This page was exported from Free Cisco Training & Resources - Certification Exam Preparation [ https://www.ciscobibles.com ] Export date:Wed Mar 12 15:29:56 2025 / +0000 GMT ___________________________________________________ Title: CCNP BSCI Notes - EIGRP Principles --------------------------------------------------- Supports routed protocols like IP and IPv6 via protocol-dependent modules Uses Reliable Transport Protocol (RTP, Cisco proprietary) for some traffic (updates, queries, and replies) Uses hellos to identify/monitor neighbors Uses the Diffusing Update Algorithm (DUAL) to select routes EIGRP is IP protocol 88. EIGRP supports proportional unequal-cost load-balancing among feasible routes. Packet types          Hello - Identify neighbors, sent as periodic multicasts          Update - Advertises routes, only sent when there is a change, multicast to 224.0.0.10          Ack - Acknowledges receipt of an update          Query - Used to query routes from neighbors (multicast; unicast attempted up to 16 times if multicast gets no response)          Reply - Used to answer a query (unicast) Metric calculation Metric = 256 * (K1 * bandwidth + ( (K2 * bandwidth) / (256 - load) ) + K3 * delay) * ( K5 / (reliability + K4)) K values are used to distribute weight to different path aspects:            bandwidth - Defined as 107 divided by the speed of the slowest link in the path, in Kbps            load - 8-bit value, not considered by default            reliability - 8-bit value, not considered by default            delay - constant value associated with interface type; EIGRP uses the sum of all delays in the path K defaults: K1 = 1, K2 = 0, K3 = 1, K4 = 0, K5 = 0 K values can be manipulated by an admin, but routers must have matching K values to become neighbors DUAL         Advertised distance - Cost advertised by a neighbor to get to a destination         Feasible distance - Advertised distance + cost get to that neighbor The feasibility requirement states "if my neighbor's advertised distance is less than my feasible distance, the path will be loop free."         Successor - The neighbor with the best path         Feasible successor - All other neighbors which meet the feasibility requirement         Split-horizon - A network is not advertised on the link from which is learned. Queries When a router loses its successor and has no feasible successors, it will query all remaining neighbors for a new route. Queries are recursive and will be forwarded to other neighbors until either a route is found, or a summarization boundary is reached. Stuck in Active (SIA) - Queries which do not return a route before the active timer expires (usually 3 minutes), the router is considered stuck in active mode. EIGRP Tables Neighbor table Stores information about neighboring EIGRP routers:          Network address (IP)          Connected interface          Holdtime - how long the router will wait to receive another HELLO before dropping the neighbor; default = 3 * hello timer          Uptime - how long the neighborship has been established          Sequence numbers          Retransmission Timeout (RTO) - how long the router will wait for an ack before retransmitting the packet; calculated by SRTT          Smooth Round Trip Time (SRTT) - time it takes for an ack to be received once a packet has been transmitted          Queue count - number of packets waiting in queue; a high count indicates line congestion Topology table Holds all routes received from neighbors, is built from updates, calculated by DUAL, and contains all the information required by the routing table Routing table Route types:           Internal - Paths directly within EIGRP           Summary - Internal paths which have been summarized           External - Routes redistributes into EIGRP --------------------------------------------------- Images: --------------------------------------------------- --------------------------------------------------- Post date: 2009-11-12 15:23:24 Post date GMT: 2009-11-12 07:23:24 Post modified date: 2010-07-24 14:24:55 Post modified date GMT: 2010-07-24 06:24:55 ____________________________________________________________________________________________ Export of Post and Page as text file has been powered by [ Universal Post Manager ] plugin from www.gconverters.com