It's a symptom of the problem I wrote about earlier in this thread. When a
MAC becomes active on the network, the computer isn't able to communicate for
the first 50 seconds the port detects the end-system is active. The port
begins in blocking mode, then transitions to listening, then learning.
Finally, once STP determines that a looped topology hasn't occurred, the port
is set to forwarding mode. This creates havoc with any end-system that
expects to receive over-the-network information within the first 50 seconds.
IP, IPX, AppleTalk - all face the same issue.
The simple solution isn't to kill Spanning Tree on all switches - that's the
"I don't understand the problem so I'll do whatever works and create a bigger
problem" solution. The real solution is to enable portfast on all switch
ports that have end-systems directly connected. The caveat to this is to
ensure none of the end-systems are capable as acting as a bridge, forwarding
packets between LAN segments. Enabling portfast essentially disables
Spanning
Tree on a port - and Spanning Tree is used to ensure a loop-free environment.
-- Leigh Anne
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: April 30, 2001 7:15 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Spanning Tree Protocol [7:2564]
>
>
> Oh, speaking of AppleTalk. We've got a customer (not mine, but one of the
> engineers working the account bounced this off me): They claim their new
> Macs can't access the network if Spanning Tree is enabled. Supposedly this
> has been verified by Apple and TAC (but we've never had a customer lie to
> us, so that must be gospel, right. Heh, not). I don't know what exactly
> the details are, but basically it just doesn't function. The simple
> solution is to kill spanning-tree on all the switches, but this is at a
> number of public schools, and I can't wait to hear about a kid bringing in
> his Linksys 8 port 10/100 switch and melting their network.
>
> Anyone else hear such rumors?
>
> --
> Jason Roysdon, CCNP+Security/CCDP, MCSE, CNA, Network+, A+
> List email: [EMAIL PROTECTED]
> Homepage: http://jason.artoo.net/
>
>
>
> ""Priscilla Oppenheimer"" wrote in message
> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > At 11:08 AM 4/30/01, Phil Barker wrote:
> > >Strongly in favour,
> > >
> > >A similar problem occurs in an IPX environment.
> > >Make sure all Servers/Clients are 'portfast' and
> > >switch/switch disable 'portfast'.
> >
> > A similar problem happens with AppleTalk too. That's what we get for
> > expecting switches to replace hubs in a topology. ;-) They were designed
> as
> > bridges and to talk to other bridges. Despite switches being the
> > new-fangled thing (well, sort of new), a lot of their functionality is
> > vintage 1980s.
> >
> > Priscilla
> >
> >
> > >Regards,
> > >
> > >Phil.
> > >--- John Gotti wrote: > Hey
> > >all...we are having a problem where workstations
> > > > sporatically will not
> > > > be able to obtain an IP address from our DHCP
> > > > server. After about 4 minutes,
> > > > you can perform a manual renew from WINIPCFG and you
> > > > get your IP address.
> > > > This has baffled me for quite some time and I have
> > > > recently been told it is
> > > > our Cisco 2924 Switch to blame. The story I was told
> > > > is below. I welcome any
> > > > comments for or against this opinion. Thank you for
> > > > your time.
> > > >
> > > >
> > > > "It appears the problem is connected to the
> > > > spanning tree algorithm used
> > > > by the CISCO switches. By default, ports on the
> > > > switch block as they are
> > > > initialised; during this phase the port is in its
> > > > spanning tree algorithm
> > > > learning and listening state - it is not
> > > > forwarding. This is specifically
> > > > aimed at ports that will be used to connect to other
> > > > switches/routers in a
> > > > stack. After a default time (4 mins?) they switch to
> > > > the standard forwarding
> > > > mode and everything seems normal, the problem is
> > > > that you have missed all
> > > > the important DHCP broadcast and acknowledgment from
> > > > client to DHCP server
> > > > during this period.
> > > >
> > > > You can change this default state by changing the
> > > > PORT-FAST setting on
> > > > each port. The port is then immediately in the
> > > > FORWARDING mode as it is
> > > > initialised. By default this setting is DISABLED,
> > > > I have ENABLED all
> > > > ports except the ports doing the linking to other
> > > > switches"
> > > >
> > >_________________________________________________________________
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> > > > http://explorer.msn.com
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> >
> > ________________________
> >
> > Priscilla Oppenheimer
> > http://www.priscilla.com
> > FAQ, list archives, and subscription info:
> http://www.groupstudy.com/list/cisco.html
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