Metric EIGRP – 5 criteria:
– K1 – Bandwidth.
– K2 – Load.
– K3 – Delay.
– K4 – Reliability.
– K5 – MTU.
Or EIGRP gets this information:
By default, EIGRP uses only K1 and K3.
RX show ip protocols include K EIGRP metric weight K1-0, K2-0, K3-1, K4-0, K5-0
If we want to use all K values:
RX (config) – router eigrp[ASN] RX (config-router) – metric weights[K1] [K2] [K3] [K4] [K5] [K6]
in other words:
RX (config) - router eigrp 10 RX (config-router) metric weights 1 1 1 1 1 1
For two routers to become neighbors, K values must be the same!
The Mathematical Formula
In order to calculate the Metric for each network learned by its neighbours, the EIGRP protocol uses the following formula:
That's a big formula!
Cisco recommends not to touch these criteria so we'll listen to it eh?
If we don't touch the K values, the formula is this:
Bandwitch (in kbps)
Delay – The response time between our router and the network to be reached (in ten microseconds either Delay 100ms – Delay 10)
Consider the following delays and bandwitches:
Let's calculate the best Metric for our routers to join the LAN-21:
- R1: (( 10,000,000 / 100,000 ) – 1.5 ) – 256 – 25,984
- R11: (( 10,000,000 / 100,000 ) – 1 ) – 256 – 25,856
- R12: (( 10,000,000 / 100,000 ) – 1.3 ) – 256 – 25,933
- R13: (( 10,000,000 / 100,000 ) – 1.3 ) – 256 – 25,933
- R14: (( 10,000,000 / 100,000 ) – 1.3 ) – 256 – 25,933
Now that we have our Metric, let's see how it goes in our topological tables (for the rest of the course, I preferred to take simpler examples).
Where are our Metrics stored?
In the topological table
R1 show ip eigrp topology IP-EIGRP Topology Table for AS(10)/ID (22.214.171.124) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 126.96.36.199/24, 1 estates, FD is METRIC via 192.168.12.2 (METRIC / RED-ROR METRIC), FastEthernet0/0
In the routing table
R1- show ip road Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, - candidate U default - per-user static road Gateway of last resort is not set D LAN-21 via 1[90/ METRIC ].1.11.2, 00:01:39, FastEthernet0/11
EIGRP takes into account 5 parameters: Bandwidth, Load, Delay, Reliability and MTU.
Cisco advises not to touch K values.
The Bandwitdh taken into account is the smallest of the link.
The delay is the total time it takes a package to go from point A to point B.
Hoping you enjoyed this article!
Don't hesitate to let me know!!