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.
I also get the MAC address. So what MAC address is announced in BPDU's to decide the root of the network ?
BPDU's are used Spanning-tree, and while there is more to be explained than that, the easiest way is to point you to the section of cisco's site that covers the configuration, explanation of and adminitration of spanning-tree, and its uses.
I hope this helps, if you need anything else just post any additional questions.
Thanks Norman for your reply.
The document you refered is much technicial. I only need the answer of one question.
Your switch is likely to have many MAC addresses.
If you do a show interface for each of the interfaces, you will probably find that each one has a different MAC address.
There is one "master" MAC address for the switch, known as the Bridge ID. You can see that be doing a show spanning-tree and looking for the "Bridge ID" (not necessarily the Root ID).
If you do a show mac-address-table, those are not the MAC addresses of your switch, but the MAC addresses of the things attached to your switch, together with the ports they are attached to.
Does that help?
Yes Kevin , it is good explaination but when we run "show version" we see the MAC address. So is this MAC address the Bridge ID that is used in spanning-tree for the selection of root bridge ?
Not all switches will tell you the base MAC address for a show version. For example, my 4500s do not, but my 3560s do so. And in my 3560s, yes, the MAC address shown in show version is the same as the Bridge ID shown in show spanning-tree.
But the really reliable way to find out the Bridge ID used in spanning-tree is to do a show spanning-tree.
[Kevin Dorrell] If you do a
, those are not the MAC addresses of your switch, but the MAC addresses of the things attached to your switch, together with the ports they are attached to.
i agree though if you type show mac-address-table | i No then I think you'll find what you're after.
The mac address of a switch is usually the preceding number of the MAC-Address on the first port .
Eg: The mac-address on the first port gi0/1 is 0019.e728.8101. The mac address of the switch would be 0019.e728.8100.
I know this is old but I recently learned this command. Try it out. It shows the mac address of the interface, not what's attached.
show interfaces | i (.* line protocol is )|(.* address is)