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BCM371 - RGraham1 - 06-27-2009

I don't understand why interfaces 7, 8, 11, and 12 could not receive superior BPDUs.  Why does putting root guard on interfaces 5 and 6 alone ensure that SW1 becomes the root?  Could SW1 receive a superior BPDU from the two switches it's connected to?


Re: BCM371 - yostin - 06-29-2009

I believe in this situation the ISP already knows the other two switches connected to SW1 are not sending superior BPDU's. That being stated they need to control what they allow the customer to advertise into their network. So by putting it on 5 & 6 it stops customer switches from advertising a superior BPDU into ISP's switched network.