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Mac-Address lost

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bman68
Occasional Advisor

Mac-Address lost

I have a client device connected to 5406zl and after the port transitions from up>down>up again the Mac-Address goes missing. If I perform a "sh mac-address " I see a valid mac until after this transition.. I am using bdpu-filter on the port but that is it..
8 REPLIES
Mohammed Faiz
Honored Contributor

Re: Mac-Address lost

Hi,

What type of interface is it and what firmware revision are you running on your 5406?
bman68
Occasional Advisor

Re: Mac-Address lost

J8697A Configuration Editor; Created on release #K.14.41. The interface is connected to a thin client (HP) using a Broadcom Netlink 57xx series adapter. I realize we are behind on our release so we will update that this evening. I have forced 10/100 and am using bdpu-filter to reduce the time it takes for the port to come up (the client is diskless).
Pieter 't Hart
Honored Contributor

Re: Mac-Address lost

bpdufilter is not the option you need.
you need "portfast" to skip the listening/learning state of stp.

Richard Brodie_1
Honored Contributor
Solution

Re: Mac-Address lost

It's not surprising that the Mac address is flushed when the port goes down. It just means that the switch will (or at least should) flood packets until it relearns the address.

However, it it doesn't relearn it, it's possible that the client has stopped transmitting. If the problem is specific to the client, I'd be looking at firmware updates for that too.
bman68
Occasional Advisor

Re: Mac-Address lost

Well I thought port-fast was a Cisco command and the bdpu-filter was sort of an equiv? Since the same behavior is seen on both Cisco and HP with or without port-fast (bdpu-filter) I have to think that it is a client issue and maybe related to the broadcom NIC in the device. Maybe non-standard signals or something I don't know..
Pieter 't Hart
Honored Contributor

Re: Mac-Address lost

portfast and bpdufilter are definitly not the same.
You are right, in the 5400 CLI guide i find no reference to portfast (my history is from cisco ofcourse).

you need to configure an adminedge-port:
Syntax: [no] spanning-tree admin-edge-port
Enable admin-edge-port on ports connected to end nodes.
During spanning tree establishment, ports with adminedge-port enabled transition immediately to the
forwarding state.

What possibly happens is
- the port comes up
- the client issues a dhcp request
- but the switchport is not yet in the forwarding state
- so the packet is lost.
- the port enters the forwarding state
- but the client doesn't resend subsequent dhcp requests (this is a client issue)
- the adress flush timer on the switch expires
- and the adress is flushed.
Pieter 't Hart
Honored Contributor

Re: Mac-Address lost

With only bpdu-filter anabled, the port is operational and a spanning-tree topology change occurs, then the port remains forwarding.
But when a port comes up it will still go throug blocked, listening, learning, forwarding states.

this describes the bpdu-filter from the Adv Traf Gde:

- Ports configured with the BPDU filter mode remain active (learning and forward frames); however, spanning-tree cannot receive or transmit BPDUs on the port. The port remains in a forwarding state, permitting all broadcast traffic.

- The bpdu-filter option forces a port to always stay in the forwarding state and be excluded from standard STP operation.

bman68
Occasional Advisor

Re: Mac-Address lost

tried that.. same behavior.. A capture reveals that when the client port drops out I see a lot of ARP requests. Funny thing is it appears almost 60 seconds (wireshark time) after the port drop. I see the same thing on the server capture.. strange behavior.. Thanks very much for the information..