Link down due to STP
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Posted by Sam Wilson on June 19, 2008, 9:21 am
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> >> >
> >> >> I have a basic question. When STP is putting a port in Blocking mode is > >> >> the > >> >> physical connection to the port down as well? > >> > > >> > No. The port has to stay up to keep receiving STP BPDUs even though it > >> > doesn't forward any traffic. > >> > >> 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? >
> 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.... I was really fishing to try to get the original poster to bring out that kind of issue. > 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) 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. > 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? GigE negotiation mismatch. > 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.... 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 | |||||||||||||||||||||||||||||||
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Posted by Stephen on June 19, 2008, 3:29 pm
Please log in for more thread options >
>> wrote:
>> >> >
>> >> > >> >> >> I have a basic question. When STP is putting a port in Blocking mode is >> >> >> the >> >> >> physical connection to the port down as well? >> >> > >> >> > No. The port has to stay up to keep receiving STP BPDUs even though it >> >> > doesn't forward any traffic. >> >> >> >> 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? >>
>> 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.... >
>I was really fishing to try to get the original poster to bring out that >kind of issue. > >> 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) >
>I've never come across that as an issue causing err-disable. What >circumstances does it happen in? 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. >
>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. > >> 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? >
>GigE negotiation mismatch. > >> 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.... >
>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. 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). >
--
>Sam Regards stephen_hope@xyzworld.com - replace xyz with ntl | |||||||||||||||||||||||||||||||
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