Re: FreeBSD boots too fast on Dell PE850
- From: Danny Braniss <danny@xxxxxxxxxxxxx>
- Date: Fri, 18 Aug 2006 15:27:35 +0300
2006/8/18, Patrick M. Hausen <hausen@xxxxxxxx>:because there isn't?
On Fri, Aug 18, 2006 at 01:23:15PM +0200, Martin Horcicka wrote:
Unfortunately, I don't know how it works exactly. In our case when the
autodetection is disabled and there is e.g. 100/full configured
manually on both, switch and the FreeBSD box, ifconfig shows the
interface status wery early as "active". I suspect the switch (Cisco)
to activate the port (from the point of view of the FreeBSD box) but
not to forward any "normal" frames until the Spanning Tree Protocol
procedure is finished for that port. But it's just a guess. I don't
know the negotiation protocol in Ethernet at all and I would really
welcome a commentary from someone who does.
This is indeed the case.
The switch port goes up. Then the port goes into either the forwarding
or the blocking state. The transition period usually takes between 30
and 50 seconds, which may be to long for some devices.
spanning-tree portfast puts the port into the forwarding state
immediately but still participates in STP, so eventually a loop
will be detected and the port put back into blocking state again.
This is a little off-topic (and I'm no Cisco specialist) but I'm
afraid that the loop detection won't happen with portfast. Cisco.com
says (the first page that Google gave me):
---
Understanding How PortFast Works
Spanning-tree PortFast causes a port to enter the spanning-tree
forwarding state immediately, bypassing the listening and learning
states. You can use PortFast on switch ports connected to a single
workstation or server to allow those devices to connect to the network
immediately, rather than waiting for the port to transition from the
listening and learning states to the forwarding state.
Caution: PortFast should be used only when connecting a single end
station to a switch port. If you enable PortFast on a port connected
to another networking device, such as a switch, you can create network
loops.
When the switch powers up, or when a device is connected to a port,
the port normally enters the spanning-tree listening state. When the
forward delay timer expires, the port enters the learning state. When
the forward delay timer expires a second time, the port is
transitioned to the forwarding or blocking state.
When you enable PortFast on a port, the port is immediately and
permanently transitioned to the spanning-tree forwarding state.
---
But then I don't see any difference between using portfast and
disabling Spanning Tree Protocol frames for that port at all. :-/
if you are connecting a host to a switch, you can safely drop Spanning tree.
from experience, even with SP enabled, the loop is detected, but not always
the correct port is disabled :-(.
danny
Martin
The layer 2 interface is, of course, "up" during all this
mumble - otherwise the switch could not send & receive STP frames.
This is what confuses hosts waiting for DHCP or similar.
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