Controller Based WLANs

Why do I see the same mac address from two different ports on the Aruba controller on the uplink switch?

Aruba Employee

Question: Why do I see the same mac address from two different ports on the Aruba controller on the uplink switch?

 

Environment: This article applies to all the controller models and OS version

 

On Aruba controller, each port is assigned a unique mac address.
 
(Aruba-620) # show interface fastethernet 1/0
 
FE 1/0 is up, line protocol is up
Hardware is FastEthernet, address is 00:1A:1E:20:87:61 (bia 00:1A:1E:20:87:61)
Description: FE1/0 (RJ45 Connector)
Encapsulation ARPA, loopback not set
Configured: Duplex ( AUTO ), speed ( AUTO )
Negotiated: Duplex (Full), speed (100 Mbps)
MTU 1500 bytes, BW is 100 Mbit
Last clearing of "show interface" counters 0 day 3 hr 40 min 25 sec
link status last changed 0 day 3 hr 36 min 21 sec
    18993 packets input, 6003286 bytes
    Received 441 broadcasts, 0 runts, 0 giants, 0 throttles
    0 input error bytes, 0 CRC, 0 frame
    439 multicast, 18552 unicast
    16736 packets output, 2131277 bytes
    0 output errors bytes, 0 deferred
    0 collisions, 0 late collisions, 0 throttles
This port is TRUSTED
POE Status of the port is ON
 
(Aruba-620) # show interface fastethernet 1/1
 
FE 1/1 is up, line protocol is down
Hardware is FastEthernet, address is 00:1A:1E:20:87:62 (bia 00:1A:1E:20:87:62)
Description: FE1/1 (RJ45 Connector)
Encapsulation ARPA, loopback not set
Configured: Duplex ( AUTO ), speed ( AUTO )
MTU 1500 bytes, BW is 100 Mbit
Last clearing of "show interface" counters 0 day 3 hr 40 min 30 sec
link status last changed 0 day 3 hr 7 min 37 sec
    1811 packets input, 124598 bytes
    Received 1755 broadcasts, 0 runts, 0 giants, 0 throttles
    0 input error bytes, 0 CRC, 0 frame
    71 multicast, 56 unicast
    61 packets output, 22664 bytes
    0 output errors bytes, 0 deferred
    0 collisions, 0 late collisions, 0 throttles
This port is TRUSTED
POE Status of the port is OFF

 
However, all the VLANs on the controller shares the same mac address (VLAN 1’s mac address).

(Aruba-620) #show interface vlan 1
 
VLAN1 is up line protocol is down
Hardware is CPU Interface, Interface address is 00:1A:1E:20:87:60 (bia 00:1A:1E:20:87:60)
Description: 802.1Q VLAN
Internet address is 172.16.0.254  255.255.255.0
IPv6 Router Advertisements are disabled
Routing interface is enable, Forwarding mode is enable
Directed broadcast is disabled, BCMC Optimization disabled ProxyARP disabled Suppress ARP enable
Encapsulation 802, loopback not set
MTU 1500 bytes
Last clearing of "show interface" counters 0 day 3 hr 44 min 2 sec
link status last changed 0 day 3 hr 44 min 2 sec
Proxy Arp is disabled for the Interface
 
(Aruba-620) #show interface vlan 200
 
VLAN200 is up line protocol is up
Hardware is CPU Interface, Interface address is 00:1A:1E:20:87:60 (bia 00:1A:1E:20:87:60)
Description: 802.1Q VLAN
Internet address is 10.1.200.10  255.255.255.0
IPv6 Router Advertisements are disabled
Routing interface is enable, Forwarding mode is enable
Directed broadcast is disabled, BCMC Optimization disabled ProxyARP disabled Suppress ARP enable
Encapsulation 802, loopback not set
MTU 1500 bytes
Last clearing of "show interface" counters 0 day 3 hr 44 min 6 sec
link status last changed 0 day 3 hr 40 min 22 sec
Proxy Arp is disabled for the Interface
Auto Operstate up is enabled for this Interface
 
(Aruba-620) #

 
VLANs are mapped to the physical ports on the Aruba controller. At times, same VLAN can be mapped to multiple ports. For Layer-2 communication, the port will use its physical mac address. However, for any Layer-3 communication, the port will use the mac address of the VLAN mapped to it.

As a result, there could be times when the uplink switch may receive communication from two different ports on Aruba controller with the same source mac address as same VLAN may be mapped to those ports.

This is an expected behavior.

 

Version history
Revision #:
1 of 1
Last update:
‎06-30-2014 03:19 PM
 
Labels (1)
Contributors
Search Airheads
cancel
Showing results for 
Search instead for 
Did you mean: 
Is this a frequent problem?

Request an official Aruba knowledge base article to be written by our experts.