A system (100, 290, 700) comprising: a cache module, stored in memory, configured to store a neighbor cache entry that specifies whether a neighbor of a network node is reachable according to a detection mechanism of a neighbor unreachability detection protocol; a timeout module, stored in memory, configured to specify a timing interval in which to select a reachable time threshold that defines a length of time during which the neighbor is designated as reachable according to the neighbor unreachability detection protocol; a reception module, stored in memory, configured to receive event information about whether the neighbor is active, wherein the event information about whether the neighbor is active comprises at least one of: a network bridge record of a media access control address that corresponds to both the neighbor and a packet that arrived at a corresponding network bridge; and information about a network packet sampled at an interface of the network node attempting to determine whether the neighbor is reachable; a biasing module, stored in memory, configured to bias, based on the received event information about whether the neighbor is active, a selection of the reachable time threshold within the timing interval by performing at least one of: altering a size of the timing interval; and focusing the selection of the reachable time threshold on a subset of the timing interval; a determination module, stored in memory, configured to determine whether the neighbor is reachable based at least in part on a determination of whether the selected reachable time threshold has been satisfied; and at least one physical processor configured to execute the cache module, the timeout module, the reception module, the biasing module, and the determination module. a cache module, stored in memory, configured to store a neighbor cache entry that specifies whether a neighbor of a network node is reachable according to a detection mechanism of a neighbor unreachability detection protocol; a timeout module, stored in memory, configured to specify a timing interval in which to select a reachable time threshold that defines a length of time during which the neighbor is designated as reachable according to the neighbor unreachability detection protocol; a reception module, stored in memory, configured to receive event information about whether the neighbor is active, wherein the event information about whether the neighbor is active comprises at least one of: a network bridge record of a media access control address that corresponds to both the neighbor and a packet that arrived at a corresponding network bridge; and information about a network packet sampled at an interface of the network node attempting to determine whether the neighbor is reachable; a network bridge record of a media access control address that corresponds to both the neighbor and a packet that arrived at a corresponding network bridge; and information about a network packet sampled at an interface of the network node attempting to determine whether the neighbor is reachable; a biasing module, stored in memory, configured to bias, based on the received event information about whether the neighbor is active, a selection of the reachable time threshold within the timing interval by performing at least one of: altering a size of the timing interval; and focusing the selection of the reachable time threshold on a subset of the timing interval; altering a size of the timing interval; and focusing the selection of the reachable time threshold on a subset of the timing interval; a determination module, stored in memory, configured to determine whether the neighbor is reachable based at least in part on a determination of whether the selected reachable time threshold has been satisfied; and at least one physical processor configured to execute the cache module, the timeout module, the reception module, the biasing module, and the determination module.