Free 200-301 flashcards

When several routes in the table all match a destination, what is the first test the router applies to choose one for forwarding?

Longest prefix match is applied first: the router picks the route whose mask covers the destination with the most bits set. Administrative distance and metric act as tie-breakers only when two routes share the identical prefix, so a /24 beats a /16, /8, or default outright.

OSPF's lower administrative distance than EIGRP means its /16 route is chosen over an EIGRP /24 for the same destination.

Administrative distance only breaks ties between routes to the SAME prefix. With different prefix lengths the longest match is chosen first, so the /16 is never compared by AD against the more specific /24.

When an IPv6 host self-configures a link-local address with no router present, which prefix does it use and why does that traffic stay on one link?

Every IPv6 interface generates a link-local address from fe80::/10 for on-link functions such as neighbour discovery. Routers are required never to forward packets whose source or destination is link-local, so the address scope is confined to exactly one link.

Is fc00::/7 the prefix a host self-assigns for link-local communication when no router is present?

No. fc00::/7 is the unique local address (ULA) range, which is site-scoped and can be routed between internal subnets. It is not the prefix a host self-assigns for link-local communication, so it is the wrong classification.

Two switches share an 802.1Q trunk but disagree on the native VLAN (1 versus 99). What happens, and why does the link stay up?

Each switch sends its own native-VLAN traffic untagged, and the neighbour places any untagged frame it receives into ITS own native VLAN. So VLAN 1 frames from one side are absorbed into VLAN 99 on the other, bridging the two VLANs together. The physical link never goes down, which is what makes the leak subtle.

A native VLAN only affects which VLAN carries management traffic, so a native-VLAN mismatch never touches the forwarding of user data.

It is tempting because a native-VLAN mismatch does not bring the physical link down. But the mismatch does affect user data: untagged frames leak between the two different native VLANs, bridging them together.

In security terms, what is an unpatched coding flaw in software classified as, and how does that differ from a threat or an exploit?

It is a vulnerability: a weakness in the system that could be leveraged to compromise it. The threat is the potential danger or actor that could act against it, and the exploit is the specific code or technique that takes advantage of the weakness. The coding flaw is the weakness being targeted, so it matches the definition of a vulnerability.

Is the coding flaw a threat, because it represents the party with intent and capability to harm the server?

No. A threat is the potential danger or the actor that could cause harm, such as the attacker. The coding flaw is the internal weakness being targeted, not the source of danger, so the term is misapplied.