From: Jongsoo.Kim@Intelsat.com
Date: Mon Feb 07 2005 - 18:43:52 GMT-3
Tip
See mine below
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Monday, 07 February, 2005 3:34 PM
To: Kim, Jongsoo; ccielab@groupstudy.com
Subject: Re: ipv6 eui-64 and link-local
Thanks Jongsoo. Please see in-line comments.
----- Original Message -----
From: <Jongsoo.Kim@Intelsat.com>
To: <ccie2be@nyc.rr.com>; <ccielab@groupstudy.com>
Sent: Monday, February 07, 2005 1:36 PM
Subject: RE: ipv6 eui-64 and link-local
> Tim
>
> Here is my answer as I am studying Ipv6 as well.
>
> I think ipv6 address fec0:157:1:14::/64 = ipv6 address fec0:157:1:14::0/64
> SO if you <CR>, then fec0:157:1:14::0/64 is your IPV6 site local address.
***************
Does this mean that the low order 64 bits are 0? (yes) And, if so, doesn't
ipv6
automaticially use eui-64
to do things like find neighbor's link layer address? And, if not, doesn't
that mean we have to always use eui-64?
############# ( this is based on my study so far,)
(If you don't configure Link Local address, it will be auto-assigned using
EUI-64 because then link local address is always required.
In this case of auto assignment, "FE80::" will be network bits and EUI-64
will be host bits.
However, you can manually assign it, which I prefer because it is easy to
remember.
You can create longer network bits ( something like FE80:1::) than FE80:: .
For global unicast addresses( such as site local, 6-to-4, aggregatable), I
think per segment either 1) you can manually configure all host or 2) at
least one manual and the rest of auto-config based on IPv6 router
advertisement sent by manually configured host( router port).
So these are not fully automatic like link local address.
Also you have to configure Auto or manual.
Your below config "Rack1R1(config-if)#ipv6 address fec0:157:1:14::/64 ?" is
manual.
And "Rack1R1(config-if)#ipv6 address autoconfig" is auto-config.
If you do auto-config on 6-to-4 tunnel, then you have to disable the
suppression of router advertisement in manually configured tunnel port by "
no ipv6 nd supress-ra". Otherwise, ipv6 address autoconfig won't work. But
in broadcasting interface like ethernet, RA is not suppressed by default.
################
>
> EUI-64 is based on 24 bits of MAC address + FFFE + 24bit of Mac ADDRESS.
> So if MAC is 0000.0C0A.2C51, then EUI is 0000.0C + FF.FE + 0A.2C51.
> Final IPv6 address will be fec0:157:1:14:0000:0CFF:FE0A:2C51
>
> Link local address is very important when Ipv6 routing protocol is
running.
> It is better to manually configure because it's easy to remember.
> For example, if you running IPv6 OSPF over frame-relay and you have to
> configure frame-relay map,
> you must configure something like " frame-realy map ipv6
link-local-address
> DLCI broadcast".
> In this case, you want to use very easy link-local address such as
"FE80::1"
>
>
> Regards
>
>
> Jongsoo
>
>
>
> -----Original Message-----
> From: ccie2be [mailto:ccie2be@nyc.rr.com]
> Sent: Monday, 07 February, 2005 8:21 AM
> To: Group Study
> Subject: ipv6 eui-64 and link-local
>
>
> HI guys,
>
> I'm very unclear about when I need to use the eui-64 or link-local options
> when configuring an ipv6 address.
>
> For example, what's the difference between the following 2 options?
>
>
> Rack1R1(config-if)#ipv6 address fec0:157:1:14::/64 ?
> eui-64 Use eui-64 interface identifier
> <cr>
>
> If I just hit enter <cr>, what will be the value of the low 64 bit's?
>
> Also, regarding the link local option, I understand that ipv6 will
> automatically generate a link-local address from the site local or the
> aggregatable global unicast address. So, why would I ever want to
override
> the auto generated link-local address?
>
> Thanks for your help. I'm really struggling with this ipv6 stuff.
>
> Tim
>
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