIP, your router will loop RIP routes back out to the source 
network .  Two router routing loops will result.  You must use filter 
lists to prevent this occurring.

--Kent