Is there any occasion we do not need redistribution looping prevention?

[George-Sl]

I saw in some examples in a book

where there is a two way redistribution, and there is no method defined to tag or any other way to prevent re-redistribution of already redistributed route

is routing info loop can be happened between any two protocol(even because one has a worst external AD)? for example even between rip and ospf?

or in other word is there any circumstance where there is a two way redistribution and routeing info loop not happen?

thanks

[Reza Sharifi]

Hi George,

Usually if there is a single point of redistribution routing loop does not happen, because once you redistribute a route from one protocol to another, the AD for that route will change to reflect the redistribution.   For example; if you are receiving a route from a provider via eBGP, the route has an AD of 20 (This is in Cisco world). Now once you redistribute that route to say OSPF the AD for the route will change to 110.  If you have multiple points of distribution with multiple protocols, you could end up with some sort of routing loops and in that case you would need to adjust ADs.

HTH