From: simon hart (simon.hart@btinternet.com)
Date: Sat Apr 02 2005 - 10:10:09 GMT-3
Hi Tim,
Yes you are right, I must say I had not thought of the impact that a change
a MAC address would have on frame map statements. I guess this would be
equally true of dialer map's, again I believe that a dialer interface will
choose from a pool of mac addresses for dynamic IPv6 address creation.
I really does seem that one should stay clear of eui-64 unless explicitly
requested to configure it.
A subsequent question, If for example you're asked within the lab to assign
the address 2001:1234::/64, would you loose points for not using eui-64 but
assign an address yourself? Obviously if you asked to configure
2001:1234::2/64 then you know to ignore eui-64, but for the first case I am
unsure.
TIA
Simon
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: 02 April 2005 14:01
To: 'simon hart'; 'Group Study'
Subject: RE: IPv6 Extended Universal Identifier (EUI-64)
Hi Simon,
A while back, I had wondered about the same thing. Check the GS archives
from February and Andrew Edwards.
I can't remember all the details (Sorry, I have a leaky bucket for a brain)
but, here's the gist of what I do recall.
DON'T USE THE EUI-64 IN COMBO WITH STATIC MAPS
The reason for this is as follows:
Assume on R1 you've correctly configured a f/r static map pointing to R2 and
vice versa and you had used the eui-64 option on both R1 and R2.
You test it and everything works fine i.e. you have connectivity between R1
and R2 over the f/r link.
Recall also that when static maps are configured over f/r, you actually
configure 2 static maps for each destination: 1 to the ipv6 global address
and another one to the ipv6 link local address.
With the static map pointing to the link-local address, you have a static
map pointing to a dynamically created address (because of the eui-64
option.)
Now, let's assume R2 is rebooted. What assurance do you have that R2 will
use the same mac address as before when it reboots?
It's my understanding (which could be faulty) that the mac address used by
the eui-64 option comes from a pool of mac addresses on the router and when
the router reboots, it could (for reasons unknown to me) pick a different
mac address when it reboots.
If this happens, your static map on R1 will no longer be pointing to the
current link-local address on R2. So, now you won't have connectivity any
more.
HTH, Tim
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
simon hart
Sent: Saturday, April 02, 2005 2:12 AM
To: Group Study
Subject: IPv6 Extended Universal Identifier (EUI-64)
Hi Group,
As I understand it, the EUI-64 argument at the end of an IPv6 address
statement will create an IPv6 address based upon the Mac address of the
interface applied.
Now what I need clarity on, is when would you not use the EUI-64 argument?
Simon
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