10-22
Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
78-15224-02
Chapter 10 Configuring Networking Protocols
Configuring IP Routing
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 must occur.
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 asks DUAL to make 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.
Table 10-4 shows the default EIGRP configuration.
Table 10-4 Default EIGRP Configuration
Feature Default Setting
Auto summary Enabled. Subprefixes are summarized to the classful network
boundary when crossing classful network boundaries.
Default-information Exterior routes are accepted and default information is passed
between IGRP or EIGRP processes when doing redistribution.
Default metric Only connected routes and interface static routes can be redistributed
without a default metric. The metric includes:
• Bandwidth: 0 or greater kbps.
• Delay (tens of microseconds): 0 or any positive number that is a
multiple of 39.1 nanoseconds.
• Reliability: Any number between 0 and 255 (255 means
100 percent reliability).
• Loading: Effective bandwidth as a number between 0 and 255
(255 is 100 percent loading).
• MTU: Maximum transmission unit size of the route in bytes. 0 or
any positive integer.
Distance Internal distance: 90.
External distance: 170.
EIGRP log-neighbor changes Disabled. No adjacency changes logged.
IP authentication key-chain No authentication provided.
IP authentication mode No authentication provided.
IP bandwidth-percent 50 percent.
To Next Page
Loading...
