From: Sam Joseph (samjoseph747@hotmail.com)
Date: Wed Apr 20 2005 - 14:18:08 GMT-3
you got it. Now. let us hear from what others have to say.
Come on Brian's, Scott's ,etc clear the wind.
Thanks.
>From: "ccie2be" <ccie2be@nyc.rr.com>
>To: "'Sam Joseph'" <samjoseph747@hotmail.com>
>CC: <ccielab@groupstudy.com>
>Subject: RE: ipv6: SLA and subnet ID
>Date: Wed, 20 Apr 2005 11:38:38 -0400
>
>Sam,
>
>Thanks for bearing with me on this.
>
>I think I now understand the first part of your explanation but I'm not
>sure
>about the other part.
>
>In the original question, it was given that a site local address of
>FEC0/125
>should be used. And, in a Site local address, the 16 bits that follow the
>first 48 represent the subnet-id which is why you used this:
>
>FEC0:0:0:D
>
>for the 1st half of the address. OK, this part makes sense.
>
>Now, for the 2nd half of the address. You used the 5th hex grouping for
>the
>SLA. If I understand you're reasoning, the 5th hex didn't have to used.
>The
>6th or 7th hex field could have been used but using the 5th hex field makes
>summarization easier. Do I have that right?
>
>What confused me most about this problem was that I originally thought D
>should be used the way you said. But, the "official" solution swapped the
>position of the subnet id and SLA values. It has this:
>
>FEC0:0:0:B::D:x/125 where x is the router number.
>
>I tend to expect the "official" answers to be correct. But, sometimes, like
>in this case, they aren't.
>
>Thanks again. Tim
>
>
>
>-----Original Message-----
>From: Sam Joseph [mailto:samjoseph747@hotmail.com]
>Sent: Wednesday, April 20, 2005 10:51 AM
>To: ccie2be@nyc.rr.com
>Cc: ccielab@groupstudy.com
>Subject: RE: ipv6: SLA and subnet ID
>
>Tim,
>
>You are getting it on your Last Paragraph. On a Site Local Address (ipv6),
>the first 48 bits (3hex's) are always fixed. That would be FEC0:0:0. The
>Next Portion is 16 Bit Subnet-ID ( 1hex). The Last 64 bits (4hex) is the
>interface ID. This interface ID can be an extension or may also represent
>of
>
>the Subnet. Cisco calls it as concatenation of Subnet ID.
>
>Since in this question, you are specifically told to use Subnet_Id of D, we
>are left with the choice of
>using the 5th hex as site level identifier.
>
>If you ask me, do i have to use only the fifth hex as site level aggregator
>?. The answer is it depends. When you are aksed to summarize it somewhere
>upstream, following an hierachical addressing will be hell a lot easier.
>
>Hope I made sense in this explanation. If any one can improve upon, pls
>come
>
>forward.
>
>Thx.
>
> >From: "ccie2be" <ccie2be@nyc.rr.com>
> >To: "'Sam Joseph'" <samjoseph747@hotmail.com>
> >CC: <ccielab@groupstudy.com>
> >Subject: RE: ipv6: SLA and subnet ID
> >Date: Wed, 20 Apr 2005 08:56:09 -0400
> >
> >Sam,
> >
> >Thanks for getting back to me. I appreciate it.
> >
> >I think your answer is correct but the issue I still have is this:
> >
> >Why did you decide to use
> >
> >FEC0::D:B:0:0:2/125 on R2 and FEC0::D:B:0:0:1/125 on R1
> >
> >instead of, for example,
> >
> >FEC0::B:D:0:0:2/125 on R2 and FEC0::B:D:0:0:1/125 on R1
> >
> >or this:
> >
> >FEC0::D:0:0:B:2/125 on R2 and FEC0::D:0:0:B:1/125 on R1
> >
> >In this task is there one and ONLY one correct answer or many possible
> >correct answers?
> >
> >The trouble I'm having with this problem is that in the Cisco doc's they
> >show examples of ipv6 addresses using a SLA and a subnet ID but never
>both
> >of these fields in the same type of address. And, in the examples, both
>the
> >SLA and subnet ID occupy the same position - bits 49 to 64 from the left
>-
> >in the address.
> >
> >Clearly, its not possible for both the subnet id and the SLA to occupy
>the
> >same bits at the same time in the same type of address. So, why is it you
> >choose to make the subnet, B, part of the interface id and place it where
> >you did?
> >
> >Thanks, Tim
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Sam
> >Joseph
> >Sent: Tuesday, April 19, 2005 9:28 PM
> >To: ccie2be@nyc.rr.com
> >Cc: ccielab@groupstudy.com
> >Subject: RE: ipv6: SLA and subnet ID
> >
> >Hi Tim,
> >
> >How about the following Address:
> >
> >FEC0::D:B:0:0:2/125 on R2 and FEC0::D:B:0:0:1/125 on R1
> >
> >My Explanation:
> >
> >First 48 bits are FEC0:0:0 ( 3hex)
> >Subnet ID is 000D (1 hex)
> >Interface ID is B:0:0:1 (SLA in this case since this is specific to site
>or
> >local to the organization)
> >
> >If any better thoughts, please come forward.
> >
> >Thx,
> >
> >Sam
> >
> > >From: "ccie2be" <ccie2be@nyc.rr.com>
> > >Reply-To: "ccie2be" <ccie2be@nyc.rr.com>
> > >To: "Group Study" <ccielab@groupstudy.com>
> > >Subject: ipv6: SLA and subnet ID
> > >Date: Tue, 19 Apr 2005 18:43:16 -0400
> > >
> > >Hi guys,
> > >
> > >If I'm given this info in the lab, how do I figure out where to put
>what:
> > >
> > >1. All ipv6 addresses will use FEC0/125 unless otherwise specified.
> > >
> > >2. Configure a site-local subnet D between R1 and R2 and use SLA number
> >B.
> > >
> > >
> > >From the Cisco documentation, a site local address has a subnet ID but
> >not
> > >a
> > >SLA. While a global unicast address has a SLA but not a subnet ID.
> > >
> > >Now, I realize that with a netmask of /125, there's lots of room to put
> > >things where I want but if given only the above info, how do I figure
>out
> > >what's OK?
> > >
> > >TIA, Tim
> > >
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