[Bridge] Invalid BPDU transmission?

Srinivas M.A. srinivas.aji at gmail.com
Tue Oct 5 05:40:32 PDT 2010


Both CONFIG and TCN BPDUs are used only in STP compatibility mode. In
RSTP mode, the BPDUs sent in both directions are RSTP BPDUs. So they
can be sent on the root port.

For a description of how topology changes are handled, see the section
titled "New Topology Change Mechanisms" in
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml

Is this causing any particular issue?

On Tue, Oct 5, 2010 at 3:24 PM, Rodolfo Giometti <giometti at enneenne.com> wrote:
> Hello,
>
> in function STP_transmit_check_conditions (rstplib/transmit.c) the
> case:
>
>    case IDLE:
>      if (!port->helloWhen) return STP_hop_2_state (this,
>      TRANSMIT_PERIODIC);
>      if (!port->sendRSTP && port->newInfo &&
>          (port->txCount < TxHoldCount) &&
>          (port->role == DesignatedPort) &&
>          port->helloWhen)
>        return STP_hop_2_state (this, TRANSMIT_CONFIG);
>      if (!port->sendRSTP && port->newInfo &&
>          (port->txCount < TxHoldCount) &&
>          (port->role == RootPort) &&
>          port->helloWhen)
>        return STP_hop_2_state (this, TRANSMIT_TCN);
>      if (port->sendRSTP && port->newInfo &&
>          (port->txCount < TxHoldCount) &&
>          ((port->role == RootPort) ||         <----
>           (port->role == DesignatedPort)))
>        return STP_hop_2_state (this, TRANSMIT_RSTP);
>      break;
>
> states that a RSTP bpdu can be transmitted even throught a RootPort
> which, IMHO, is not correct... only topology change BPDU should be
> sent over the RootPort. That's why I suggest to remove the line with
> the arrow (<----).
>
> Comments? :)
>
> Ciao,
>
> Rodolfo
>
> --
>
> GNU/Linux Solutions                  e-mail: giometti at enneenne.com
> Linux Device Driver                          giometti at linux.it
> Embedded Systems                     phone:  +39 349 2432127
> UNIX programming                     skype:  rodolfo.giometti
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