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Just one question. I have reth interfaces reth0 to reth3 and I want to assign each reth interface to each RG. So the RG wil be from RG1 to RG4 means reth0 assigned to RG1, reth1 to RG2 and so no.
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Multiple RGs are used for active-active configuration. If you do things this way, you will force traffic to traverse the data connection (fabric link) between the two members, a lot. I really don't see any benefit.
In most configurations, keeping all interfaces in RG1, so they fail over together, is the way to go.