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Duplicate MAC addresses on two interfaces

 
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Larry Dillon
Advisor

Duplicate MAC addresses on two interfaces

Greetings,

       I'm seeing the same MAC addresses on two interfaces (AA-00-04-00-03-04), which is not the native hardware MAC addresse of the interfaces ( should be 00-1C-C4-FC-D1-4F and 00-1C-C4-FC-D1-4E)

 

 

LANCP> SHOW CONFIGURATION

MRMC LAN Configuration (24-JUN-2015 10:20:29.30):
         Parent or
  Device  PrefCPU  Medium/User Version  Link  Speed  Duplex Auto BufSize   MAC Address          Type      Description
  ------  -------  ----------- -------  ----  -----  ------ ---- ------- ----------------   ------------  -----------
   EWA0      0      Ethernet    X-99     Up    1000   Full   Yes   1500  AA-00-04-00-03-04  UTP Merl5704
                                                                         00-1C-C4-FC-D1-4F (default)
   EWB0      3      Ethernet    X-99     Up    1000   Full   Yes   1500  AA-00-04-00-03-04  UTP Merl5704
                                                                         00-1C-C4-FC-D1-4E (default)
LANCP> 

 

 

 

OpenVMS 8.4

System:  rx2660

TCPIP V5.7-13

Not in a cluster

 

Long story:

At a site I help manager, the on-site tech enabled the secondary interface and assigned it a unique IP address. This was to address disconnects he was seeing, though I don't believe this is really the right way forward.  I do see some errors on the primary Ethernet interface.  I think that the root cause is probably a bad switch  or switch port.

 

I'm guessing that someone tried to configure something incorrectly (maybe failover, maybe some cluster setting?) and it was never a problem until the second Ethernet interface was configured.

 

I can't find any documented way to reset the Ethernet interfaces to their factory-assigned MAC address.

 

Any help would be appriciated.

3 REPLIES
Volker Halle
Honored Contributor

Re: Duplicate MAC addresses on two interfaces

Larry,

 

this MAC address AA-00-04-00-03-04 is the DECnet Phase IV MAC address of this node. The DECnet Phase IV node address of this node is 1.3 (verify with $ SHOW NETWORK).

 

You need to stop running the DECnet IV protocol on the interface, if you do not want it to change its MAC address to the DECnet Phase IV MAC address, when starting DECnet.

 

Assuming you're running DECnet-OSI, you need to change the following setting in

 

SYS$SYSROOT:[SYSMGR]NET$ROUTING_STARTUP.NCL

...

SET NODE 0 ROUTING CIRCUIT CSMACD-0 ENABLE PHASEIV ADDRESS = TRUE

...

 

Find out which CSMACD station is mapped to EWB0 by looking at

 

SYS$SYSROOT:[SYSMGR]NET$CSMACD_STARTUP.NCL

...

CREATE NODE 0 CSMA-CD STATION CSMACD-0 COMMUNICATION PORT = EWA

...

 

If you've found the CSMACD station number for the desired LAN interface, change PHASEIV ADDRESS = TRUE to FALSE and reboot.

 

Do NOT change this on ALL LAN interfaces, if you are using DECnet Phase IV communication with any other nodes.

 

Volker.

Hoff
Honored Contributor
Solution

Re: Duplicate MAC addresses on two interfaces

DECnet Phase IV or DECnet with Phase IV compatibility is running on a network that's not VLAN'd or segmented.   It's permissible to connect network segments via a DECnet router, but you can't directly connect two interfaces to the same VLAN or same segment.  Either shut off DECnet on the secondary controller, or configure a VLAN or otherwise split the segments.

 

The DECnet Phase IV analog of the Phase V / DECnet-Plus / DECnet OSI commands that Volker references are:

 

$ RUN SYS$SYSTEM:NCP

NCP> SHOW KNOWN CIRCUIT CHAR

NCP> SET CIRC xyz-0 STATE OFF

NCP> SET LINE xyz-0 STATE OFF

NCP> DEFINE CIRC xyz-0 STATE OFF

NCP> DEFINE LINE xyz-0 STATE OFF

 

The first NCP command gives you the names of the circults you're going to need to pick from (xyz-0 is shown, yours will differ), and some general information, while the subsequent four commands disable the DECnet line (interface, physical widget) and circuit (DECnet virtual circuit) in the volatile (SET) and permanent (DEF) databases. 

 

Related:

Intro to MAC addresses on OpenVMS

DECnet Troubleshooting (MAC address section)

IVADDR invalid media address (DECnet Phase IV address collision)

Larry Dillon
Advisor

Re: Duplicate MAC addresses on two interfaces

Thanks so much to Volker and Hoff, the NCP commands resolved the duplicate MAC addresses.

 

I know very little about DECNet. We rarely use it.  We usually run DECnet Plus and this had Phase IV installed by a 3d party, so it was acting dfferently from the rest of our servers.

 

Thanks again.  You guys rock!