From: Kenneth Wygand (KWygand@customonline.com)
Date: Sun Jun 20 2004 - 14:55:21 GMT-3
Group,
One "uniform" solution would be to implement a positive number for the preference on the preferred IRDP router and use a negative number for the preference on the non-preferred IRDP router (assuming you only have two routers on the common subnet).
This will ensure the higher/positive number will be the preferred router no matter what the underlying implementation is for preferred router selection (highest decimal number vs. two's compliment).
Ken
-----Original Message-----
From: nobody@groupstudy.com on behalf of Howard C. Berkowitz
Sent: Sun 6/20/2004 11:21 AM
To: ccielab@groupstudy.com
Cc:
Subject: Re: IRDP Very interesting
From RFC 1256 on Router Discovery:
The router discovery messages do not constitute a routing protocol:
they enable hosts to discover the existence of neighboring routers,
but not which router is best to reach a particular destination. If a
host chooses a poor first-hop router for a particular destination, it
should receive an ICMP Redirect from that router, identifying a
better one.
A Router Advertisement includes a "preference level" for each
advertised router address. When a host must choose a default router
address (i.e., when, for a particular destination, the host has not
been redirected or configured to use a specific router address), it
is expected to choose from those router addresses that have the
highest preference level (see Section 3.3.1 in the Host Requirements
-- Communication Layers RFC [1]). A network administrator can
configure router address preference levels to encourage or discourage
the use of particular routers as default routers.
A Router Advertisement also includes a "lifetime" field, specifying
the maximum length of time that the advertised addresses are to be
considered as valid router addresses by hosts, in the absence of
further advertisements.
At 8:06 AM -0700 6/20/04, Tom Rogers wrote:
>Thanx, William.
>Correct me if I read it wrong , even Windows machine prefer lower preference.
>
>Thanx
>Tom
>
>
>William Chen <kwchen@netvigator.com> wrote:
>Hi,
>
>FYI.
>
>
>http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnw2kmag00/html/Redundant2.asp
>
>- William
>
>----- Original Message -----
>From: "Tom Rogers"
>To: "Phil" ; "Richard Anderson"
>;
>Cc: "Tom Rogers" ;
>Sent: Sunday, June 20, 2004 3:25 PM
>Subject: Re: IRDP Very interesting
>
>
>> Very intersting...
>> So IRDP works in 2's compliment. I searched gs and found some interesting
>stuff.
>> In 1st the link Brian Dennis said that ..
>> Preferred router (among 2) is the one with highest # if both values
>are -ve, otherwise it is the lowest value.
>>
>> "So to sum it up don't use a Cisco router as an IRDP client ;-) "
>>
>> What happend if it the client is Windows or a PC?
>>
>> http://www.groupstudy.com/archives/ccielab/200207/msg01128.html
>>
>> http://www.groupstudy.com/archives/ccielab/200210/msg01869.html
>>
>> http://www.groupstudy.com/archives/ccielab/200209/msg00599.html
>> Thanks
>> Tom
>>
>> Phil wrote:
>> Try a search in the archives for "irdp preference". I remember this
>> being discussed in the past.
>>
>> Phil
>>
>> On Sat, 19 Jun 2004 21:39:15 -0700, Richard Anderson
>> wrote:
>> >
>> > Tom,
>> >
>> > I am little confused. I don't know what practice lab has this type of
>> > scenerio with a wierd answer. To me, Preferred router should have a
>higher
>> > preference.
>> >
>> >
>> >
>> > ----- Original Message -----
>> > From: "Tom Rogers"
>> > To:
>> > Sent: Friday, June 18, 2004 10:51 AM
>> > Subject: IRDP
>> >
>> > > I thought I was clear on IRDP, but after reading a solution, it has
>made
>> > me confused.
>> > >
>> > > I went through the doc cd and some books. They say if a router is to
>be
>> > preferred increase the preferece value in it.
>> > >
>> >
>http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr
>> > as_r/1rfipadr.htm#wp1018753
>> > >
>> > > But in a scenario the question is like this.................
>> > >
>> > > R6 is to be preferred as default gateway over R3.
>> > > Solution says, to lower the preference value for R6.
>> > > The solutuon has R6 as iprdp preference= 100 and R3 as 200 and yet
>they
>> > say R6 will be preferred.
>> > > Is this correct? Should'nt it be other way round?
>> > > According to me if R6 is to be preferred it should be 200 and r3 as
>100.
>> > > Can some one throw some light on this.... please..
>> > > What wrong am I thinking....
>> > >
>> > > Tom
>> > >
>> > >
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