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New Member

duplicate

Hello

Kindly;examine the attached File....

Why we have duplicate mac address ?

10xs

15 REPLIES
Hall of Fame Super Blue

Re: duplicate

Hi Ali

What is gigabit 0/1 - is it a trunk link to another switch ?

Jon

Re: duplicate

Hi

What is the configuration of this ports i mean r they trunk ports or access ports.

Thanks

Mahmood

New Member

Re: duplicate

Hello

no access Port...

10xs

Hall of Fame Super Blue

Re: duplicate

Ali

What is attached to this port ?

Jon

Silver

Re: duplicate

Hi ,

I also observed it on my 3750 switch (L3)...

different mac-address are assigned to same interface...

copy the mac-address and do the sh arp | in mac-address for g0/1. Do it for all mac-addresses ..you will get the exact IP for only one mac-address, not for all...

pl clear mac-address table and check the issue...

I observed that when there is a fluctuation or flap in network we will get this type of output.

cheers :)

satish

New Member

Re: duplicate

Hello

normal Pc attached to this Port

10xs

Re: duplicate

I seriouslt think the link in question is a trunk.

Satish, i have not seen this type of behavior on the 3750 switch. You will multiple mac-addresses on the port connecting to a router and also a SVI configured on the switch for the same subnet.

The ouput on the other hand shows mac-addresses and that too in different vlans which should be possible only when the link is a trunk

can you post output of sh int g0/1 switchport

Narayan

New Member

Re: duplicate

Hello!

Sorry this is a Trunk port...

sh int g0/1

GigabitEthernet0/1 is up, line protocol is up

Hardware is Gigabit Ethernet, address is 0002.b9b8.cd31 (bia 0002.b9b8.cd31)

Description: To xxxx

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive not set

Auto-duplex (Full), link type is autonegotiation, media type is SX

output flow-control is off, input flow-control is off

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:01, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

5 minute input rate 6961000 bits/sec, 7683 packets/sec

5 minute output rate 61000 bits/sec, 62 packets/sec

152984413 packets input, 1546610108 bytes, 0 no buffer

Received 117454707 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 74766732 multicast, 0 pause input

29242288 packets output, 381330967 bytes, 0 underruns

0 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 pause output

0 output buffer failures, 0 output buffers swapped out

NoW its become Clear,can i know the Reason and How to Solve This?

10xs

Re: duplicate

Since the trunk port is connected to another switch, it will learn all the mac-address from the downstream switch on that port.

say if you have a router connected to switchA and has a trunk connection to switchB, then switchA should know all the mac addresses for the nodes on switchB for forwarding frames that are sent from the router to these devices

HTH, rate if it does

Narayan

New Member

Re: duplicate

Narayan

is there any Problem;why only this mac relearning 3 Times ON THE Same Interface.I Think its is a unnormal Behavior.reexamine the attached File

10xs

Cisco Employee

Re: duplicate

Hi Ali,

How are you !!

Could you please try clearing the mac-address table using " clear mac-address table " command and check if still shows the same mac in different vlans on the trunk port. One of the reason for this would be if there is a user who is connecting his PC in different switchports which belongs to different vlan, then the same mac-address might be see on the different vlans

HTH,

-amit singh

New Member

Re: duplicate

amit My Freind How r You;Hope You Doing well.Say Hello Ankur i miss him so much...

Cisco Employee

Re: duplicate

Hi Ali, I am fine and doing well.. How are you doing.. I will pass on your message to Ankur. he is very busy now a days..

Did you clear the mac-address table ? Check and update us on the status.

-amit singh

New Member

Re: duplicate

Hello amit!

if so;How can i trace the Ip Address for this PC.e.g How can i know its ip address..

10xs amit

Silver

Re: duplicate

Hi Narayan ,

I've small doubt..In which situation we will get multiple mac-addresses for same port...

Cheers :)

Satish

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