switch mac address

[tahir1234]

Hi guys,

Ok , I am studying little bit of switching technology for my day to day job requirement. May be following are very basic questions for you guys but really difficult to understand for me.

• How one can fine the MAC address of a cisco switch. For example, when I run "sh ver" I get the MAC address. & when I run "sh mac addre-table"

       I also get the MAC address. So what MAC address is announced in BPDU's to decide the root of the network ?

• How to fine the port priority of a cisco switch ?

Thanks

Tahir.

[Andrew Khalil]

Dear Mousti,

Greetings,

I would like to point you that it really depends on the switch model itself but not because it's by luck or just different algorithms are working on the different IOSs for no reason as you think, the idea behind it, is the ability and capability of the model itself, for example, if your model is supporting multiple IPs to a single mac address, so no need that the switch changes the mac! isn't it.

One more example, if your switch supports per vlan mac address table, so no need to change the mac as well, as each mac address table will work separately without having an impact on the other ones! but if the switch is not supporting any of these functions, so the mac add of the SVIs will be different! 

I see it making sense! 

I wish my reply is helpful enough or added any new info. for your knowledge so that I can get your rating support! 

Thanks in advance! 

Bst Rgds,

Andrew Khalil

[moallina15]

Hey Guys..thanks for your input(s). I was not having a question, I was just expanding the answers to the original question/post. 

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Regards,

Abdul 

[kgermen]

Hi all,

I have reviewed all the responds under this title. I am a beginner who started the "introduction to network" class recently. Right now, I am studying MAC address tables in chapter 5, Ethernet on Netacad. I understand that switches only direct the frames to the correct end device or router as layer 2 devices according to their dynamic MAC addresses. There are animations that show how a switch learn MAC addresses and port numbers from incoming frames and send them to the end devices. According to the animations and the explanations in study notes in netacad, a switch doesn't make any MAC address comparison while receiving a frame. I infer from that a switch doesn't need any MAC address number, and so they cannot drop any frame.  They are just using the MAC addresses of the end devices that are connected to them in LAN to deliver the frames. 

If I am wrong, please enlighten me about this issue.

Best regards, 

Koray

[Durbaca]

Hey Koray,

This question is a bit more complex than intro chapters.

Indeed, a switch, up to your reading, does not have a MAC of itself. Its just handling and forwarding incoming frames according to the MACs in the frames it sees.

Yet - much later on - when you get to SVIs you will see that it rly participates in the discussion - therefore it needs a L2 MAC. Furthermore, in STP even later on - you get a reference "switch MAC address" which led myself to this question as well.

I hope this helps,

Keep reading on and you'll get to these answers !

Gl,

D

[ruudg]

Is there a command (or commands) that returns all the MAC addresses in use by the switch? So both the base MAC and any MAC assigned to ports/VLANs/trunks/whatever else there is. Or is it possible to calculate the range of MAC addresses that a switch can use? I.e. maybe the last 2 bytes of the MAC address can be used by the switch to generate MAC addresses?

[m_pebbeti]

You could use #show switch or in case of Nexus #show module. It will give you range of mac addresses switch uses.