Tag Archives: 3.5

3.5 eigrp bw and dly table

dly and bw eigrp

http://blogs.interfacett.com/ciscos-eigrp-metric-fact-and-not-so-fact

the above is an excellent explanation of this tricky subject.

reduction:

METRIC=256∗[( k1∗bandwidth) + (k3∗delay)]

or better yet

METRIC=256∗(BW+Delay)

FastEthernet0/0 is up, line protocol is up
Hardware is AmdFE, address is cc01.0bb4.0000 (bia cc01.0bb4.0000)
Internet address is 192.168.16.1/24
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

R1#sh int lo0
Loopback0 is up, line protocol is up
Hardware is Loopback
Internet address is 10.10.10.10/24
MTU 1514 bytes, BW 8000000 Kbit, DLY 5000 usec,

R1#sh int s3/0
Serial3/0 is up, line protocol is up
Hardware is M4T
Internet address is 172.20.15.2/30
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

and this excellent article from:

https://learningnetwork.cisco.com/docs/DOC-13825

EIGRP_Metric_Calculation_Demystified

http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/16406-eigrp-toc.pdf

metric = 10^7 (10000000) divided by least bandwidth along the given path + cumulative delay along the path times 256

3.5 EIGRP [for IPv4 and IPv6]

EIGRP offers the following features:

● Fast convergence—The DUAL algorithm allows routing information to converge as quickly as any currently available routing protocol.

● Partial updates—EIGRP sends incremental updates when the state of a destination changes, instead of sending the entire contents of the routing table. This feature minimizes the bandwidth required for EIGRP packets.

● Less CPU usage than IGRP—This occurs because full update packets need not be processed each time they are received.

● Neighbor discovery mechanism—This is a simple hello mechanism used to learn about neighboring routers. It is protocol-independent. Security requirements do not allow dynamic learning of neighbors. BFD should be used to detect loss of a neighbor.

● Variable-length subnet masks (VLSMs).

● Arbitrary route summarization.

● Scaling—EIGRP scales to large networks.

EIGRP uses split horizon or advertises a route as unreachable when:

● two routers are in startup mode (exchanging topology tables for the first time)

● advertising a topology table change

● sending a query

Poison reverse is a loop avoidance mechanism that states that once you learn of a route through an interface, advertise it as unreachable back through that same interface.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 3007-3011).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfeigrp.html