A packet is allowed only if the best (longest‑match / preferred) route back to the source IP would exit the same interface the packet arrived on. [rfc-editor.org],
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A packet is allowed only if the best (longest‑match / preferred) route back to the source IP would exit the same interface the packet arrived on.
Think: “Would I send the reply back out the same interface?”
If no → drop.
✅ Loose RPF (uRPF loose)
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A packet is allowed if the firewall/router has any route at all to the source IP (regardless of interface). It’s basically a route existence check. [rfc-editor.org]
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A packet is allowed if the firewall/router has any route at all to the source IP (regardless of interface). It’s basically a route existence check.
