MAC address has changed

[Manuel_Pineda]

Hello all,

I am constantly receiving in the log of a CORE-SWITCH S4 this log:

<165>Mar 4 10:26:52 172.16.50.17 RtrArpProc[4]MAC address for 172.16.50.118 has changed from 00-0b-ab-55-a5-1e to 00-0b-ab-55-cb-d4 [ARP rcvd on: ge.4.17]<165>Mar 4 10:37:32 172.16.50.17 RtrArpProc[4]MAC address for 172.16.50.118 has changed from 00-0b-ab-55-a5-1e to 00-0b-ab-55-cb-d4 [ARP rcvd on: ge.4.17]
<165>Mar 4 10:41:49 172.16.50.17 RtrArpProc[4]MAC address for 172.16.50.118 has changed from 00-0b-ab-55-a5-1e to 00-0b-ab-55-cb-d4 [ARP rcvd on: ge.4.17]
<165>Mar 4 10:43:56 172.16.50.17 RtrArpProc[4]MAC address for 172.16.50.118 has changed from 00-0b-ab-55-a5-1e to 00-0b-ab-55-cb-d4 [ARP rcvd on: ge.4.17]
<165>Mar 4 10:48:13 172.16.50.17 RtrArpProc[4]MAC address for 172.16.50.118 has changed from 00-0b-ab-55-a5-1e to 00-0b-ab-55-cb-d4 [ARP rcvd on: ge.4.17]

checking the MAC Address I learned which port are they:

SWS4.CORE1(rw)->sh mac address 00-0b-ab-55-a5-1e
MAC Address FID Port Type Status
----------------- ---- ------------- ------- -------
00-0B-AB-55-A5-1E 40 tg.3.101 learned
00-0B-AB-55-A5-1E 60 tg.3.101 learned

SWS4.CORE1(rw)->sh mac address 00-0b-ab-55-cb-d4

MAC Address FID Port Type Status
----------------- ---- ------------- ------- -------
00-0B-AB-55-CB-D4 40 ge.4.17 learned

SWS4.CORE1(rw)->sh arp
FLAGS: U = Unresolved S = Static
L = Local V = VRRP
* = Stale B = Best Guess Interface

IP Address Hardware Address Flg Age Updated Interface Port
--------------- ----------------- --- ---------- ------- ----------- --------
172.16.50.113 00-0b-ab-55-cb-d4 30d16h35m 0m vlan.0.40 ge.4.17
172.16.50.114 00-0b-ab-55-a5-1e 30d16h35m 0m vlan.0.40 tg.3.101
172.16.50.118 00-0b-ab-55-a5-1e 30d15h18m 0m vlan.0.40 tg.3.101

172.16.50.118 ---> tg.3.101

172.16.50.113 ---> ge.4.17

checking the status of those ports, I noticed that are both as "up":

SWS4.CORE1(rw)->sh port status
Port Alias Oper Admin Speed Duplex Type
(truncated) Status Status (bps)
------------ ---------------- -------- ------- ------ ------- ------------------
tg.3.101 INTER_S4_10G up up 10.0G full 10g-c03 other
ge.4.17 DataPowerSOA1_IP up up 1.0G full 1000-t rj45

So, my question is: are there in some kind of loop?
I understand that a port with spanning tree (or equivalent) is when a port is in state "dormant", isn't it?

How can I solve this situation about this log message?

Thanks in advance.

Manuel.

[mp2014]

what are these devices? cluster? floating virtual ip?

[Bill_Handler]

Is it possible that the IP address is coming across an Uplink port, and the switch is swapping the MAC address for forwarding purposes?

[Christoph]

Probably it is not a loop, but a duplicate IP address.

Port state "dormant" means the port is part of a logical link, e.g. a link aggregation.