On Thu, Feb 07, 2008 at 01:56:32PM +0100, Hannes Reinecke wrote:
> The problem we're facing here is due to network routing in the
> connected switches.  When using static IP addresses the switch has
> to set-up the route from the initiator to the requested target using
> the tree-spanning algorithm.  This will take some time to setup,
> during which any connect() attempt from the initiator will fail with
> But as the in-kernel iSCSI tcp code is essentially stateless, it
> cannot differentiate between failures upon startup (where
> EHOSTUNREACH might be retried) and real failures during normal
> operations (where EHOSTUNREACH is indeed a critical failure).
> Note, this is while the network card has signalled the network is
> up, as from the POV of the card it is.
> We could circumvent this by pinging a target marked as automatic
> upon startup, but of course this will fail if no targets are
> configured ...
> So this a real bugger. And I have no idea how to solve it properly.
> That's why I'm using DHCP. There the routes are already setup as the
> DHCP reply somehow has to find its way back to the initiator ...

Fortunately, I am a spanning-tree protocol guru :-)

On the switchports that face your hosts and targets but *not* on the
switchports that face other switches, you want to enable a few
common but not-quite standard features.

1) Port-fast: enabled the port to go straight to the forwarding state 
2) BPDU-guard: immediately shutdown the port if STP BPDUs are

You need #2 with #1 because #1 allows the creation of transient loops.
#2 helps prevent that.  In Cisco speak:

interface gi0/1
 spanning-tree bpduguard enable
 spanning-tree portfast

In HP Procurve speak (need to be running recent firmware):
spanning-tree ethernet 10 bpdu-protection
spanning-tree ethernet 10 admin-edge-port (for RSTP networks)
spanning-tree ethernet 10 mode fast (for classic STP networks)

This will eliminate the thirty second waiting period for a port to
transition to forwarding.

Ross Vandegrift

"The good Christian should beware of mathematicians, and all those who
make empty prophecies. The danger already exists that the mathematicians
have made a covenant with the devil to darken the spirit and to confine
man in the bonds of Hell."
        --St. Augustine, De Genesi ad Litteram, Book II, xviii, 37

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