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InterVlan Routing

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Hi everyone,

Plz have a look to the below configuration first:

switch1#sh mac-address-table
!
Version 12.1
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname switch1
ip name-server 0.0.0.0
!
!
!
ip subnet-zero
!
!
!
!
!
!
spanning-tree extend system-id
!
interface FastEthernet0/1
switchport mode trunk
backup interface

Mac Address Table
------------------------------------------
Vlan Mac Address Type Ports
---- ----------- ---- -----
3 000C.5705.2214 DYNAMIC Fa0/4
3 000C.5401.8140 DYNAMIC Fa0/5
2 000C.4326.7045 DYNAMIC Fa0/3
2 000C.6516.6802 DYNAMIC Fa0/2
1 000C.3782.8690 DYNAMIC Fa0/1
1 000C.3782.8691 DYNAMIC Fa0/1

Total Mac Addresses for this criterion: 6
no fair-queue
!
interface FastEthernet0/2
switchport access vlan 2
backup interface
no fair-queue
!
interface FastEthernet0/3
switchport access vlan 2
backup interface
no fair-queue
!
interface FastEthernet0/4
switchport access vlan 3
backup interface
no fair-queue
!
interface FastEthernet0/5
switchport access vlan 3
backup interface
no fair-queue
!
interface FastEthernet0/6
backup interface
no fair-queue
!
interface FastEthernet0/7
backup interface
no fair-queue
!
interface FastEthernet0/8
backup interface
no fair-queue
!
interface FastEthernet0/9
backup interface
no fair-queue
!
interface FastEthernet0/10
backup interface
no fair-queue
!
interface FastEthernet0/11
backup interface
no fair-queue
!
interface FastEthernet0/12
backup interface
no fair-queue
!
vtp domain bigdomain
interface Vlan 1
no ip address
no ip route-cache
shutdown

vlan 2 name 2

vlan 3 name 3
!
ip classless
no ip http server
!
!
!
line con 0
transport input none
line aux 0
line vty 0 15
!
no scheduler allocate
end

I have configured intervlan routing by connecting switch 2950 to router by enabling subinterfaces on the router.I configured two vlans (2&3)as you can see in the above config.My question why iam getting two mac-addresses for vlan1. Fa0/1 is trunk port on the switch and it is connected to router fa0/1 by enabling subinterfaces for inter-vlan routing.Thanks in advance for your reply.Awaiting for your swift response.

6 replies

by netman1958

One of the mac addresses belongs to the router interface.

by pradeep2jr

hi,
Thanks for your reply and what about other mac address since one is for router interface.Awaiting your reply

by netman1958

Log in to the router and run the "sh interfaces" command. Then examine the hardware address for each interface.

by dumphrey

in order to let it work at layer 2? Seems to me it would have too.

by netman1958

It's been a while since I configured "router on a stick" however best I remember, subinterfaces inherit the MAC of the main interface. This is from a Cisco router I have here:

FastEthernet0 is up, line protocol is up
Hardware is PQUICC_FEC, address is 0040.9647.066b (bia 0040.9647.066b)

FastEthernet0.1 is up, line protocol is up
Hardware is PQUICC_FEC, address is 0040.9647.066b (bia 0040.9647.066b)

I'm hoping he will post the output of "sh interfaces" from his router as I'm kinda curious now.

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