over which traffic is balanced. The need for this function is straightforward; some other
considerations about when to use it are subtle. Figure 8-27 illustrates the most obvious need for
Multilink PPP.
Figure 8-27 shows two dotted lines between the PC and the access server, signifying that two
B channels are in use between the devices. Multilink PPP breaks a packet into fragments, sends
some fragments across each of the two links, and reassembles them at the other end of the link.
The net result is that the links are utilized approximately the same amount.
between Atlanta and Nashville uses six B channels between two routers.
negative is that the routers must fragment and reassemble every packet. However, the 384Kb
needed for the video conference is available.
links. Six routes to subnet 10.2.2.0/24 would exist in Router A's routing table. With any of the
faster internal switching methods in a Cisco router (fast switching, optimum switching,
NetFlow switching), the balancing effect is that all packets to the same IP address use the same
link. The result is that router Atlanta sends some packets over one link and some over the other,
but the balancing is unpredictable. More importantly, all packets to the videoconference
system's single IP address in Nashville will use the same link, effectively limiting the
videoconference to 64 kbps. An alternative is to disable the faster switching methods in the
router so that multiple routes to the same subnet are used in a round-robin fashion. However,