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Enhanced Interior Gateway Routing Protocol
Valid values for the administrative distance range from 1 to 255. Again, the
lower the value, the better. If an administrative distance of 255 is chosen,
routes will be considered unreachable and will be ignored.
When redistributing static routes or other protocol types within EIGRP,
metrics may be set for these routes as well by using the default-metric
default-metric bandwidth delay reliability load mtu
Bandwidth and delay have a range of values from 0 to 4,294,967,295 (in
Kbps) and 0 to 4,294,967,295 (in 10-microsecond units), respectively. Reli-
ranges from 0 to 255, with 255 being the most reliable. Load ranges
from 0 to 255; however, a value of 255 means that the link is completely
loaded. Finally, the value of MTU has the same range as the bandwidth vari-
able: 0 to 4,294,967,295.
Most of this information should be a review, since it's basically the same
information associated with IGRP.
Load Balancing
One of EIGRP's major enhancements is its ability to select more than one
primary route or successor. We have discussed how route costs are calcu-
lated and shown that up to six routes for every destination can be stored in
the topology database. EIGRP capitalizes on this information.
By using multiple LAN or WAN connections from one router to another,
multiple routes can exist to the next-hop address. When the links are sym-
metric (meaning they have the same circuit type and the same bandwidth
capacity), the same local cost is assigned to each link.
Since both links have the same feasible distance, the metrics for destina-
tions accessible via the links will be equal. As EIGRP chooses the successor
for a route, it looks for the route with the lowest cost. When it sees multiple
routes with the same metric, it selects them all as successors. EIGRP will then
share traffic loads across each of the multiple links. This is called load
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