I'm having a stupid attack - VLAN MAC Offset

[dane775]

For the passport 8000:


What it it...what's it used for??...(I have a few guesses)

I can't find anything on google or in the few docs I've checked.

Anyone know about that?

 

[HungryHouse]

Where are you seeing this?

 

[dane775]

A co-worker did "show config" and saw it in the VLAN IP section.

I found this definition but it doesn't give much on why I'd want to use it:

MacOffset - The mac_offset is a optional parameter that allows you to manually change the default MAC address for a logical or physical interface. Value is an integer from 0 to 507. The default is the next available value.

 

[HungryHouse]

What code is your co-worker on?
The output of "show vlan info ip" on our syste, (3.5.9)
is the following :

================================================================================
Vlan Ip
================================================================================
VLAN IP NET BCASTADDR REASM ADVERTISE DIRECTED
ID ADDRESS MASK FORMAT MAXSIZE WHEN_DOWN BROADCAST
--------------------------------------------------------------------------------

I don't see a Mac_offset in this section.

 

[dane775]

HungryHouse,

Sorry so slow...working on a big problem here in our network.

It was actually a "show config" command and under the VLAN IP info section he saw that.

On that node I think we are running 3.7.6.0 code.

Thanks for the responses!!...Dane

 

[anthonyanderberg]

The VLAN MAC offset is used by the 8600s to ensure that each IP address has a different MAC address. The box comes with a base MAC address (its contained on the only EPROM chip in the backplane) and each virtual interface gets a MAC address offset from this base MAC by a given amount. The base MAC address is also on a little sticker on the chassis. You don't need to configure the MAC offset, the system will assign them in order as you build the configuration - but when making changes it can be handy to tweak them if you've got filters or tables that you don't want to adjust.

 

[dane775]

anthonyanderberg - You ARE the man...(or at least one of the guys...*grinz atcha*)

Thanks much for your help. I had some vague fuzzy thoughts along those lines...it's nice to hear a definitive answer.

Thanks again!!...Dane

 

[OmegaVTX]

You don't need to configure the MAC offset, the system will assign them in order as you build the configuration "

This does not seem to be the case for the 5500 series. Everytime I created a vlan and assign it an IP I was required to enter a MAC Offset value.

 

[dane775]

OmegaVTX - really?....we've got some 5510s in our network and I don't remember anyone mentioning that.

 

[anthonyanderberg]

I've setup layer 3 vlans on our 5510s, and don't remember setting the MAC offset but its been a while...

What version of code are you guys running?
Maybe that's the difference.

 

[dane775]

anthonyanderberg - I don't remember hearing about that either. It may be a code difference.

Ours look like this:

Ethernet Routing Switch 5510-48T
HW:05 FW:4.2.0.11 SW:v4.2.0.002

I thought we has some 5520s but I haven't located them yet...(mucho busy today)

 

[HungryHouse]

Aha..yes, its all coming back to me now. LOL.
Yes, I did have to set MAC offsets on 5510/5520s. The documentation indicated that the system will assign one for you, but I have yet to see that becorrect. I have to assign them each time...I just utilized the same # as that of the VLAN ID. If you try to leave it blank, it will not accept the IP assignment.

I am running version V 4.2.1.004.

The reason why this was unfamiliar to me for the PP8600 is I have run versions of 3.2.x, 3.3.x, and 3.5.x code and there is no MAC offset yet (I assume that this was 3.7.x code that the rest of y'all are on).

Happy configurations all!