From: Ed Lui (edwlui@gmail.com)
Date: Tue Apr 05 2005 - 23:44:14 GMT-3
If I remember correctly. The default eigrp hop count is 100, 255 is
the maximun value. I don't mind to lab it up tonight.
:-)
Edward
On Apr 5, 2005 4:01 PM, John Matus <john_matus@hotmail.com> wrote:
> i was under the impression, from what i have read in the past, that eigrp
> actually does consider a metric of 255 to be unreachable <hops that is>. in
> that situation i suppose you could use an offset list with a metric of 255,
> but mani seems to say differently.
> does anyone else recall eigrps hop limitations?
>
> >From: "ccie2be" <ccie2be@nyc.rr.com>
> >To: "'simon hart'" <simon.hart@btinternet.com>, "'John Matus'"
> ><john_matus@hotmail.com>, <ccielab@groupstudy.com>
> >Subject: RE: blocking eigrp routes
> >Date: Tue, 5 Apr 2005 18:55:08 -0400
> >
> >Simon,
> >
> >I missed that. The doc-cd does say the value is added to the delay
> >component although not where you would expect it to say so. It's in
> >explanation of the example, not where they define what each variable of the
> >command does. Oh, well.
> >
> >As far as where to use this command, I did think of one scenario:
> >
> >Let's say you have to configure equal cost load-balancing and you're
> >prohibited from using any interface commands.
> >
> >To be sure, not a real world scenario, but not too unlikely a Cisco lab
> >task.
> >
> >What do ya think?
> >
> >Tim
> >
> >-----Original Message-----
> >From: simon hart [mailto:simon.hart@btinternet.com]
> >Sent: Tuesday, April 05, 2005 6:40 PM
> >To: ccie2be; 'John Matus'; ccielab@groupstudy.com
> >Subject: RE: blocking eigrp routes
> >
> >Tim,
> >
> >The Doc-CD does provide a hint
> >
> >http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr
> >rp_r/1rfeigrp.htm#wp1022565
> >
> >'For IGRP the offset is added to the delay component only'
> >
> >Now my assumption is that this is what also happens with EIGRP. If I get a
> >chance, and remember when I boot up my routers, I will test to see. With
> >that said, the offset will only be able to adjust one of the components for
> >the reasons stated before.
> >
> >When would you use eigrp offset ??? I am not sure either, have not seen up
> >come up as a requirement.
> >
> >Simon
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> >ccie2be
> >Sent: 05 April 2005 23:17
> >To: 'simon hart'; 'John Matus'; ccielab@groupstudy.com
> >Subject: RE: blocking eigrp routes
> >
> >
> >Simon,
> >
> >How interesting.
> >
> >Unfortunately, but as usual, the Doc-CD sheds no light on this. Did you
> >discover this by testing?
> >
> >I'm still trying to think of a scenario where using the offset command is
> >the only way to achieve the required result, but can't think of any.
> >
> >Have you come across any eigrp scenario's which would require this command
> >to be used?
> >
> >Tim
> >
> >-----Original Message-----
> >From: simon hart [mailto:simon.hart@btinternet.com]
> >Sent: Tuesday, April 05, 2005 6:05 PM
> >To: ccie2be; 'John Matus'; ccielab@groupstudy.com
> >Subject: RE: blocking eigrp routes
> >
> >Tim,
> >
> >I believe the offset is added to the delay component. The offset cannot be
> >the composite metric as the TLV's that eigrp advertised do not include the
> >composite value, but the delay, bandwidth, MTU, Load and Reliability (MTU
> >not used though!!). This is why the K values have to be the same througout
> >the domain.
> >
> >Now what I said below is was slightly incorrect (whoops!!). If the
> >originating route has a delay function of 1000, an offset list of 255 will
> >in fact add 255 to that delay function, thus the delay will now be
> >advertised as 1255 to the next hop.
> >
> >Simon
> >
> >
> >
> >-----Original Message-----
> >From: ccie2be [mailto:ccie2be@nyc.rr.com]
> >Sent: 05 April 2005 22:50
> >To: 'simon hart'; 'John Matus'; ccielab@groupstudy.com
> >Subject: RE: blocking eigrp routes
> >
> >
> >Hi Simon,
> >
> >Excellent post!!!!
> >
> >But, you raise an interesting question.
> >
> >Given that eigrp has 2 types of metrics: bandwidth, delay, etc, and
> >composite, I assume that the metric used with the offset command is the
> >composite version, right?
> >
> >Now, normally with eigrp, whenever you manipulate metric values you're
> >manipulating the component (b/w, delay, etc,) values of the metric, not the
> >composite itself. So, what happens to the component values when you
> >manipulate the composite instead of the component values?
> >
> >Does eigrp use it's formula for computing the composite metric in reverse
> >when the composite itself is changed?
> >
> >Also, given what you've said, it seems like there's no good reason for
> >using
> >the offset-list command with eigrp.
> >
> >If you wanted or needed to change Eigrp's metric, for example, for the
> >purpose of load-balancing, you would change one of the component metrics
> >such as bandwidth or delay on the interfaces to do so rather than
> >manipulate
> >the composite metric with the offset command.
> >
> >So, what reason might there be for using the offset command?
> >
> >TIA, Tim
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> >simon hart
> >Sent: Tuesday, April 05, 2005 5:04 PM
> >To: John Matus; ccielab@groupstudy.com
> >Subject: RE: blocking eigrp routes
> >
> >Hi John,
> >
> >You cannot use the offset list to make a route(s) unreachable with eigrp,
> >although you can do this with rip.
> >
> >Rip has the philosophy that an infinite metric......anything over 15.....
> >is
> >unreachable, therefore making the metric 16 effectively makes those routes
> >effected by the offset list unreachable.
> >
> >Eigrp does not have the same philosophy, the composite metric in eigrp can
> >be anything and as far as the protocol is concerned it is still reachable
> >(within the confines fo FD's and FS's etc. etc.)
> >
> >The example you have given in RIP environment would dictate that every
> >route
> >advertised out of that interface would unreachable (bearing in mind that
> >you
> >could not use 255 in RIP, it would have to be 16). This really would seem
> >a
> >little pointless, may as well make the interface passive.
> >
> >If you used the example below for eigrp you would be advertising eigrp with
> >a metric of 255, and probably making those routes the most favourable.
> >Eigrp uses a composite metric, derived by default as function of bandwidth
> >and delay. The metrics are normally quite high, in fact a lot higher than
> >255 (for information the highest eigrp figure you can use on the offset
> >list
> >is 2147483647).
> >
> >In order not to advertise to the next hop router you could use:
> >
> >router eigrp 100
> >distribute-list 10 out s0/0
> >
> >access-list 10 deny 0.0.0.0 255.255.255.255
> >
> >Change the access list if you wish to deny a subset of routes.
> >
> >HTH
> >
> >Simon
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> >John Matus
> >Sent: 05 April 2005 21:30
> >To: ccielab@groupstudy.com
> >Subject: blocking eigrp routes
> >
> >
> >if i wanted to block all eigrp routes from exiting to the next hop would it
> >be:
> >
> >offset-list 1 out 255 s0/0
> >
> >access-l 1 permit 0.0.0.0 255.255.255.255 ?
> >
> >i wasn't sure since rip's metric would be '16' for offset but i'm not sure
> >about eigrp.
> >thanks in advance
> >
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