3300 ARP/Duplicate ip

[raymk]

ood afternoon,

Could any one help me figure out why our 3300 is complaining about duplicate ip addressing even though there isn't any conflicts



Duplicate IP Address Detector
Description   Possibly 2 computers with the same IP address (172.18.98.116).
One of those computers has MAC address 08:00:0f:54:ac:b8. If this IP is used by
the Mitel RTC card, E2T card, a phone or router, there may be disruption in telephone service.


Time   14:39:17
Source   Duplicate IP Address Detector
Description   Possibly 2 computers with the same IP address (172.18.98.116).
One of those computers has MAC address 00:00:0c:07:ac:02. If this IP is used by
the Mitel RTC card, E2T card, a phone or router, there may be disruption in telephone service.


3300 arp table



LINK LEVEL ARP TABLE
Destination      LL Address        Flags  Refcnt Use        Interface
---------------------------------------------------------------------

172.18.98.116    08:00:0f:54:ac:b8 0x8405 2      1260       motfcc0   ( mitel Handset)

172.18.99.254    00:00:0c:07:ac:02 0x8405 42     0          motfcc0    ( HSRP active virtual Gateway address)


Cisco arp entries for above ips

Internet  172.18.99.254           -   0000.0c07.ac02  ARPA
Internet  172.18.98.116         141   0800.0f54.acb8  ARPA



The pbx system ip info



Host Name   o=motfcc   
System IP Address   172.18.99.200   
Subnet Mask   255.255.254.0   
Gateway IP Address   172.18.99.254   
Layer 2 (L2) Switch IP Address   172.18.99.202   
E2T Card IP Address   172.18.99.201 / 255.255.254.0

Ip routing


ICMP Router Discovery Server   Enabled
Gateway IP   172.18.99.254

As you can see there are no conflicts as such but the 3300 still reporting there is .

Any ideas guys ?


Thanks in advance.

[ralph]

Did you figure out what this device is: 00:00:0c:07:ac:02
It's not a Mitel.  It will be a cisco.
Something there is going on.

Ralph

[raymk]

Hi Ralph,


WE have two cisco switches configured with hsrp redundancy for our vlans.


0000.0c07.ac02  is the  HSRP virtual gateway mac address for our phone system vlan

thanks

Ray

[raymk]

Solved,

Should of spotted this earlier.


the guy who set up the vlan interfaces on our Cisco cat switch has used a wrong subnet mask.  The vlan range was 172.18.98.0/23  98.1 to 99.254  For our voice vlan

The vlan interface was configured as 172.18.99.252/24

When the 3300 controller was arping for any addresses in 172.18.98.0 /23 range it considered them to be in a different subnet  and sent the request to the hrsp default gateway address 172.18.99.254 ( default Behavoir in address is considered on a diff subnet)

HSRP active interface repsonded  with its mac address ( proxy arp) This address was already in the arp cache on the controller as the default gateway address causing the alert to be generated.


Sicne changing the Cisco  cat voice vlan  interface to the correct subnet mask the controller can send arp request to the entire /23 range.

 
No more pesky duplicate ip conflict messages.