From: asadovnikov (asadovnikov@comcast.net)
Date: Tue Aug 10 2004 - 10:35:02 GMT-3
Say you have a switch (3550) acting as L2 only with 5 VLANs and a router
(7200) connected to the switch over single gigabit interface to provide
inter-vlan routing (but does not do bridging), all 5 VLANs are trunked on
the port between router and switch. This is exactly when you would use
spantree portfast on the trunk on the switch side.
Best regards,
Alexei
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Tuesday, August 10, 2004 9:22 AM
To: tycampbell@comcast.net; Group Study
Subject: Re: spanning-tree portfast trunk
Ty,
I saw that also but thought that the only time it made sense to use portfast
on a trunk port was if the port were connected to a IP Phone.
So, I'm trying to find out more about this trunk option to the portfast
command and I'd like to see examples where this option should be used or
shouldn't be used.
I think the trunk option was really put in there by an evil cisco programmer
just to make ccie candidates go nuts.
----- Original Message -----
From: tycampbell@comcast.net
To: ccie2be ; Group Study
Sent: Tuesday, August 10, 2004 9:11 AM
Subject: Re: spanning-tree portfast trunk
Tim,
I haven't tried it with the trunk option on the portfast, I don't believe
it is needed.
I am leaning this way because when you configure the voice vlan on the
interface, the interface is put into the portfast state automatically,
without the "trunk" keyword. I think I could use a little more resaech into
this myself.
Could it be that when trunking, the portfast command is only applied, or
used by the voice vlan, and not the access vlan or native vlan ?
What I found on the DOC CD is very interesting
"To enable Port Fast on trunk ports, you must use the spanning-tree
portfast trunk interface configuration command. The spanning-tree portfast
command will not work on trunk ports."
I cannot find any reference to spanning-tree portfast under configuring
voice vlan guide for 3550, however I do have a reference to portfast in the
IPExpert student guide written by Scott Morris
:-)
-------------- Original message --------------
> Thanks Ty,
>
> Actually, I was asking about the trunk option in the spanning-tree
portfast
> [trunk] command.
>
> In your 2 examples, the trunk option doesn't appear after the
spanning-tree
> portfast command. Why not? Is that because the port is trunking in any
> case? If so, then why bother to ever include "trunk" in the portfast
> command?
>
> If the trunk option (of portfast command) isn't needed when an IP
Phone is
> attached to a port, when is it needed?
>
> Are there any situations where NOT having the trunk option configured
will
> cause problems? Or, conversely, are there situations where you MUST
have
> the trunk option or you'll have problems.
>
> Actually, I can't think of any reason why the portfast ! command has a
"trunk"
> option. It seems to be completely pointless and only serves to
distract
> ccie candidates from more important topics.
>
> What do you think?
>
> Tim
> ----- Original Message -----
> From:
> To: "ccie2be" ; "Group Study"
> Sent: Tuesday, August 10, 2004 8:14 AM
> Subject: Re: spanning-tree portfast trunk
>
>
> > Tim,
> >
> > When doing voice vlan, portfast is automatically configured wether
in
> trunk mode or not.
> >
> > here are 2 examples
> >
> > no trunking specified
> > int f0/1
> > switchport trunk encapsulation dot1q
> > switchport voice vlan 105
> > switchport access vlan 106
> > spanning-tree portfast
> >
> > trunking specified
> > ! int f0/2
> > switchport trunk encapsulation dot1q
> & gt; switchport voice vlan 105
> > switchport mode trunk
> > switchport trunk native vlan 106
> > spanning-tree portfast
> >
> > on the 2nd example, since you are trunking, you should use
"switchport
> trunk native vlan" in place of "switchport access vlan". The
spanning-tree
> portfast is automatically configured when you configure the voice vlan
(I
> believe)
> >
> > I hope that is what you were looking for :-)
> >
> > Ty
> >
> >
> > > Hi guys,
> > >
> > > Is the only time the "trunk" option can be used correctly on above
> command is
> > > when port is connected to an IP Phone?
> > >
> > > Also, if an IP Phone is connected to a port, and span portfast is
> configured
> > > without the trunk option, will that cause a problem or generate an
er! ror
> > > message?
> > >
> > > Thanks, Tim
> > >
> > >
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