Why all SVI vlans have same mac address

Answered Question
Sep 10th, 2010
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hi all,


on 3550 switch where i have 3 SVI  as shown below


3550SMI#sh int
Vlan10 is up, line protocol is up
  Hardware is EtherSVI, address is 000d.28bc.fd80 (bia 000d.28bc.fd80)********************************
  Internet address is 192.168.10.1/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:03:35, output 00:03:35, output hang never
  Last clearing of "show interface" counters 1w4d
  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
     9404 packets input, 885933 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
     9705 packets output, 843523 bytes, 0 underruns
     0 output errors, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out
Vlan20 is up, line protocol is up
  Hardware is EtherSVI, address is 000d.28bc.fd80 (bia 000d.28bc.fd80)****************************

  Internet address is 192.168.20.1/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 1d15h, output 2w1d, output hang never
  Last clearing of "show interface" counters 1w4d
  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 packets output, 0 bytes, 0 underruns
     0 output errors, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out
Vlan30 is up, line protocol is up
  Hardware is EtherSVI, address is 000d.28bc.fd80 (bia 000d.28bc.fd80)************************************
  Internet address is 192.168.30.1/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:05, output hang never
  Last clearing of "show interface" counters 1w4d
  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
     7563 packets input, 733155 bytes, 0 no buffer

my default gateway is vlan 30 IP  192.168.30.1  and mac address of my default gateway is  (bia 000d.28bc.fd80)************************************

i know switches have static mac address assigned .Do this mac address is assigned to specfic switch port like fa0/23 etc?

Or is this mac address always reserverd for SVI ?


my question is even if we have different vlans with different IP address assigned how come all of them have same mac address?

Correct Answer by Jon Marshall about 6 years 8 months ago

Mahesh


You have actually asked the same question a while back in this forum. Perhaps you just forgot.


Have a read of this document which explains all about mac-address usage on Catalyst switches -


Catalyst mac address usage


Jon

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Correct Answer
Jon Marshall Fri, 09/10/2010 - 15:36
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Mahesh


You have actually asked the same question a while back in this forum. Perhaps you just forgot.


Have a read of this document which explains all about mac-address usage on Catalyst switches -


Catalyst mac address usage


Jon

mahesh18 Fri, 09/10/2010 - 15:54
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Hi jon,


thanks for reply.


i highly praise you sharp  memory this question i asked  2 years ago i forgot  and you still remember !!.


best regards

mahesh

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