Switch MAC Address

Answered Question
Jan 2nd, 2008

Hi, Can anyone please help...I am trying to find out the MAC address that a 3560G would use for DHCP requests as it turns out it is not the base mac address you get from a show ver....


Is there a command to see the mac address(es) associated with a 3560G?


Much apprecieated


Urfan

Correct Answer by Jon Marshall about 9 years 1 month ago

Hi Urfan


Apologies if i am still not understanding but the following command "sh int | include line protocol | Hardware" (note NOT "sh int | include line | EtherSVI) gives the following


SW1#sh int | include line protocol | Hardware

Vlan1 is up, line protocol is up

Hardware is EtherSVI, address is 0019.060d.1c40 (bia 0019.060d.1c40)

FastEthernet0/1 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c03 (bia 0019.060d.1c03)

FastEthernet0/2 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c04 (bia 0019.060d.1c04)

FastEthernet0/3 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c05 (bia 0019.060d.1c05)

FastEthernet0/4 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c06 (bia 0019.060d.1c06)

FastEthernet0/5 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c07 (bia 0019.060d.1c07)

FastEthernet0/6 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c08 (bia 0019.060d.1c08)

FastEthernet0/7 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c09 (bia 0019.060d.1c09)

FastEthernet0/8 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0a (bia 0019.060d.1c0a)

FastEthernet0/9 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0b (bia 0019.060d.1c0b)

FastEthernet0/10 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c0c (bia 0019.060d.1c0c)

FastEthernet0/11 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c0d (bia 0019.060d.1c0d)

FastEthernet0/12 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0e (bia 0019.060d.1c0e)

FastEthernet0/13 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0f (bia 0019.060d.1c0f)

FastEthernet0/14 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c10 (bia 0019.060d.1c10)

FastEthernet0/15 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c11 (bia 0019.060d.1c11)

FastEthernet0/16 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c12 (bia 0019.060d.1c12)

FastEthernet0/17 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c13 (bia 0019.060d.1c13)

FastEthernet0/18 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c14 (bia 0019.060d.1c14)

FastEthernet0/19 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c15 (bia 0019.060d.1c15)

FastEthernet0/20 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c16 (bia 0019.060d.1c16)

FastEthernet0/21 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c17 (bia 0019.060d.1c17)

FastEthernet0/22 is administratively down, line protocol is down (disabled)

Hardware is Fast Ethernet, address is 0019.060d.1c18 (bia 0019.060d.1c18)

FastEthernet0/23 is administratively down, line protocol is down (disabled)

Hardware is Fast Ethernet, address is 0019.060d.1c19 (bia 0019.060d.1c19)

FastEthernet0/24 is administratively down, line protocol is down (disabled)

Hardware is Fast Ethernet, address is 0019.060d.1c1a (bia 0019.060d.1c1a)

GigabitEthernet0/1 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 0019.060d.1c01 (bia 0019.060d.1c01)

GigabitEthernet0/2 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 0019.060d.1c02 (bia 0019.060d.1c02)


Jon

Correct Answer by Jon Marshall about 9 years 1 month ago

Urfan


Are you talking about the switch itself getting an IP address to use ?.


If so it should be the vlan interface that you are using for management of the switch - vlan 1 by default unless you have changed it.


Jon

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Jon Marshall Wed, 01/02/2008 - 06:28

Urfan


Do you mean the switch forwarding on DHCP requests with the "ip helper-address" command.


If so the mac-address will be the one that is on the L3 interface connected to DHCP server vlan.


Or did you mean something different.


Jon

farkascsgy Wed, 01/02/2008 - 06:40

Hello,


show interface vlan 10 shows the MAC address of your VLAN10 interface, also you can check the connected devices' (like PC) MAC addreses with show mac-address-table command.


bye

FCS


Please rate me if I helped.

Urfan Khaliq Wed, 01/02/2008 - 06:42

mmm Im not sure....What im trying to find out is the mac address that the switch will use to request an IP address in order for the DHCP based auto configuration and the DHCP Client Request Process...


We have a DHCP server which is based on mac addresses and hands out IP addresses pre assigned to every MAC address...it is for this that I need the MAC address that the switch will request an IP against..


http://www.cisco.com/en/US/products/hw/switches/ps5528/products_configuration_guide_chapter09186a0080878d41.html



Urfan

Correct Answer
Jon Marshall Wed, 01/02/2008 - 06:50

Urfan


Are you talking about the switch itself getting an IP address to use ?.


If so it should be the vlan interface that you are using for management of the switch - vlan 1 by default unless you have changed it.


Jon

Urfan Khaliq Wed, 01/02/2008 - 06:54

Aah yes your Right. Thanks Jon...so am I right in thinking that the only way to find out that mac address is sho int vlan 1? is there a command that will give me all the mac addresses that the switch has?


Urfan

farkascsgy Wed, 01/02/2008 - 07:11

If you issue the show mac-address-table command you will see


Vlan Mac Address Type Ports

---- ----------- -------- -----

All 00xx.xxxx.xxxx STATIC CPU

All 00xx.xxxx.xxxx STATIC CPU

All 00xx.xxxx.xxxx STATIC CPU

All 00xx.xxxx.xxxx STATIC CPU


These belongs to the switch itself and not to the connected devices.


For DHCP concern you need to see the management vlan's address in the DHCP server's log. Not a good idea to use VLAN1 as management VLAN.


bye

FCS


PLease rate me if I helped.


Urfan Khaliq Wed, 01/02/2008 - 07:32

Hi Thanks for that but thats not quite what I am looking for...I am after a complete list of MAC addresses associated with a switch....so at the very least that would be one for each port and the vlans etc?


Urfan

farkascsgy Wed, 01/02/2008 - 07:45

Sir,


show mac-address-table command shows the CAM atble of the switch which contains all MAC addresses which is connected to the switch, including the local VLAN interfaces.

Please check it on a device.


bye

FCS


Please rate me if I helped.

Urfan Khaliq Wed, 01/02/2008 - 08:04

Hi,


Im afraid you are mistaken or you are not understanding the question...I am wanting the complete list of Mac addresses available to the switch so taht would be one for each port I would imagine at the least? I have done the show mac-address-table command and output is attached. As you can see it is not what I am after...


Urfan



farkascsgy Wed, 01/02/2008 - 08:12

Was there any connected device when you issued the show mac-address-table command?

show ip interface brief shows the port status (should be up up)


I am sure that your friend is the show mac-address-command


http://www.cisco.com/univercd/cc/td/doc/product/lan/cat4000/12_18a/command/show1.htm#1024439


http://articles.techrepublic.com.com/5100-1035_11-6125413.html


bye

FCS

Please rate me if I helped.


Urfan Khaliq Wed, 01/02/2008 - 08:18

hi nothing is connected to the switch and as I am just connectd via a console cable.


I am stuck with this as this is really bugging me! I thought there was a command which would give me all the mac addresses that the switch uses (not the mac addresses of devices connected to the switch)


Urfan


farkascsgy Wed, 01/02/2008 - 08:21

Urfan,


From the output you can see the STATIC and CPU label, these MACs belong to the switch the DYNAMIC ones are learned from the connetced devices, you can also add static mac addresses to the swithcport if you want.


bye

FCS


Please rate me if I helped.

Urfan Khaliq Wed, 01/02/2008 - 08:24

Then how is it that the base mac address is not in the list neither is the vlan1 mac address?


Urfan

Urfan Khaliq Wed, 01/02/2008 - 09:10

Hi,


according to the page all interfaces can use the same mac address but I do not think that this is the case as you can see from the attached file...vlan1 and vlan2 (which i created as a test) both have different mac addresses....


Urfan



Attachment: 
Urfan Khaliq Thu, 01/03/2008 - 00:50

So as im using the 3560 which has unique mac addresses per vlan and interface etc then is there a command for me to see the list of mac addresses that belong to the switch? (Which is my original question)


Urfan

Jon Marshall Thu, 01/03/2008 - 01:05

Hi Urfan


Try this


switch# sh int | include line protocol | Hardware


Jon

Urfan Khaliq Thu, 01/03/2008 - 01:44

Hi Jon,


Thanks for that but its not quite what I was looking for...I am after a complete list of all MAC addresses for the switch...(and not connected devices)...I attach the output I recieve from sh interfaces | include line | EtherSVI


Many Thanks




Attachment: 
Correct Answer
Jon Marshall Thu, 01/03/2008 - 01:52

Hi Urfan


Apologies if i am still not understanding but the following command "sh int | include line protocol | Hardware" (note NOT "sh int | include line | EtherSVI) gives the following


SW1#sh int | include line protocol | Hardware

Vlan1 is up, line protocol is up

Hardware is EtherSVI, address is 0019.060d.1c40 (bia 0019.060d.1c40)

FastEthernet0/1 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c03 (bia 0019.060d.1c03)

FastEthernet0/2 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c04 (bia 0019.060d.1c04)

FastEthernet0/3 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c05 (bia 0019.060d.1c05)

FastEthernet0/4 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c06 (bia 0019.060d.1c06)

FastEthernet0/5 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c07 (bia 0019.060d.1c07)

FastEthernet0/6 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c08 (bia 0019.060d.1c08)

FastEthernet0/7 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c09 (bia 0019.060d.1c09)

FastEthernet0/8 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0a (bia 0019.060d.1c0a)

FastEthernet0/9 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0b (bia 0019.060d.1c0b)

FastEthernet0/10 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c0c (bia 0019.060d.1c0c)

FastEthernet0/11 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c0d (bia 0019.060d.1c0d)

FastEthernet0/12 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0e (bia 0019.060d.1c0e)

FastEthernet0/13 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c0f (bia 0019.060d.1c0f)

FastEthernet0/14 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c10 (bia 0019.060d.1c10)

FastEthernet0/15 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c11 (bia 0019.060d.1c11)

FastEthernet0/16 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c12 (bia 0019.060d.1c12)

FastEthernet0/17 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c13 (bia 0019.060d.1c13)

FastEthernet0/18 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c14 (bia 0019.060d.1c14)

FastEthernet0/19 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c15 (bia 0019.060d.1c15)

FastEthernet0/20 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0019.060d.1c16 (bia 0019.060d.1c16)

FastEthernet0/21 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0019.060d.1c17 (bia 0019.060d.1c17)

FastEthernet0/22 is administratively down, line protocol is down (disabled)

Hardware is Fast Ethernet, address is 0019.060d.1c18 (bia 0019.060d.1c18)

FastEthernet0/23 is administratively down, line protocol is down (disabled)

Hardware is Fast Ethernet, address is 0019.060d.1c19 (bia 0019.060d.1c19)

FastEthernet0/24 is administratively down, line protocol is down (disabled)

Hardware is Fast Ethernet, address is 0019.060d.1c1a (bia 0019.060d.1c1a)

GigabitEthernet0/1 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 0019.060d.1c01 (bia 0019.060d.1c01)

GigabitEthernet0/2 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 0019.060d.1c02 (bia 0019.060d.1c02)


Jon

farkascsgy Thu, 01/03/2008 - 01:05

Not a nice solution, but works :)

sh interfaces | include line | EtherSVI


if your vlan number is 1 and the Base MAC address is 00:12:00:90:8B:00, then the VLAN1 MAC address is 00:12:00:90:8B:01, VLAN2 00:12:00:90:8B:02


bye

FCS


Please rate me if I helped.

Urfan Khaliq Thu, 01/03/2008 - 01:49

Again I think you are mistaken as you can see from the output...my base mac address is 00:1E:49:A3:1D:00 and my vlan 1 is 001e.49a3.1d40 which is clearly not just one up from the base...


(see show ver and show int vlan 1 attached..) :-)


Many thanks


Urfan



Urfan Khaliq Thu, 01/03/2008 - 02:07

Again I think you are mistaken as you can see from the output...my base mac address is 00:1E:49:A3:1D:00 and my vlan 1 is 001e.49a3.1d40 which is clearly not just one up from the base...


(see show ver and show int vlan 1 attached..) :-)


Many thanks


Urfan

farkascsgy Thu, 01/03/2008 - 02:24

Sir,


If you correctly checked the site, what I sent http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801c9b4e.shtml#fixed


you saw that there is a show command which shows all interfaces' MAC. I thought you need only the SVI's MAC.


2950#show interfaces | include line | address

Output is similar than

2950#show interfaces | include line | Hardware


bye

FCS


Urfan Khaliq Thu, 01/03/2008 - 02:32

Again I think you are mistaken as you can see from the output...my base mac address is 00:1E:49:A3:1D:00 and my vlan 1 is 001e.49a3.1d40 which is clearly not just one up from the base...


(see show ver and show int vlan 1 attached..) :-)


Many thanks


Urfan

farkascsgy Thu, 01/03/2008 - 04:16

Urfan,


You are right with the base mac and vlan mac relation issue (I've just made a quick check on one of my device).

But the command what is on the sent link works.


bye

FCS


Please rate me if I helped.

Oliver Gorwits Tue, 03/04/2008 - 07:48

Hi Urfan,


I had the same question as you. Here is what I found out, for reference:


The CPU on a 3560 or 3750 has a stash of 64 MAC addresses allocated when the device is built, for SVI (vlan interfaces). It also has another 64 addresses for the physical ports.


You can get the "base" MAC address by doing a show version. The first 64 addresses from that address are used for physical ports. The next 64 from that address are used for SVI (vlan) interfaces.


The CPU allocates MAC addresses to vlan interfaces in the order which the interfaces are created, so they can change after a reboot of the switch. If you use more than 64 vlan interfaces, the rest all get the same MAC address as the 64th interface.


For example:


base address: xx:xx:xx:xx:3e:00

first vlan address: xx:xx:xx:xx:3e:40 (this is base + 64)

last vlan address: xx:xx:xx:xx:3e:7f (this is base + 127)


So in answer to your question, the MAC address used for DHCP will depend on the interface used, but is probably no more than 127 higher than the base address. Also, the commands posted in this thread to show the MAC addresses only show those currently in use, and not those available in the future. I don't know whether there are even more MAC addresses allocated to the switch for other purposes, sorry.


You might also find the following page interesting:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801c9b4e.shtml

[Supported Platforms for Unique MAC Address Configuration on VLAN or L3 Interfaces for Catalyst Switches]


I hope all this helps, and helps other people!


regards,

oliver.

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