What is a common consequence of MED misconfiguration?

• A. Misconfiguration of MED can reveal topology or affect traffic flows.
• B. MED misconfiguration has no impact.
• C. MED is only relevant for IPv6.
• D. MED automatically hides topology.

Answer: (A)

MED, or Multi-Exit Discriminator, is a BGP path attribute that acts as a hint to neighboring ASes about which exit points from your network you prefer for inbound traffic. Because it’s a hint rather than a hard rule, how routers honor it can vary, but when peers do consider MED values, they may adjust routing to favor certain paths.

If MED is misconfigured, two common consequences show up. First, it can affect traffic flows: neighboring networks may redirect inbound traffic along unintended exit points, leading to suboptimal paths, potential congestion on some links, or unexpected changes in latency and throughput. Second, it can reveal topology: the MED values convey information about the relative positions of your exits and how your network is connected to different upstreams, so external parties can infer internal routing choices or the existence of multiple links.

So the misconfiguration doesn’t just sit quietly; it can both change how traffic enters your network and reveal how your network is laid out to outsiders.