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New Member

Unique MAC for each VLAN

I need to assign unique MAC to VLANs. I believe they moved mac-adress cmd, but don't seem to find it someone help me please. I have Cat4507 with IOS.

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Accepted Solutions
Cisco Employee

Re: Unique MAC for each VLAN

Unfortunately, there is no way around this on the 4500 switches. If you configure the interface as an L3 port, it will still use the same MAC address.

Here's an output from my lab switch:

C4510-A#show ip arp

Protocol Address Age (min) Hardware Addr Type Interface

Internet 10.1.1.1 - 000e.d798.57bf ARPA Vlan1

Internet 10.6.1.1 - 000e.d798.57bf ARPA FastEthernet3/1

Internet 20.2.1.1 - 000e.d798.57bf ARPA GigabitEthernet1/1

The 6500 with a Sup720 does have the ability to change the MAC address, but this feature is not available on the 4500. Having the same MAC for two IPs should be fine as long as they are not in the same VLAN, but some brain dead switches (such as Marconi), don't like seeing the same mac-address even it different vlans.

HTH,

Bobby

*Please rate helpful posts.

8 REPLIES
New Member

Re: Unique MAC for each VLAN

Anybody???

Hall of Fame Super Silver

Re: Unique MAC for each VLAN

It appears you are out of luck on this platform. See http://www.cisco.com/en/US/partner/products/hw/switches/ps700/products_tech_note09186a00801c9b4e.shtml

Specifically, that doc states:

Catalyst 4500/4000 Supervisor Engine III/IV

The Catalyst 4500/4000 Supervisor Engine III/IV does not currently support a change of MAC address. The MAC address on the interface is the default BIA, which is the same for all interfaces.

The mac-address command is unrecognized for the Catalyst 4500/4000 with Supervisor Engine III/IV.

cat4kIOS(config)# interface vlan 110

cat4kIOS(config-if)# mac-address ?

% Unrecognized command

cat4kIOS(config-if)# mac-address

Hope this helps. Please rate helpful posts.

Cisco Employee

Re: Unique MAC for each VLAN

Hi Prerak,

All Routed ports on the Catalyst 4500 Series get the same MAC address (inside we differentiate the SVI by VLAN id). This address is chosen from chassis IDPROM

Additionally, we do not support a change of MAC address on this platform.

http://www.cisco.com/en/US/partner/products/hw/switches/ps700/products_tech_note09186a00801c9b4e.shtml#cat4ksup

This applies to the SupIII,IV, and V.

HTH,

Bobby

*Please rate helpful posts.

New Member

Re: Unique MAC for each VLAN

I am confused, I got following response from Cisco Customer Support. I put in commands but doesn't seem to be working:

mac-address-table static "mac-addr" {vlan vlan-id} {interface type}

for example:

Switch(config)# mac-address-table static 0050.3e8d.6400 vlan 100 interface fastethernet5/7

Here?s the link that contains more information on that:

http://www.cisco.com/en/US/products/hw/switches/ps4324/products_command_reference_chapter09186a00803ff0d0.html#wp1977013

Let me know if this helps,

New Member

Re: Unique MAC for each VLAN

What's my work-around? I read some where about per-valn mac table, I do I configure that?

Cisco Employee

Re: Unique MAC for each VLAN

Hi Prerak,

That does not change the MAC address of the interface. That command simply creates a static entry which tells the switch that any time it receives a frame in Vlan100 with a destination MAC address of 0050.3e8d.6400, that the frame will be sent out of interface fa5/7.

As to your other question:

"What's my work-around? I read some where about per-valn mac table, I do I configure that?"

There is no workaround on this platform where you can have unique MAC addresses on routed interfaces.

As for the per-vlan MAC table, this exists by default. Each entry in the MAC address table contains the following information: Vlan, mac address, type (dynamic, static, permanent), and port which the address was learned on).

So the same MAC address can exist with no problems in multiple VLANs.

HTH,

Bobby

*Please rate helpful posts.

New Member

Re: Unique MAC for each VLAN

Hi Bobby,

Is it possible to send actual interface MAC and not the VLAN mac? The problem is I have two VLANs(using two different IPs and interfaces) going to a switch.

My CAT4507 is advertising one mac for two IPs which is confusing the switch on other end.

Internet 10.18.88.220 - 0016.4777.81ff ARPA Vlan2

Internet 10.18.88.236 - 0016.4777.81ff ARPA Vlan4

Cisco Employee

Re: Unique MAC for each VLAN

Unfortunately, there is no way around this on the 4500 switches. If you configure the interface as an L3 port, it will still use the same MAC address.

Here's an output from my lab switch:

C4510-A#show ip arp

Protocol Address Age (min) Hardware Addr Type Interface

Internet 10.1.1.1 - 000e.d798.57bf ARPA Vlan1

Internet 10.6.1.1 - 000e.d798.57bf ARPA FastEthernet3/1

Internet 20.2.1.1 - 000e.d798.57bf ARPA GigabitEthernet1/1

The 6500 with a Sup720 does have the ability to change the MAC address, but this feature is not available on the 4500. Having the same MAC for two IPs should be fine as long as they are not in the same VLAN, but some brain dead switches (such as Marconi), don't like seeing the same mac-address even it different vlans.

HTH,

Bobby

*Please rate helpful posts.

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