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Voyager Reference Guide
implementations allow such packets. It is possible to disable some of
these checks for request packets, but not for the update packets.
Valid Neighbors: In this implementation, packets that have a source
address from a non-local network are ignored. It is not possible to disable
this behavior.
Duplicate Entries in an Update: In this implementation, if there are
duplicate new paths in an update message, holddowns are enabled, and
each of the duplicate composite metrics differ by more than 10 percent,
the route is not put in holddown. The path with the best metric is installed.
Other implementations treat each duplicate path as if it arrived in separate
update messages. In this case, the route should be placed into holddown.
Triggered Update on Route Expiration: In this implementation, when a
route expires, a triggered update message is generated at the moment of
expiration, marking the route as unreachable. Other implementations wait
until the next scheduled update message to mark the route as unreachable.
In this latter case, the route is actually not marked as unreachable until the
next scheduled update cycle (though this seems somewhat contradictory).
Specific Split Horizon: This implementation does not implement
specific split horizon. Split horizon processing roughly means that routes
learned from an interface are not advertised back out that same interface.
Specific split horizon occurs when a request is made. In this case, only
routes that use the requestor as the next hop are omitted from the
response.
Poison Reverse: This implementation uses simple split horizon; that is,
poison reverse is not performed. Other implementations use a form of
poison reverse in which at least a single update advertises an expired
route as being unreachable on the interface from which the route was
learned.
Forwarding to Unreachable Routes: In this implementation, when a
route expires or is marked as unreachable from the originator, the route is
removed from the forwarding table. In the absence of a default or more
general route, packets destined for this address are dropped. Other
implementations continue to forward packets to routes marked as
unreachable until a route is flushed from the table.
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