The only thing that comes to my mind is that you could have the same address if you have port-channel configured and these ports are the part of such port-channel. But I suppose that the bia (Burned-in address) bia 0015.fa3a.3c40 should be different!
MAC addresses should be unique on each network. They can be same in different networks. i.e MAC-address /layer 2 information changes with each hop.
"Every interface of router have same MAC"
This is right behaviour as each interface of the router will be connected to different network. So it will be highly unlikely that mac-addresss clash would take place.
In case of switch "It shows different MAC for every port"
This is also correct as switches can be used as Layer 3 and as well as in a layer 2 environment. Chances are mac-addresses might clash within same network. Consider cases like SVI/VLAN interfaces, routed interfcaes or plain layer interfaces. So it required unique mac on each interface.
Let me explain how this works.... Each switchport interface does have a Mac address. If you do a show version you'll see the Mac address and the (bia- burned in address). So when you do a sh ip int and see the Mac you will notice that all the switch does is increment each switchport by the following number or letter. Remember switches use hexadecimal so after 0-9 you have A-F. Your example actually showed you that.
GigabitEthernet0/1 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 0022.0ca8.1481 (bia 0022.0ca8.1481) <----- 1481 thru 0-9 then 148A thru F.
GigabitEthernet0/2 is down, line protocol is down (notconnect)
Hardware is Gigabit Ethernet, address is 0022.0ca8.1482 (bia 0022.0ca8.1482)
GigabitEthernet0/3 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 0022.0ca8.1483 (bia 0022.0ca8.1483)
GigabitEthernet0/4 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 0022.0ca8.1484 (bia 0022.0ca8.1484)
It shows different MAC for every port. Please help !!!!
Hopefully this clarifies your issue and now you understand how it works. Also, study hexadecimal and you'll really be able to read a packet and understand what's going on. it helped me exponentially.
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