*TechNotes* EIGRP

Webmaster

Here is the first in our BSCI TechNotes series:

Enhanced IGRP *NEW*

Let me know if you have any comments or suggestions, requests, anything...

Johan

blesa

Well,

I have a question regarding EIGRP.
let say that we run
R2#show ip eigrp topology

and we get:
...
P 20.20.20.0/24, 1 successors, FD is 1889792
via 10.10.10.1 (1889792/128256), Serial 2/0.1
....

What is 128256?
Also what the code P-Passive means? A-Active?
Thanks in advnace.

B.A.

blesa

Hi,

I failed to understand when we use command

metric weight tos K1 K2 K3 K4 K5

what is connection with Ks and bandwidth, delay, reliability, load and MTU? Is K1= bandwith and so forth?
Well when I look at the formula to calculate the composite metics, I am not sure which K variable should be used for MTU and for delay?
Ok, tos is Type of Service and must be 0? Ok, but then why do we need tos in our formula when it is always 0?

I do realise that each constant is used to assign a weight to a specific variable.

Second question is when the folowing command will all of th erouters that the router has formed neighbours with:
R2#show ip eigrp neighbor
...

Now we have a coloumn as RTO and SRTT. What is actually SRTT and RTO?

Thanks in advance


Blesa

kemot

P means stable
A means that DUAL is working
(1889792/128256), (Fiseable distance/Reported distance)

Am I Right?

:P Tom

blesa wrote:

Well,

I have a question regarding EIGRP.
let say that we run
R2#show ip eigrp topology

and we get:
...
P 20.20.20.0/24, 1 successors, FD is 1889792
via 10.10.10.1 (1889792/128256), Serial 2/0.1
....

What is 128256?
Also what the code P-Passive means? A-Active?
Thanks in advnace.

B.A.

kemot

AFAIK:

tos=0 nobody knows

SRTT - Smooth Round Trip Timer
RTO - Retransmission Time Out

Tom

blesa wrote:

Hi,

I failed to understand when we use command

metric weight tos K1 K2 K3 K4 K5

what is connection with Ks and bandwidth, delay, reliability, load and MTU? Is K1= bandwith and so forth?
Well when I look at the formula to calculate the composite metics, I am not sure which K variable should be used for MTU and for delay?
Ok, tos is Type of Service and must be 0? Ok, but then why do we need tos in our formula when it is always 0?

I do realise that each constant is used to assign a weight to a specific variable.

Second question is when the folowing command will all of th erouters that the router has formed neighbours with:
R2#show ip eigrp neighbor
...

Now we have a coloumn as RTO and SRTT. What is actually SRTT and RTO?

Thanks in advance


Blesa

gencoyilmaz

Webmaster wrote:

Here is the first in our BSCI TechNotes series:

Enhanced IGRP *NEW*

Let me know if you have any comments or suggestions, requests, anything...

Johan

Hi,
in this BSCI technotes there is a section about route summarization and the command for summarization is shown as:

router(config-if)#ip summary-address as-number network-address subnet-mask [admin-distance]

I think there must be an "eigrp" word before as-number
Am I right ?

Webmaster

Yes, you are absolutely right.

It should indeed be

router(config-if)#ip summary-address eigrp as-number network-address subnet-mask [admin-distance]

I will correct it immediately. Thanks for spotting that one and letting me know.

Johan

smashingguy

R2#show ip eigrp topology

and we get:
...
P 20.20.20.0/24, 1 successors, FD is 1889792
via 10.10.10.1 (1889792/128256), Serial 2/0.1

For the above output, I saw an explanation for the value 1889792 in (1889792/128256), but is 128256 the AD(Administrative distance). Jus wonderin if it is a composite metric. Can anyone confirm??

EdTheLad

In the technote it says max hop counts for eigrp is 224, on cisco white papers it says 220 and in kplabs sample chapter it says 255.What is it?
I would go with 220 myself!!

Webmaster

I stick to my 224. Below are some links:

Cisco.com

Google (Check out nr3 )

Page 14 of this PDF from Cisco Press

ed_the_lad wrote:

on cisco white papers it says 220

Do you have a link? I'm curious why cisco would list 220...

255 is the maximum configurable hopcount (network diameter actually)for IGRP, by default it's 100.

EdTheLad

Eigrp whitepaper http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml#metrics

Contains the following passage:

Hop count is 2 This is not used in metric calculations, but does limit the maximum size of an EIGRP AS. The maximum number of hops that EIGRP will accept is 100 by default, although the maximum can be configured to 220 with metric maximum hops.

Now i know its configurable to 255 but do they mean it will only allow 220 or maybe its a typo as youve seen 224 stated in a couple of places.This doc was
last updated: Sep 09, 2005.

cisco_trouble

Hi there people,

Whats the purpose of manipulating the eigrp metrics? i assume they affect the whole network and are not locally significant?

Thanks

EdTheLad

The weights are locally significant but they must be the same as your neighbor if you want an adjacency formed.Its advisable to have the same weights everywhere in the network.
Not recommended to change the weights unless you really need, the reason to change is to have more granularity in your routing metric.

bina

hi
your EIGRP technote is very good and useful.Will u please put more notes on other topics of CCNP like OSPF,BGP,IS-IS (from CCNP BSCI)
and also for other CCNP modules.I'll be looking forward for more notes on CCNP
thankx

Spider007

thanks

Paul Boz

Thank you Johan, this guide is very concise and full of information

LordFlasheart

Hi,

When you run

show ip protocols

you should see the K values, by default, set to 10100. Where there is a 1 is when that element is used to calculate the metric. By default EIGRP uses bandwidth and delay so that is where the two 1's come in.

The K values are:

K1 = Bandwidth
K2 = Load
K3 = Delay
K4 = Reliability
K5 = MTU

However, when you configure redistribution into EIGRP the order of the metrics is (somewhat confusingly) different. It is Bandwidth, Delay, Reliability, Load, MTU.

HTH,

Chris[/code]