Spanning Tree traffic
 

I put a sniffer on our network to monitor some aberrent behavior on one of
the hosts and fired it up to test prior to applying filters. Anyway, I
noticed a large amount of spanning tree traffic from our Cisco switch which
surprised me because I thought once the root switch was established, STP
only fired-up occasionally to resolve chages, etc.

My question: Is this normal, or do I need to dig deeper for some underlying
problem. (I didn't notice anything unusual in the STP traffic messages.)

Re: Spanning Tree traffic
 

Any port that is configured with normal spanning tree will send periodic
BDPU's,
May want to turn on portfast on ports connected directly to servers/clients.


"S. Gione" <sgione@hotmail.com> wrote in message
news:Ys17d.1066$z04.60@twister.socal.rr.com...
> I put a sniffer on our network to monitor some aberrent behavior on one of
> the hosts and fired it up to test prior to applying filters. Anyway, I
> noticed a large amount of spanning tree traffic from our Cisco switch
which
> surprised me because I thought once the root switch was established, STP
> only fired-up occasionally to resolve chages, etc.
>
> My question: Is this normal, or do I need to dig deeper for some
underlying
> problem. (I didn't notice anything unusual in the STP traffic messages.)
>
>

Re: Spanning Tree traffic
 

Hello, MC!
You wrote on Thu, 30 Sep 2004 22:15:35 -0400:

M> Any port that is configured with normal spanning tree will send
M> periodic BDPU's,
M> May want to turn on portfast on ports connected directly to
M> servers/clients.

I don't think portfast will stop BPDU's.

With best regards,
Andrey.

Re: Spanning Tree traffic
 

In article <cjifjh$2ne$1@news.aha.ru>, andyvt@email.com says...
> Hello, MC!
> You wrote on Thu, 30 Sep 2004 22:15:35 -0400:
>
> M> Any port that is configured with normal spanning tree will send
> M> periodic BDPU's,
> M> May want to turn on portfast on ports connected directly to
> M> servers/clients.
>
> I don't think portfast will stop BPDU's.
>

I agree, BPDU's are still transmited and received with or without
portfast.

--
-Ivan.

*** Use Rot13 to see my eMail address ***

Re: Spanning Tree traffic
 

Spanning tree Bridged Protocol Data Units (BPDU) are sent out every
port every 2 seconds. This rate is controlled by the SPT hello timer.

Re: Spanning Tree traffic
 

This 2-second rate is what was measured.

It seemed awfully "chatty", but if this is normal, I guess I won't worry
about it. The packets are small and represent a very low percentage of
total traffic.

Thanks.

"mh" <merv.hrabi@rogers.com> wrote in message
news:e092fc23.0410010344.10b31bbc@posting.google.c om...
> Spanning tree Bridged Protocol Data Units (BPDU) are sent out every
> port every 2 seconds. This rate is controlled by the SPT hello timer.

Re: Spanning Tree traffic
 

if you have a single switch, then you can disable spanning tree.

Let me be more specific this does not mean you can only have a single
switch in your entrie network; it means that froma routed port, if you
only have a single switch then youy can safetly disable spanning tree.
If you have two or more switches connected togther then disabling
spanning tree is generally not a good idea...

Re: Spanning Tree traffic
 

Hello, mh!
You wrote on 2 Oct 2004 14:31:30 -0700:

m> if you have a single switch, then you can disable spanning tree.

m> Let me be more specific this does not mean you can only have a
m> single switch in your entrie network; it means that froma routed
m> port, if you only have a single switch then youy can safetly
m> disable spanning tree. If you have two or more switches connected
m> togther then disabling spanning tree is generally not a good
m> idea...

It's not a good idea even with a single switch.

With best regards,
Andrey.

Re: Spanning Tree traffic
 

mh wrote:

> if you have a single switch, then you can disable spanning tree.
>
> Let me be more specific this does not mean you can only have a single
> switch in your entrie network; it means that froma routed port, if you
> only have a single switch then youy can safetly disable spanning tree.
> If you have two or more switches connected togther then disabling
> spanning tree is generally not a good idea...

I'd disagree. Spanning tree's useful even on one switch for when some
bozo manages to introduce a loop between two ports (yes, it does happen)
somehow. Then again, you can turn spanning tree off even if you have
loads of switches - you just have to make sure you don't have redundant
links between switches, and no other loops in the network.

If you get a loop, network meltdown general results, which is why
spanning tree can be a good thing. If you're not running redundant
links, and are pretty sure you won't be in the situation of someone
accidentally looping something, it's fairly safe to turn off.

It really is horses for courses - risk vs benefits - and every network
is different wrt that.

--


Velvet

Re: Spanning Tree traffic
 

On 02.10.2004 23:39 Andrey Tarasov wrote:

> Hello, mh!
> You wrote on 2 Oct 2004 14:31:30 -0700:
>
> m> if you have a single switch, then you can disable spanning tree.
>
> m> Let me be more specific this does not mean you can only have a
> m> single switch in your entrie network; it means that froma routed
> m> port, if you only have a single switch then youy can safetly
> m> disable spanning tree. If you have two or more switches connected
> m> togther then disabling spanning tree is generally not a good
> m> idea...
>
> It's not a good idea even with a single switch.
>

It is ... you most likely don't need it. Hence turn it off but don't
forget to have still BPDU guard turned on.



Arnold
--
Arnold Nipper, AN45