Hi Rin,
I tested on 7600 and 6500 in my lab. Here are the findings:
1. by default, all of the interfaces are layer 3 interface, since
they're configured as "no ip address". All of the MAC-address are the
same for layer 3 interfaces, as per design.
2. I changed the interface to switchport, then I found the interface
mac-address is changed to unique layer 2 mac address, which comes from
the module range(sh mod).
Both 7600 and 6500 behave the same.
By default,
7604#sh int g2/1
GigabitEthernet2/1 is administratively down, line protocol is down
(disabled)
Hardware is c7600 1Gb 802.3, address is 0013.5f1e.fe40 (bia
0013.5f1e.fe40)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s
input flow-control is off, output flow-control is off
Clock mode is auto
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output never, output hang never
Last clearing of "show interface" counters 1w0d
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
7604#sh run int g2/1
Building configuration...
Current configuration : 61 bytes
!
interface GigabitEthernet2/1
no ip address
shutdown
end
After configuring it to be a switchport,
7604#conf t
Enter configuration commands, one per line. End with CNTL/Z.
7604(config)#int g2/1
7604(config-if)#switchport
7604(config-if)#end
7604#sh int g2/
*Apr 10 21:07:30.500: %SYS-5-CONFIG_I: Configured from console by console1
GigabitEthernet2/1 is administratively down, line protocol is down
(disabled)
Hardware is c7600 1Gb 802.3, address is 001c.584c.5bf4 (bia
001c.584c.5bf4)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s
input flow-control is off, output flow-control is off
Clock mode is auto
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output never, output hang never
Last clearing of "show interface" counters 1w0d
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
Mod MAC addresses Hw Fw Sw
Status
--- ---------------------------------- ------ ------------ ------------
-------
1 0007.0e62.12e8 to 0007.0e62.12eb 5.2 12.2(33r)SRB 12.2(33)SRC Ok
2 001c.584c.5bf4 to 001c.584c.5bf7 5.2 12.2(33r)SRB 12.2(33)SRC Ok
3 0013.60a4.9a88 to 0013.60a4.9b07 2.0 12.2(33)SRC 12.2(33)SRC Ok
The 7600 I am testing is running over 12.2(33)SRC/SRB2
3. Further more, I found the layer 3 interfaces share the same mac while
layer 2 interfaces should use unique mac is by design. And all platforms
have the same behavior.
http://www.cisco.com/warp/customer/473/catmac_41263.html#topic1
For the lower end switches, the interfaces are layer 2 interface by
default so you don't see the problem.
However for ES-20 beaware of the below bug
CSCso79720 All ES20 ports use same MAC address when configured as
switchport.
Found in 12.2(33)SRC 12.2(33)SRB02
Intergrated in 12.2(33)SRD 12.2(33)SRC02 12.2(33)SRB04
HTH
Shimol
Rin said the following on 11/12/2009 10:30 PM:
Hi group,
Can someone explain why router 7600 uses the same MAC address for all VLAN
interfaces and ES20 ports? Catalyst 3560 has different MAC address for each
VLAN interface.
Thanks,
Rin
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