From: Dapeng Guo (dapengguo@xxxxxxxx)
Date: Thu Jan 18 2001 - 21:32:18 GMT-3
My understanding is that by default, the metrics of IGRP/EIGRP are only
calculated by BW and DLY. In the case of a tie, IGRP/EIGRP do load balance.
Only when 'metric weight tos k1 k2 k3 k4 k5'(default k1=k3=1, k2=k4=k5=0) is
configured others are taken into account.
Dapeng Guo
----- Original Message -----
From: Alan Basinger <abasinge@swbell.net>
To: 'CCIE newsgroup (E-mail)' <ccielab@groupstudy.com>
Sent: Thursday, January 18, 2001 11:27 AM
Subject: RE: Metrics when redistributing.
> I think if I am not mistaken I read that bandwidth and delay are the 2
> primary values used in calculating path selection but in the event of a
tie
> in those values the remaining values are considered?
>
> Alan Basinger
> Systems Engineer
> SBC DataComm
> Houston Texas
> abasinge@swbell.net
>
> | |
> ||| |||
> .|||||. .|||||.
> .:|||||||||:.:|||||||||:.
> C i s c o S y s t e m s
> Certified Gold Partner
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Chuck Larrieu
> Sent: Thursday, January 18, 2001 10:14 AM
> To: Schmitt, Greg; 'CCIE newsgroup (E-mail)'
> Subject: RE: Metrics when redistributing.
>
>
> I believe the experiment I detail below indicates that in effect it does
> not matter. (E)IGRP metric is bandwidth and delay, unless you physically
go
> in and change them. My experiment indicates that even though the
> redistribution command requires numbers, the default calculation ignores
> those values.
>
> Chuck
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Schmitt, Greg
> Sent: Thursday, January 18, 2001 5:30 AM
> To: 'Chuck Larrieu'; 'Alan Basinger'; 'Virnoche, Phil'; 'CCIE newsgroup
> (E-mail)'
> Subject: RE: Metrics when redistributing.
>
> Greetings,
>
> Just watching this thread, and Alan is correct, you have the load and
> reliability switched here. It's probably a typo, but I
> wouldn't want any newbies to get confused here.
>
> I can't imagine you would ever want to have your load setting maxed out
> (255) and your reliability set to the min. Here is
> the explaination of the igrp metric settings from the ios:
>
> r5(config-router)#router ig 10
> r5(config-router)#redis os 10 met ?
> <1-4294967295> Bandwidth metric in Kbits per second
>
> r5(config-router)#redis os 10 met 10000 ?
> <0-4294967295> IGRP delay metric, in 10 microsecond units
>
> r5(config-router)#redis os 10 met 10000 10 ?
> <0-255> IGRP reliability metric where 255 is 100% reliable
>
> r5(config-router)#redis os 10 met 10000 10 255 ?
> <1-255> IGRP Effective bandwidth metric (Loading) where 255 is 100%
> loaded
>
> r5(config-router)#redis os 10 met 10000 10 255 1 ?
> <1-4294967295> IGRP MTU of the path
>
> r5(config-router)#redis os 10 met 10000 10 255 1 1500 ?
> match Redistribution of OSPF routes
> metric Metric for redistributed routes
> route-map Route map reference
> <cr>
>
> So, the normal setting for an ethernet port would be someting like:
>
> redis os 10 met 10000 10 255 1 1500
>
> Cheers,
>
> Greg Schmitt
>
> Internetwork Solutions Engineer
> ThruPoint, Inc. (formerly Total Network Solutions)
> Voice: 410-349-9772
> Cell: 443-822-5183
> Pager: 888-773-0423 or pager.gschmitt@thrupoint.net
> e-mail: GSchmitt@thrupoint.net
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Chuck Larrieu
> Sent: Wednesday, January 17, 2001 10:17 PM
> To: Alan Basinger; Virnoche, Phil; CCIE newsgroup (E-mail)
> Subject: RE: Metrics when redistributing.
>
>
> Ya got me. Some things I think it better to just be a monkey. The command
> calls for numbers. Use standard easy to remember numbers.
>
> Slattery seems to prefer the load = 255 and the reliability = 1
>
> Just before Thanksgiving I posted the following results of an experiment I
> did ( posted to the regular groupstudy list ) I dug it out and here is
what
> I found at that time:
>
> ---------------------
> begin the previous post
>
> Bandwidth Delay Load Reliability MTU resulting route metric
> 1000 100 255 255 1500 12,100
> 1000 50,000 255 255 1500 62,000
> 1000 100 255 1 1500 12,100
> 1000 100 1 255 1500 12,100
> 1000 100 1 255 1 12,100
> 2000 100 1 255 1 8,576
>
> it would appear, then, that ( as we have been told by Cisco ) that only
> bandwidth and delay are the driving force in determining the route metric.
> Slattery's book contains a formula for calculating the metric, but I can't
> get the numbers to match up. There seems to be a constant of 11,000 that I
> can't account for. And while it is intuitively clear that higher
bandwidth,
> as configured in the last line of the table, should lead to a lower
metric,
> I would expect that twice the bandwidth would result in half the metric,
not
> 2/3's of it.
>
> EIGRP works in a similar manner, so I presume that the calculations are
> roughly the same, and that the load, reliability, and MTU factors are of
no
> import, unless one has manually changed the K values using the metric
> weights command.
>
> Hmmmm..... now that's interesting. I thought these values had to match on
al
> routers in the AS. Just changed the defaults on one router, and all routes
> are still appearing, even after multiple clear ip route * commands.
> --------------------
> end of previous post
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Alan
> Basinger
> Sent: Wednesday, January 17, 2001 6:28 PM
> To: Chuck Larrieu; Virnoche, Phil; CCIE newsgroup (E-mail)
> Subject: RE: Metrics when redistributing.
>
> Chuck isn't it 1 load (min) and 255 reliability (max). That usually is the
> case in most scenarios and in most of the information I have read
including
> EIGRP network design. I would assume you would need to know the metrics of
> the protocol your distributing from and to? Also it depends on if you want
> to manipulate which routes or paths are preferred in that particular
routing
> protocol. For example. In rip you inject a route that is 10 hops away but
> adjust the metrics to make it appear 2 hops away to RIP so RIP will use
the
> T3 instead of the 56k link. (This is probably not something one would want
> to do without understanding the consequences of an adjustment like this
but
> you get the idea). I know in BGP you use these to manipulate path
selection
> and can do the same in IGP's. But then I could be completely wrong :) Hope
> this helps.
>
>
> I have pulled my hair out many a night trying to memorize and understand
the
> metrics and how they effects path selection for all the routing protocols
> and decided screw it I'd rather just look them up haha. Now if I could
only
> find them all in one place on the doc CD life would be grand. Can any of
you
> out there help on that one??
>
> Alan Basinger
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Chuck Larrieu
> Sent: Wednesday, January 17, 2001 4:51 PM
> To: Virnoche, Phil; CCIE newsgroup (E-mail)
> Subject: RE: Metrics when redistributing.
>
>
> The Slattery / Burton book Advanced IP Routing in Cisco Networks is a bit
> better in explaining things. While both Slattery and Caslow, in many
> instances, assume far more background than does Doyle, in some cases
> Slattery offers some very good examples and discussion.
>
> A couple of comments below:
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Virnoche, Phil
> Sent: Wednesday, January 17, 2001 11:19 AM
> To: CCIE newsgroup (E-mail)
> Subject: Metrics when redistributing.
>
>
> Question: When redistributing routes into OSPF and EIGRP, how does one
> determine the metrics to use? Is there any good documention that exists
that
> eplains this?
>
> CL: in terms of good practice, one should probably not be too fancy, but
> should stick with accurately representing the network topology However,
> experienced engineers do use metrics to manipulate or otherwise influence
> routing policy.
>
> Caslow's book only says that it is necessary to provide metrics but is
very
> lacking on how these are determined.
>
> FOR EXAMPLE:
>
> router eigrp 1
> redistribute static metric 10000 100 255 1 1500
>
> CL: this places static routes into the EIGRP routing process, and
attributes
> to them an EIGRP metric based on 10 megabits bandwidth, 100 microsecond
> delay, a load of 255 ( max ) a reliability of 1 ( minimum ), and an MTU of
> 1500 bytes If you are in to self inflicted pain, you can use these numbers
> to calculate what shows up in the routing table in the metric column.
>
> router ospf 1
> redistribute eigrp 96 metric 20 metric-type 1 subnets
>
> CL: this places EIGRP originated routes into the OSPF process as external
> type 1 routes ( as the route passes through the OSPF domain, OSPF metrics
> are added to the redistribution assigned metric of 20 ) and all subnets
are
> passed into the OSPF domain as well. ( as opposed to a summary, or not at
> all if you omit the "subnets" keyword. ) In OSPF the metric is cost, which
> in turn is 10^8 / bandwidth. The metric of 20 means the administrator is
> telling OSPF to consider the EIGRP originated routes as the equivalent of
a
> 5 megabit line, or a bit more than three T1's.
>
>
> Danka !
>
> Philip G. Virnoche CCNA
> Network Engineer - AT&T Wireless
> phone: 425.580.5239
> cell: 206.601.3134
>
> "HAM AND EGGS - A day's work for a chicken; A lifetime commitment for a
> pig."
>
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