end result is that the central site knows all routes, but the remote sites are unable to reach each
other because the central site is not allowed to send updates to them. Figure 9-5 illustrates the
concept of split horizon.
broadcast traffic. NBMA networks do not enable the propagation of broadcasts through the
network. Therefore, the broadcast must be transmitted over each individual VC. In other words,
the broadcast goes into a broadcast queue and is sent one time for each circuit being serviced
(10 VCs = 10 broadcasts). These broadcasts can consume large amounts of bandwidth in a short
time, depending on the volume of broadcast traffic being sent.
Based on traffic patterns and utilization of links, you can add additional connections between
remote sites and increase the bandwidth available to each site. This can assist in dealing with
broadcast traffic as well as other high-volume traffic types.
however, the correct action to take because turning off split horizon can be difficult. In fact, IP
is usually the only protocol that allows it to be disabled. By default, IPX and AppleTalk don't
allow split horizon to be disabled; however, with EIGRP as the routing protocol for IPX and
AppleTalk, it is possible (but problematic) to disable split horizon. Unfortunately, once split
horizon is disabled, routing loops can easily occur and cause routes to be erroneously
advertised.
subinterface is a logical division of a physical interface (hereafter known as a major interface).