Sub optimal routing & routing loops

Experts

Can you help more with my understanding of

1. Sub optimal routing does this occur mainly in ospf when a router is running two processes preferring IA over E1 E2 / what other protocols would you include I understand eigrp would not be affected as external routes have ad of 170 therefore it would not be chosen for a certain prefix if eigrp internal was known as ad is better? Need some examples isis/ bgp/rip

2. Routing loops mainly occur when redistribution is taking place and the best way to tackle is use of route maps, can you provide some examples

Sorry might seen like a basic question.

TIA

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BR
Tony
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