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phil2982
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Two bridges with the same MAC address

Mon Mar 27, 2023 7:23 pm

I have the CRS504 (4 port 100Gbps) switch in a very simple configuration almost straight out of the box with 2 bridges:

“Mgmt”: contains just the mgmt port.
”bridge”: contains all the qsfp ports.

I noticed that I have activity on 3 of my plugged-in qsfp ports but zero traffic showing on “bridge”. I then noticed that the MAC address of both bridges is the same. I did not configure it like this and i am hesitant to make any changes as it is now in production. So a few questions:

1. Is this normal/expected?
2. Why is there zero traffic on “bridge” even though three of its ports have activity?
3. Why does Torch showing nothing on the 3 ports, even though there is activity? For example, I run a ping from one device to another and I would expect to see the icmp traffic when Torching the ports.

Thanks
 
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mkx
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Re: Two bridges with the same MAC address

Mon Mar 27, 2023 7:34 pm

Having same MAC on different bridges is awkward but doesn't necessarily break anything ... as long as they don't become part of same L2 network.

Bridge has different personalities (read more in this article). MAC address is only used by "the switch-facing interface of the router", "bridge activity" is also about same entity.

Torch will only see trafic between two switched ports if it's not HW offloaded. Your switch is a very good one and can offload (almost) everything to switch chip (it's the only way to consistently reach wire-speed transfers), so it's normal you don't see traffic. If you have to sniff traffic, first disable HW offload on port you want to check.
 
phil2982
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Re: Two bridges with the same MAC address

Mon Mar 27, 2023 10:48 pm

Thank you for the reply.

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