Scenario: A Citrix Administrator manages a Citrix SDX appliance with several instances configured. The administrator needs to enable Layer 2 mode on two instances. When using a shared network…

Imani T.May 18, 2026

C is your answer. On an SDX with a shared interface, multiple instances need a way to distinguish whose traffic is whose, and MAC-based forwarding mode handles that by routing traffic based on MAC addresses instead of relying on IP, which keeps things clean when two instances are both operating in Layer 2 mode on the same physical link.

Luis F.May 12, 2026

So I actually got tripped up on this one at first because I thought enabling tagging on the interfaces (option B) would be enough to separate the traffic, but tagging is more about VLAN separation and not really about how the SDX figures out which instance owns which frames on a shared NIC. The key here is that when two instances are running Layer 2 mode on the same shared interface, the SDX has no reliable IP-level way to differentiate who owns incoming frames, so it needs to fall back on MAC addresses instead. MAC-based forwarding mode tells the SDX to forward traffic to instances based on the destination MAC address, which is exactly what you need when L2 mode bypasses the normal routing logic. That is why option C is the right call, the MBF mode fills the gap that L2 mode creates when sharing physical interfaces between instances. Genuine question though, does MBF only kick in for traffic that would otherwise be ambiguous, or does enabling it change how ALL traffic is forwarded on that instance even for packets that have a clear destination IP? I have been trying to wrap my head around whether it is a fallback mechanism or a full mode swap.

Lena V.May 25, 2026

Took me a second on this one because I almost went with B, but remember that tagging is about VLAN separation, not about solving the forwarding ambiguity you get when two instances share a physical interface in L2 mode. MBF (C) is what tells the SDX to forward return traffic based on the destination MAC rather than doing a route lookup, which is exactly what breaks without it when you have multiple instances on the same interface.

Bao N.Jun 2, 2026

Tagging on shared interfaces is what keeps traffic lanes separated, pick B.