Subject: VRRP and DECnet

From: Carol Iturralde <[email-masked]>
Date: Fri, 10 Apr 1998 14:17:31 -0400

Bringing DECnet up on an interface (e.g., Ethernet or FDDI) 
causes the MAC address to be modified.  DECnet sets it to
a desired value -- and it must use this value.

It occurs to me that this means that VRRP and DECnet cannot
be running on the same interface (unless the interface is
smart enough to use one MAC address for DECnet packets,
and a different one for IP packets, which most aren't).

Should the VRRP spec. say something about how it may not
be implementable to run DECnet and VRRP on the same
interface?

---

From: Peter Hunt <[email-masked]>
Date: Fri, 10 Apr 1998 11:35:42 -0700

> a desired value -- and it must use this value.

Is this a problem with sending or receiving packets? That is, must DECnet
packets be use the DECnet MAC as their source MAC? Or do you see this as
a problem in receiving packets (ie. the ethernet device can't filter on
both the DECnet MAC and the VRRP MAC at the same time)?

	Regards,

	Peter.

---

From: Bob Hinden <[email-masked]>
Date: Fri, 10 Apr 1998 11:46:11 -0700

Carol,

>be implementable to run DECnet and VRRP on the same

Probably not.  Same issue come up with running Decnet and IP (independent
of VRRP), IPX, CLNP, etc. on the same interface.  It would too hard to have
every IP related specification have to specify the complications of running
it with every other non-IP protocol.

Also, I would think that if one can run Decnet and IP on the same
interface, then this shouldn't be too much of a problem.  

Bob

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From: Rob Montgomery <[email-masked]>
Date: Fri, 10 Apr 1998 15:36:33 -0400

Not to beat a dead horse, but shouldn't this be a warning about what
happens when layer 3 protocols start messing around with the MAC
address. (hint, hint, hint.) :-)

-Rob

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From: Carol Iturralde <[email-masked]>
Date: Mon, 13 Apr 1998 08:51:04 -0400

Peter:

You are correct -- this is not the problem I thought it was.
The vrrp-router could receive both the DECnet MAC address
and the VRRP MAC address at the same time (or at least in
my implementation it can).

Thanks for the response.  I withdraw the issue -- it is not
really an issue.

Carol

---

From: Peter Hunt <[email-masked]>
Date: Mon, 13 Apr 1998 08:12:38 -0700

Carol,

> my implementation it can).

It may be device dependent; some ethernet devices allow additional
unicast MAC address filters to be configured, so the physical,
DECnet and VRRP MAC addresses can all coexist. DEC tulip devices
allow this, for example.

Some devices may not support this, but you can always work around
it by putting the device in promiscuous mode and filtering in
software. Not ideal, I'll grant you. :)

But I agree that the issue doesn't merit updating the draft.

Regards,
-- 
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