Bit.Decoder wrote:
Hi,
Does routers have a single unique MAC address or does each of its interface have a unique physical address. I ask this because when the router gets bits coming in into its interfaces, it arranges them into frames and goes ahead to read the layer 2 header. So there must be a reference MAC address/addresses on the router which it uses to discriminate if the frame belongs to the router or not. Many Thanks
Kind Regards,
Bit
Great question-
The MAC address of each Ethernet interface, has its own assigned MAC address.
If we create Ethernet sub-interfaces, each sub-interface inherits the MAC address of the parent physical interface.
If we configure the MAC address, (instead of using the Burned In Address (bia)), then the Ethernet sub-interfaces, if any, will inherit those same MAC addresses.
R2#show run | section interface
interface FastEthernet0/0
ip address 10.0.0.2 255.255.255.0
interface FastEthernet0/1
no ip address
interface FastEthernet0/1.10
encapsulation dot1Q 10
ip address 23.0.0.2 255.255.255.0
interface FastEthernet0/1.20
encapsulation dot1Q 20
ip address 24.0.0.2 255.255.255.0
R2#show interface | inc Fast|bia
FastEthernet0/0 is up, line protocol is up
Hardware is Gt96k FE, address is c203.015d.0000 (bia c203.015d.0000)
FastEthernet0/1 is up, line protocol is up
Hardware is Gt96k FE, address is c203.015d.0001 (bia c203.015d.0001)
FastEthernet0/1.10 is up, line protocol is up
Hardware is Gt96k FE, address is c203.015d.0001 (bia c203.015d.0001)
FastEthernet0/1.20 is up, line protocol is up
Hardware is Gt96k FE, address is c203.015d.0001 (bia c203.015d.0001)
R2#show ip arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.0.0.2 - c203.015d.0000 ARPA FastEthernet0/0
Internet 23.0.0.2 - c203.015d.0001 ARPA FastEthernet0/1.10
Internet 24.0.0.2 - c203.015d.0001 ARPA FastEthernet0/1.20
R2#
Best wishes,
Keith