Re: alc(4) link autoselect problem

Pyun YongHyeon wrote:
> On Fri, Oct 09, 2009 at 07:29:08AM +0200, Ian FREISLICH wrote:
> > Pyun YongHyeon wrote:
> > > On Thu, Oct 08, 2009 at 12:38:45PM +0200, Ian FREISLICH wrote:
> > > > wgsw-24010# sh interfaces status ethernet g14
> > > >                                              Flow Link          Back   
Mdix
> > > > Port     Type         Duplex  Speed Neg      ctrl State       Pressure 
Mode
> > > > -------- ------------ ------  ----- -------- ---- ----------- -------- 
----
> > ---
> > > > g14      1G-Copper    Full    100   Enabled  Off  Up          Disabled 
Off 
> > > > 
> > > 
> > > Hmm, does your switch have an option to enable/disable downshifting
> > > feature? If so, how about toggling the option?
> > 
> > I'm not sure exactly what you mean.  There's no configuration options
> > that obviously match.
> > 
> 
> Modern PHYs have ability to correct several cabling problems, for
> example,
>  - pair swaps
>  - pair skews
>  - pair polarity
>  - automatic MDI/MDIX
>  - downshift to enable 10/100Mps link establishment with two
>    pairs by downgrading the link speed to 10/100Mbps during
>    auto-negotiation process when it can't establish 1000Mbps link.
>    Existing cables used to connect 10/100Mbps link partners may
>    have only two pairs. With two pairs PHYs can announce 1000Mbps
>    capability to link partner but it can't establish the link as
>    1000Mbps link requires 4 pairs.
> 
> Since F1 PHY seems to have above capability I just wanted to see
> whether disabling downshifting on link partner makes any
> difference.

Yes, if I tell the switch to negotiate but not to advertise
1000f, link negotiation works with this PHY:

wgsw-24010# sh interfaces advertise ethernet g14
Port: g14       
Type: 1G-Copper
Link state: Up
Auto negotiation: Enabled

                                  1000f  1000h  100f  100h  10f  10h
                                  -----  -----  ----  ----  ---  ---
Admin Local link Advertisement    no     no     yes   yes   yes  yes  
Oper Local link Advertisement     no     no     yes   yes   yes  yes  
Oper Remote link Advertisement    no     no     yes   yes   yes  yes  
Priority Resolution               -      -      yes   -     -    -  

alc0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=3198<VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_MCAST,WOL_MAGIC>
        ether 00:25:b3:6f:ab:9a
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active

Ian

--
Ian Freislich