Re: STP access port start-up delay or intialization to

Hi Ryan,

when you shut the port on the root bridge which connects to the forwarding
port and the designated brdige, you will notice, that it take 20 seconds
before the next port moves to listening state.

This is the max-age time the forwarding port wait for bpdu before sending an
event to the next port.

So, ports connecting to access devices - as indicated in the task - do not
have to wait for another ports max-age to expire. Hence, they can directly
just to learning and listening.

That's my understanding.

Mike

2009/5/9 Ryan West <rwest_at_zyedge.com>

> Mike,
>
>
>
> I tested for that scenario too:
>
>
>
> *Mar 1 00:02:08.175: set portid: VLAN0001 Fa0/19: new port id 8013
>
> *Mar 1 00:02:08.175: STP: VLAN0001 Fa0/19 -> listening
>
> *Mar 1 00:02:08.539: STP: VLAN0001 new root port Fa0/19, cost 19
>
> *Mar 1 00:02:08.539: STP: VLAN0001 sent Topology Change Notice on Fa0/19
>
> *Mar 1 00:02:23.175: STP: VLAN0001 Fa0/19 -> learning
>
> *Mar 1 00:02:38.175: STP: VLAN0001 sent Topology Change Notice on Fa0/19
>
> *Mar 1 00:02:38.175: STP: VLAN0001 Fa0/19 -> forwarding
>
>
>
> BTW, this is from designated switches perspective towards the root bridge,
> 20 was the original root.
>
>
>
> VLAN0001 32769 000c.ceb4.1780 19 2 20 15 Fa0/19
>
>
>
> All defaults have been used (so my oldest 3550 is the big fat winner and
> PVST+ is the mode)
>
>
>
> -ryan
>
>
>
> *From:* Mike Leske [mailto:mike.leske_at_googlemail.com]
> *Sent:* Saturday, May 09, 2009 4:45 PM
> *To:* Ryan West
> *Cc:* WW)W WWWW W; Anbu; Cisco certification
>
> *Subject:* Re: STP access port start-up delay or intialization to
> forwarding delay
>
>
>
> So, it seems that we have to account for blocking on inter-switch links,
> where we first have to wait for the max-age of the forwarding port to
> expire.
> How do you guys see that?
>
> 2009/5/9 Ryan West <rwest_at_zyedge.com>
>
> I agree 100%, in fact if you turn on debugs to the msec, youbll find that
> itbs 12.000 seconds. Ibm just trying to avoid being wordsmithed for 3
> points during the exam and knowing when I should account for blocking and
> not.
>
>
>
> Labbing it up for the win though!
>
>
>
> -ryan
>
>
>
> *From:* WW)W WWWW W [mailto:eshedalonie_at_gmail.com]
> *Sent:* Saturday, May 09, 2009 4:38 PM
> *To:* Ryan West
> *Cc:* Mike Leske; Anbu; Cisco certification
>
>
> *Subject:* Re: STP access port start-up delay or intialization to
> forwarding delay
>
>
>
> ! Exactly 12 Seconds !
>
> I've Checkd that out With Ping from the computer to the switch.
>
> On Sat, May 9, 2009 at 11:32 PM, WW)W WWWW W <eshedalonie_at_gmail.com>
wrote:
>
> This is My Output
>
>
>
> Show Run | i span
>
> spanning-tree mode pvst
>
> spanning-tree extend system-id
>
> spanning-tree vlan 1 forward-time 6
>
>
>
> Switch#show run int f1/0/12
>
> Building configuration...
>
>
>
> Current configuration : 36 bytes
>
> !
>
> interface FastEthernet1/0/12
>
> end
>
>
>
> Switch#debug spanning-tree events
>
> Spanning Tree event debugging is on
>
> Switch#
>
>
>
> 00:04:18: setting bridge id (which=3) prio 32769 prio cfg 32768 sysid 1
> (on) id
>
> 8001.000f.f7be.7400
>
> 00:04:18: set portid: VLAN0001 Fa1/0/12: new port id 800E
>
> *00:04:18: STP: VLAN0001 Fa1/0/12 -> listening*
>
> 00:04:20: %LINK-3-UPDOWN: Interface FastEthernet1/0/12, changed state to up
>
> 00:04:21: %LINEPROTO-5-UPDOWN: Line protocol on Interface
> FastEthernet1/0/12, ch
>
> anged state to up
>
> *00:04:24: STP: VLAN0001 Fa1/0/12 -> learning*
>
> *00:04:30: STP: VLAN0001 Fa1/0/12 -> forwarding*
>
>
>
> So From Blocking to Listening - 0 Time
>
> Listening to Learning - 6
>
> Learning to Forward - 6
>
>
>
> VLAN0001
>
> Spanning tree enabled protocol ieee
>
> Root ID Priority 32769
>
> Address 000f.f7be.7400
>
> This bridge is the root
>
> Hello Time 2 sec Max Age 20 sec *Forward Delay 6 sec*
>
>
>
> Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
>
> Address 000f.f7be.7400
>
> Hello Time 2 sec Max Age 20 sec *Forward Delay 6 sec*
>
> Aging Time 300
>
>
>
> Interface Role Sts Cost Prio.Nbr Type
>
> ------------------- ---- --- --------- --------
> --------------------------------
>
>
>
> Fa1/0/12 Desg FWD 19 128.14 P2p
>
>
>
>
>
> On Sat, May 9, 2009 at 11:13 PM, Ryan West <rwest_at_zyedge.com> wrote:
>
> Mike,
>
> This is the autoverify output:
>
> ! "show spanning-tree root" on SW1 should look like (Root ID will differ):
>
> Root Hello Max Fwd
> Vlan Root ID Cost Time Age Dly Root Port
> VLAN0001 1 0013.806d.d180 0 2 20 16
> VLAN0100 100 0013.806d.d180 0 2 20 16
> VLAN0145 145 0013.806d.d180 0 2 20 16
>
> (My output is below, thought I would mention this since it's not obvious
> via
> email)
> show spanning-tree root
>
> Root Hello Max Fwd
> Vlan Root ID Cost Time Age Dly Root Port
> ---------------- -------------------- --------- ----- --- --- ------------
> VLAN0001 1 0016.4736.ef80 0 2 20 6
> VLAN0013 13 0016.4736.ef80 0 2 20 6
> VLAN0100 100 0016.4736.ef80 0 2 20 6
> VLAN0145 145 0016.4736.ef80 0 2 20 6
>
> You can't see from here, but I was marked incorrect for using a
> forward-time
> of 6. My sixes have a red line through them.
>
> -ryan
>
> From: Mike Leske [mailto:mike.leske_at_googlemail.com]
> Sent: Saturday, May 09, 2009 4:09 PM
> To: Ryan West
> Cc: Anbu; Cisco certification
>
> Subject: Re: STP access port start-up delay or intialization to forwarding
> delay
>
> Hi Ryan,
>
> why not going with:
>
> spanning-tree vlan x forward-time 6
> 20 + 6 + 6 = 32
>
> Mike
>
> 2009/5/9 Ryan West <rwest_at_zyedge.com<mailto:rwest_at_zyedge.com>>
>
> Anbu,
>
> Thanks for the replay, I understand those phases on paper. What I'm trying
> to
> figure out when this actually happens and what type of wording in a
> question
> might key me to take into account. For example, the ASET lab asks this:
>
> Configure switch 1 as the STP root and set the following parameters:
>
> * Root priority of zero (0)
>
> * An access port start-up delay, due to Spanning Tree, of 32
> seconds.
>
> Which in this case means set the forward-time to 16 seconds and priority of
> associated VLANs to 0. What I'm trying to figure out is when I need to
> account for blocking as well.
>
> -ryan
>
> From: Anbu [mailto:ksanpu_at_gmail.com<mailto:ksanpu_at_gmail.com>]
>
> Sent: Saturday, May 09, 2009 3:29 PM
> To: Ryan West
> Cc: Cisco certification
> Subject: Re: STP access port start-up delay or intialization to forwarding
> delay
>
> From blocking to listening - 20 Sec
> Listening to Learning - 15 sec
> Learning to Forwarding - 15 sec
>
> So total 50 sec.
> On Sat, May 9, 2009 at 7:33 PM, Ryan West
>
> <rwest_at_zyedge.com<mailto:rwest_at_zyedge.com><mailto:rwest_at_zyedge.com<mailto:
> rwe
>
> st_at_zyedge.com>>> wrote:
> Hello,
>
> I was going through some of the ASET exams and I was wondering if someone
> might have some insight on key word detection for an STP question. What
> wording would key you into accounting for blocking time when taking a port
> from <state described in question> to forwarding?
>
> Thanks,
>
> -ryan
>
>
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Received on Sat May 09 2009 - 23:11:48 ART