RE: ipv6 addressing question for subnetting...

From: Scott Morris (swm@emanon.com)
Date: Fri Sep 23 2005 - 14:32:32 GMT-3


According to the spec for Site Local Addressing, you would use a /64 mask.
If there's a further requirement (for whatever reason) to make a network
where only 8 hosts are allowed, then a /125 may be more appropriate. But
the /125 is no more right or wrong than your /80 mask!

HTH,

Scott
 

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Edwards, Andrew M
Sent: Friday, September 23, 2005 1:08 PM
To: ccielab@groupstudy.com
Subject: Re: ipv6 addressing question for subnetting...

Sounds like a dumb question but here goes.

I was working on a vendor lab.

The requirement was to address interfaces over frame using site-local
addressing.
Use an SLA of B. All hosts are on subnet 2A. Use the router id as the host
IP.

The answer key used:

FEC0::B:0:0:2A:1/125
FEC0::B:0:0:2A:3/125
FEC0::B:0:0:2A:2/125

My thoughts:

The SLA is known as a 16 bit value before host-id. We also know site-local
addressing FEC0:/10 is defined.

So I have no qualms with: FEC0::B.....

If the subnet is just a masked off portion of the host id like in IPv4,
would there be a problem in using the following subnets?

FEC0::B:2A:0:0:1/80
FEC0::B:2A:0:0:3/80
FEC0::B:2A:0:0:2/80

Granted, my alternative answer is a larger single subnet, but aren't they
basically the same?

Just looking to make sure I understand V6 subnetting because their answer
threw me... I was under the impression that last 64 bits were all for the
host and SLA/subnetID was for subnetting. Their answer key made me rethink
this understanding to mean that I could use the SLA bits for subnetting and
I could further subnet within the host bits portion of the v6 address space.

Thanks in advance,

andy



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