Multiple MAC Addresses in individual Switchport

[Batelco]

Hello Everyone,

While I was viewing the mac address table I stumbled across the following:

These are physical desktop machines with no virtual machines being hosted on them, and there are no Cisco IP phones used in the lab:

My question is:

would issuing the command "clear arp-cache" would temporarily alter the issue?

i also verified that these are not phantom MAC addresses as when i checked the show arp | i [MAC] for the duplicates below they were targeting different IP addresses that belong to desktop machines connecting to different interfaces "Other than Fa0/1"yet they still appear as if they were connected to Fa0/1

Show mac address-table

Show mac address-table | i Fa0/1

   2    0012.12e6.c92f    DYNAMIC     Fa0/1  
   2    0012.130f.84a2    DYNAMIC     Fa0/1
   2    0012.131b.5f2e    DYNAMIC     Fa0/1
   2    5065.f32d.37a9    DYNAMIC     Fa0/1
   2    5065.f333.9026    DYNAMIC     Fa0/1
   2    5065.f333.9680    DYNAMIC     Fa0/1
   2    5065.f335.0e32    DYNAMIC     Fa0/1
   2    5065.f33f.ab7e    DYNAMIC     Fa0/1
   2    5065.f33f.ace1    DYNAMIC     Fa0/1
   2    5065.f34a.a822    DYNAMIC     Fa0/1
   2    5065.f34a.a893    DYNAMIC     Fa0/1
   2    5065.f34a.a89a    DYNAMIC     Fa0/1
   2    5065.f34d.cd13    DYNAMIC     Fa0/1
   2    5065.f34d.cdfb    DYNAMIC     Fa0/1
   2    5065.f34d.ce69    DYNAMIC     Fa0/1
   2    5065.f34d.ce9b    DYNAMIC     Fa0/1

[Mark Malone · Accepted solution]

Hi
what exactly is the issue ?
what is directly connected of FA0/1 , usually that many macs would indicate its a trunk or as you said some virtual system
clearing arp cache is going to cause arp request to be regenerated until there answered and the tables populated again

[Batelco]

Dear Mark,

Thank you for your reply you reminded of the connected hub. yes there is a hub of 24 ports connected to Fa0/1. I will rate this particular issue as solved thanks for reminding.


Kind Regards,
Abdulla

[Batelco]

---

@Mark Malone wrote:
Hi
what exactly is the issue ?
what is directly connected of FA0/1 , usually that many macs would indicate its a trunk or as you said some virtual system
clearing arp cache is going to cause arp request to be regenerated until there answered and the tables populated again

---

Out of curiosity,

is there a timeout like 1 minute for generated requests of arp when issuing clear arp-cache? as I think it would be disastrous if answer was not sent.

Thanks & regards,

Abdulla

[Mark Malone]

Hi

with clearing arp cache it keeps sending gratuitous arps until it gets a response and wont clear the entry until it does

clear ip arp sends a single request

[Batelco]

---

Thanks for your reply.

funny thing cmd clear ip arp was not introduced for C3550 generation.

---

[Mark Malone]

This is just a guess but there old swithes and back then they had 2 images one for l2 SMI and one for l3 i think EMI , unlike now licenses to enable features
so if its pure l2 SMI maybe there was no need for the clear ip arp like under an L3 EMI image , one contains only L2 command etc while the EMI is full L3 set , but there that old there not in feature navigator to confirm