Default Eigrp Configuration - Cisco WS-CBS3032-DEL Software Configuration Manual

Configuring EIGRP
EIGRP has these four basic components:
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These sections contain this configuration information:
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Note To enable EIGRP, the switch or stack master must be running the IP services feature set.

Default EIGRP Configuration

Table 39-7
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
39-40
Neighbor discovery and recovery is the process that routers use to dynamically learn of other routers
on their directly attached networks. Routers must also discover when their neighbors become
unreachable or inoperative. Neighbor discovery and recovery is achieved by periodically sending
small hello packets. As long as hello packets are received, the Cisco IOS software learns that a
neighbor is alive and functioning. When this status is determined, the neighboring routers can
exchange routing information.
The reliable transport protocol is responsible for guaranteed, ordered delivery of EIGRP packets to
all neighbors. It supports intermixed transmission of multicast and unicast packets. Some EIGRP
packets must be sent reliably, and others need not be. For efficiency, reliability is provided only
when necessary. For example, on a multi-access network with multicast capabilities (such as
Ethernet), it is not necessary to send hellos reliably to all neighbors individually. Therefore, EIGRP
sends a single multicast hello with an indication in the packet informing the receivers that the packet
need not be acknowledged. Other types of packets (such as updates) require acknowledgment, which
is shown in the packet. The reliable transport has a provision to send multicast packets quickly when
there are unacknowledged packets pending. Doing so helps ensure that convergence time remains
low in the presence of varying speed links.
The DUAL finite state machine embodies the decision process for all route computations. It tracks
all routes advertised by all neighbors. DUAL uses the distance information (known as a metric) to
select efficient, loop-free paths. DUAL selects routes to be inserted into a routing table based on
feasible successors. A successor is a neighboring router used for packet forwarding that has a
least-cost path to a destination that is guaranteed not to be part of a routing loop. When there are no
feasible successors, but there are neighbors advertising the destination, a recomputation occurs. This
is the process whereby a new successor is determined. The amount of time it takes to recompute the
route affects the convergence time. Recomputation is processor-intensive; it is advantageous to
avoid recomputation if it is not necessary. When a topology change occurs, DUAL tests for feasible
successors. If there are feasible successors, it uses any it finds to avoid unnecessary recomputation.
The protocol-dependent modules are responsible for network layer protocol-specific tasks. An
example is the IP EIGRP module, which is responsible for sending and receiving EIGRP packets
that are encapsulated in IP. It is also responsible for parsing EIGRP packets and informing DUAL
of the new information received. EIGRP uses DUAL for routing decisions, but the results are stored
in the IP routing table. EIGRP is also responsible for redistributing routes learned by other IP
routing protocols.
Default EIGRP Configuration, page 39-40
Configuring Basic EIGRP Parameters, page 39-43
Configuring EIGRP Interfaces, page 39-44
Configuring EIGRP Route Authentication, page 39-45
EIGRP Stub Routing, page 39-46
Monitoring and Maintaining EIGRP, page 39-46
shows the default EIGRP configuration.
Chapter 39 Configuring IP Unicast Routing
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