Eigrp Features; Eigrp Components - Cisco ASR 9000 Series Configuration Manual

Implementing EIGRP
The distance information in EIGRP is represented as a composite of available bandwidth, delay, load utilization,
and link reliability with improved convergence properties and operating efficiency. The fine-tuning of link
characteristics achieves optimal paths.
The convergence technology that EIGRP uses is based on research conducted at SRI International and employs
an algorithm referred to as the Diffusing Update Algorithm (DUAL). This algorithm guarantees loop-free
operation at every instant throughout a route computation and allows all devices involved in a topology change
to synchronize at the same time. Routers that are not affected by topology changes are not involved in
recomputations. The convergence time with DUAL rivals that of any other existing routing protocol.

EIGRP Features

EIGRP offers the following features:
• Fast convergence—The DUAL algorithm allows routing information to converge as quickly as any
• Partial updates—EIGRP sends incremental updates when the state of a destination changes, instead of
• Neighbor discovery mechanism—This is a simple hello mechanism used to learn about neighboring
• Variable-length subnet masks (VLSMs).
• Arbitrary route summarization.
• Scaling—EIGRP scales to large networks.
The following key features are supported in the Cisco IOS XR implementation:
• Provider Edge (PE)-Customer Edge (CE) protocol support with Site of Origin (SoO) and Border Gateway
• PECE protocol support for MPLS.

EIGRP Components

EIGRP has the following four basic components:
• Neighbor discovery or neighbor recovery
• Reliable transport protocol
• DUAL finite state machine
• Protocol-dependent modules
Neighbor discovery or neighbor 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 or neighbor recovery is achieved with low overhead by periodically sending
small hello packets. As long as hello packets are received, the Cisco IOS XR software can determine that a
neighbor is alive and functioning. After this status is determined, the neighboring routers can exchange routing
information.
OL-30423-03
currently available routing protocol.
sending the entire contents of the routing table. This feature minimizes the bandwidth required for EIGRP
packets.
routers. It is protocol independent.
Protocol (BGP) cost community support.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
EIGRP Features
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