From: David M Anderson (dma@xxxxxxxxx)
Date: Thu Jan 18 2001 - 14:39:58 GMT-3
Here is some info on IGRP and EIGRP metrics that might be of assitance to someo
ne:
1.1.2.1 - IGRP bandwidth
IGRP bandwidth (bits) = (10*1010 / BW (bps)) div 1
Min BW = 1200 bps: Max IGRP bandwidth = (10*1010 / 1200) div 1 = 8 333 333
Max BW = 10 Gbps: Min IGRP bandwidth = 10 / 10 = 1
Loopback BW = 10 000 000 000 bps; IGRP bandwidth = 1
Satelite BW = 500 000 000 bps; IGRP bandwidth = 20
Ethernet BW = 10 000 000 bps; IGRP bandwidth = 1000
Serial BW = 2 000 000 bps; IGRP bandwidth = 5000
Serial BW = 512 000 bps; IGRP bandwidth = 19531
Serial BW = 64 000 bps; IGRP bandwidth = 156250
Serial BW = 9 600 bps; IGRP bandwidth = 1041666
1.1.2.2 - EIGRP bandwidth
EIGRP bandwidth (bits) = 256*((1010 / BW (bps))div 1)
Min BW = 1200 bps: Max EIGRP bandwidth = 256*((1010 / 1200) div 1) = 2 133 333
248
= 256*(8333333.33 div 1)
= 256*8333333
Max BW = 25.6 Gbps: Min EIGRP bandwidth = 25.6 / 25.6 = 1
Loopback BW = 10 000 000 000 bps; EIGRP bandwidth = 256
Satelite BW = 500 000 000 bps; EIGRP bandwidth = 5 120
Ethernet BW = 10 000 000 bps; EIGRP bandwidth = 256 000
Serial BW = 2 000 000 bps EIGRP bandwidth = 1 280 000
Serial BW = 512 000 bps; EIGRP bandwidth = 4 999 936
Serial BW = 64 000 bps; EIGRP bandwidth = 40 000 000
Serial BW = 9 600 bps; EIGRP bandwidth = 266 666 496
1.2 - Composite metric
A weighted value for the different metrics that are taken into account. Differe
nt routing protocols use different metrics for calculating the composite
metric.
For RIP, hop count is the only metric and as such, in RIP the hop count is the
composite metric.
palm#show ip route 150.150.1.0 255.255.255.0
Routing entry for 150.150.1.0 255.255.255.0
Known via rip, distance 120, metric 2
Redistributing via rip
Advertised by rip (self originated)
Last update from 150.150.45.4 on Serial1, 00:00:04 ago
Routing Descriptor Blocks:
* 150.150.45.4, from 150.150.45.4, 00:00:04 ago, via Serial1
Route metric is 2, traffic share count is 1
For IGRP and EIGRP, by default we use bandwidth and delay, but load and reliabi
lity can also be taken into account.
The weight that we assign to each metric can be tuned using the metric weights
router subcommand:
metric weights tos k1 k2 k3 k4 k5
With default metric weights k1=1, k2=0, k3=1, k4=0, k5=0, ie no metric weights:
Metric = bandwidth + delay
Note that the bandwidth will be the lowest bandwidth en route, thus the highest
bandwidth value.
The full definition:
Metric = (k1*bandwidth + k2*bandwidth/(256 - load) + k3*delay) *
(k5/(reliability + k4)
IGRP's composite metric is 24 bits, where EIGRP uses 32 bits.
David Anderson
Lab Engineer
(408) 853-5515
dma@cisco.com
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