[Info-vax] Changed MAC addr: Was: tcpip gateway question

[Anton Shterenlikht]

On Tue, Sep 08, 2009 at 09:56:26AM -0700, jbriggs444 wrote:
> On Sep 8, 9:25?am, Anton Shterenlikht <me... at bristol.ac.uk> wrote:
> [snip me asking about duplicate IP address]
> > I don't think so. This ip address has been with this interface for
> > several years now (it was a stand-alone box). Running nmap 137.222.187.238
> > from other boxes doesn't find any other nodes.
> 
> As a stand-alone box it had just the single interface active?  Or
> both?  And was the 137.222.187.238 interface working for TCP/IP
> previously.

This VMS alpha node has 2 interfaces active:

   1  -  WE0 Menu (EWA0: TwistedPair 100mbps)
   2  -  137.222.187.238/24  mech-cluster238       Configured,Active

   3  -  WE1 Menu (EWB0: TwistedPair 100mbps)
   4  -  10.10.10.1/24       vav                   Configured,Active

Yes, 137.222.187.238 was working fine under FreeBSD previously.

> 
> There is a possible hair-brained diagnosis that has occurred to me.
> What if both the front-side and back-side cables are connected to the
> same VLAN or if the front-side and back-side VLANs are somehow cross-
> connected elsewhere.  That kind of misconfiguration would be largely
> symptom-free.

I'm sorry, but I don't understand this..

I just noticed that the MAC address which my networks manager registered
for this ip address (137.222.187.238) has been changed:

 $ show dev ewa0 /full

Device EWA0:, device type DE500, is online, network device, error logging is
    enabled, device is a template only.

    Error count                    5    Operations completed                  0
    Owner process                 ""    Owner UIC                      [SYSTEM]
    Owner process ID        00000000    Dev Prot              S:RWPL,O:RWPL,G,W
    Reference count                0    Default buffer size                 512

Operating characteristics: Link up, Full duplex, Autonegotiation.

    Speed (Mbits/sec)            100
    Def. MAC addr  00-10-64-30-FA-F8    Current MAC addr      AA-00-04-00-06-08

 $

The ip address 137.222.187.238 is registered on
the default MAC address 00-10-64-30-FA-F8.

If the system somehow assigned another MAC addr to EWA0, then it wouldn't
be accepted by the Uni network, and, of course, no tcp/ip connection
on this ip is possible.

But why would the system change the default MAC addr for EWA0?

-- 
Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
University Walk, Bristol BS8 1TR, UK
Tel: +44 (0)117 331 5944
Fax: +44 (0)117 331 5924