Link down due to STP

Jun 18, 2008 6 Replies

Hi,



I have a basic question. When STP is putting a port in Blocking mode is the physical connection to the port down as well?



I had the problem that on one port the link to a server was down right after the port was in STP blocking state.



Maybe one could give me an explaination on this.



Thanks...Andy


No. The port has to stay up to keep receiving STP BPDUs even though it doesn't forward any traffic.

Dunno - sorry.

Sam

"Sam Wilson" schrieb im Newsbeitrag news: snipped-for-privacy@scotsman.ed.ac.uk...

So a host on the port should not notice it at all, right?

Err... no, but why would a switch block a port that a host was attached to?

Sam

  1. because someone turned on bridging in the host, and spanning tree is doing exactly what it should as this is a loop bridging in windows XP sometimes gives this kind of hassle, but shouldnt be on a server....
  2. the host has the same MAC address on all ports and the switch got confused and put 1 port in err-disable (used to be common on a Sun box)
  3. 1 of the wierd mix ups that sometimes happen with link aggregation

- not setting it up on both ends, or mixing 802.1ad with cisco port aggregation....

any more?

slightly related - latest one i seem to get is Ethernet WAN links that reflect packets when there is an error (or when the transmission engineers are testing - they insist on looping circuits).

cisco routers dont seem to mind too much, but a Catalyst will err disable the port very quickly - and they dont auto recover by default....

I was really fishing to try to get the original poster to bring out that kind of issue.

I've never come across that as an issue causing err-disable. What circumstances does it happen in?

Anyway I was assuming (and looking back the assumption may have been wrong) that when the OP talked about STP blocking he was seeing his switch reporting a port in BLK mode. Reading back he may have been inferring (wrongly) that because a port was down it might be due to STP.

GigE negotiation mismatch.

Not seen that one (yet...). We have all our boxes set to recover from err-disable automatically - so much better than leaving the port down.

Sam

claimed in an error report from hosting - something about turning off all the auto Pagp style stuff and plugging several ports into the same VLAN.

So do i now - but i wasnt expecting this as Ethernet WAN behaviour....

Had this on Marconi / Ericsson SDH muxes - looping the port is part of the diagnostics & commissioning routine.

Also got it from a misbehaving BT Redcare RS-1000-D (100 Mbps on a CCTV circuit).

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