Re: Ether Channel Query!!

If a switch doesn't have an entry in its mac-address-table for a
particular destination, it forwards the frame out of all ports
(including port channels) EXCEPT the port it was received on. When
there are loops in the topology, this can cause a storm, as it can keep
coming back around.

Are we agreed so far?

In your case, the frame is received on a port-channel. So, if the switch
doesn't know the destination mac, it will be forwarded out all ports in
that vlan (including other port channels), except the port-channel that
it was received on.

Hey presto, no switching loop.

Regards,
Paul

On 27/09/2010 17:47, HEMANTH RAJ wrote:
> yeah Hammer u right ,But my question is how that LACP/PagP protocols handle
> and sends the traffic to the destination without any formation of loop
>
> In reality if there are two ports which is forwarding and there will be a
> formation of loop,MAC table instability which results in a broadcast storm
> how does it is not happening?
>
>
>
> On Mon, Sep 27, 2010 at 10:12 PM, --Hammer--<bhmccie_at_gmail.com> wrote:
>
>> That's the trick. Both ports are NOT forwarding. The port-channel IS. The
>> port-channel is what STP monitors and places in a forwarding state. It is
>> unaware of the individual ports. On the other side of the cables, the
>> receiving switch is receiving STP on the port-channel. Not on an individual
>> port associated with it. So the STP merely hands instructions to the
>> port-channel interface to send out BPDUs. It doesn't care how they get
>> there. The Port-channel interface (and associated PAGP/LACP protocol) are
>> responsible for getting the BPDU across the wire. STP does not see both
>> ports in a forwarding state.
>>
>> --Hammer--
>>
>>
>> On 9/27/2010 11:36 AM, HEMANTH RAJ wrote:
>>
>> hey Hameer i m asking about loop avoiding mechanism .If both the ports are
>> forwarding and STP is not aware of the both the ports,then thee will be a
>> chance of loop forming on that particular channel
>>
>> On Mon, Sep 27, 2010 at 10:01 PM, --Hammer--<bhmccie_at_gmail.com> wrote:
>>
>>> Someone step in if I mis-quote something.
>>>
>>> You're statement is a bit off. STP is not forwarding on both ports. STP is
>>> forwarding on the port-channel. STP is no longer aware of the individual
>>> ports. How the channel handles STP traffic is a different matter. I don't
>>> think STP sends traffic on both ports in a LACP or PAGP channel. I think the
>>> L2 protos (STP, CDP, DTP, etc) are just passed on the primary link. I'm not
>>> where I can google this to confirm it. Anyone?
>>>
>>> --Hammer--
>>>
>>>
>>> On 9/27/2010 11:25 AM, HEMANTH RAJ wrote:
>>>
>>> Hey If STP has forwarding both ports, then there will be chance of loop
>>> formation
>>> wat is the actual mechanism
>>> how does it prevent loops at the same time it makes all the ports
>>> forwarding
>>>
>>> can anyone explain me?
>>>
>>>
>>> On Mon, Sep 27, 2010 at 8:39 PM, --Hammer--<bhmccie_at_gmail.com> wrote:
>>>
>>>> Thanks Saulat for the quick lab up....
>>>>
>>>> --Hammer--
>>>>
>>>>
>>>>
>>>> On 9/27/2010 9:51 AM, Saulat Ali wrote:
>>>>
>>>>> The bundled ports wont show up in the sh spantree command unless you
>>>>> type in sh span int<physical port> which will show them in forwarding
>>>>> state. As mentioned by Hammer as soon as you put the physical port into
>>>>> an ether channel spanning tree process only shows the logical port in
>>>>> the sh span tree.
>>>>>
>>>>> See below e.g .. port 1/0/52 and 2/0/52 wont show up in the span tree
>>>>> process but you can view their status by entering sh span<vlan> int gig
>>>>> 1/0/52<detail> command,
>>>>>
>>>>> #sh etherchannel summ
>>>>>
>>>>> Group Port-channel Protocol Ports
>>>>> ------+-------------+-----------+---------------------------------------
>>>>> --------
>>>>> 1 Po1(SU) LACP Gi1/0/52(P) Gi2/0/52(P)
>>>>>
>>>>> #sh run int gig 1/0/52
>>>>> Building configuration...
>>>>>
>>>>> Current configuration : 181 bytes
>>>>> !
>>>>> interface GigabitEthernet1/0/52
>>>>> switchport trunk encapsulation dot1q
>>>>> switchport mode trunk
>>>>> switchport nonegotiate
>>>>> channel-group 1 mode active
>>>>> end
>>>>>
>>>>> #sh run int gig 2/0/52
>>>>> Building configuration...
>>>>>
>>>>> Current configuration : 181 bytes
>>>>> !
>>>>> interface GigabitEthernet2/0/52
>>>>> switchport trunk encapsulation dot1q
>>>>> switchport mode trunk
>>>>> switchport nonegotiate
>>>>> channel-group 1 mode active
>>>>> end
>>>>>
>>>>> #sh run int po1
>>>>> Building configuration...
>>>>>
>>>>> Current configuration : 144 bytes
>>>>> !
>>>>> interface Port-channel1
>>>>> switchport trunk encapsulation dot1q
>>>>> switchport mode trunk
>>>>> switchport nonegotiate
>>>>> end
>>>>>
>>>>>
>>>>> #sh span vlan 2
>>>>> VLAN0002
>>>>> Spanning tree enabled protocol rstp
>>>>> Root ID Priority 24578
>>>>> Address 0022.be9f.ab80
>>>>> This bridge is the root
>>>>> Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
>>>>>
>>>>> Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
>>>>> Address 0022.be9f.ab80
>>>>> Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
>>>>> Aging Time 300
>>>>>
>>>>> Interface Role Sts Cost Prio.Nbr Type
>>>>> ---------------- ---- --- --------- --------
>>>>> --------------------------------
>>>>> Po1 Desg FWD 3 128.616 P2p
>>>>>
>>>>>
>>>>> #sh spanning-tree vlan 2 int gi2/0/52 de
>>>>> Port 616 (Port-channel1) of VLAN0002 is designated forwarding
>>>>> Port path cost 3, Port priority 128, Port Identifier 128.616.
>>>>> Designated root has priority 24578, address 0022.be9f.ab80
>>>>> Designated bridge has priority 24578, address 0022.be9f.ab80
>>>>> Designated port id is 128.616, designated path cost 0
>>>>> Timers: message age 0, forward delay 0, hold 0
>>>>> Number of transitions to forwarding state: 1
>>>>> Link type is point-to-point by default
>>>>> BPDU: sent 25045070, received 73
>>>>>
>>>>> #sh spanning-tree vlan 2 int gig1/0/52 de
>>>>> Port 616 (Port-channel1) of VLAN0002 is designated forwarding
>>>>> Port path cost 3, Port priority 128, Port Identifier 128.616.
>>>>> Designated root has priority 24578, address 0022.be9f.ab80
>>>>> Designated bridge has priority 24578, address 0022.be9f.ab80
>>>>> Designated port id is 128.616, designated path cost 0
>>>>> Timers: message age 0, forward delay 0, hold 0
>>>>> Number of transitions to forwarding state: 1
>>>>> Link type is point-to-point by default
>>>>> BPDU: sent 25045075, received 73
>>>>>
>>>>> #sh spanning-tree vlan 2 int po1 de
>>>>> Port 616 (Port-channel1) of VLAN0002 is designated forwarding
>>>>> Port path cost 3, Port priority 128, Port Identifier 128.616.
>>>>> Designated root has priority 24578, address 0022.be9f.ab80
>>>>> Designated bridge has priority 24578, address 0022.be9f.ab80
>>>>> Designated port id is 128.616, designated path cost 0
>>>>> Timers: message age 0, forward delay 0, hold 0
>>>>> Number of transitions to forwarding state: 1
>>>>> Link type is point-to-point by default
>>>>> BPDU: sent 25045080, received 73
>>>>>
>>>>> -----Original Message-----
>>>>> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>>>>> CCIE KID
>>>>> Sent: 27 September 2010 15:29
>>>>> To: --Hammer--
>>>>> Cc: ccielab_at_groupstudy.com
>>>>> Subject: Re: Ether Channel Query!!
>>>>>
>>>>> Hey can u explain me the process and what r the packets exchanged so
>>>>> that
>>>>> how does STP come to know that that the particular port is bundled
>>>>>
>>>>> What will be in the sh spanning-tree detail for that particular port
>>>>> which
>>>>> is been blocking
>>>>> Whether it will be of forwarding state
>>>>>
>>>>> That bundled link will be in which state in forwarding state in STP ah??
>>>>> pls brief me about that??
>>>>>
>>>>> On Mon, Sep 27, 2010 at 7:51 PM, --Hammer--<bhmccie_at_gmail.com> wrote:
>>>>>
>>>>> CCIE KID,
>>>>>> When you "bond" the two physical interfaces into a logical port
>>>>>>
>>>>> channel,
>>>>>
>>>>>> you will pass traffic over both Fa0/1 and Fa0/2. STP treats the entire
>>>>>> collection of physical interfaces as a single logical port. This is
>>>>>>
>>>>> all
>>>>>
>>>>>> negotiated between the endpoints. Does that help?
>>>>>>
>>>>>> --Hammer--
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 9/27/2010 9:17 AM, CCIE KID wrote:
>>>>>>
>>>>>> I have a doubt in ether Channel
>>>>>>>
>>>>>>> This is my scenario
>>>>>>>
>>>>>>> SW1 fa0/1-------------------------------------------fa 0/1 SW2
>>>>>>> fa0/2-------------------------------------------fa 0/2
>>>>>>>
>>>>>>> In STP SW1 is the root bridge and SW2 is the non root bridge , In SW2
>>>>>>>
>>>>>> fa
>>>>>
>>>>>> 0/1
>>>>>>> is in forwarding state and fa 0/2 is in blocking state .
>>>>>>> So in Ether channel, if we bundle fa0/1 and fa 0/2 ,traffic cannot be
>>>>>>> passed
>>>>>>> through fa 0/2 .
>>>>>>> How Ether Channel informs STP about the bundling and makes the fa 0/2
>>>>>>>
>>>>>> into
>>>>>
>>>>>> forwarding
>>>>>>> Can anyone explain me the process
>>>>>>> I am expecting the experts to explain
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> With Warmest Regards,
>>>>>>>
>>>>>>> CCIE KID
>>>>>>> IN PURSUIT OF CCIE
>>>>>>>
>>>>>>>
>>>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>>>
>>>>>>>
>>>>>>>
>>>>> _______________________________________________________________________
>>>>>
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>>>>>> _______________________________________________________________________
>>>>>
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>>>>>>
>>>>>
>>>>
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Problems arise Bcoz we talk,prblms r not solve bcoz we dont talk So gud r
>>> bad talk to ur affectionate one's freely
>>>
>>> Urs Friendly,
>>> HP HEMANTH RAJ
>>>
>>>
>>
>>
>> --
>> Problems arise Bcoz we talk,prblms r not solve bcoz we dont talk So gud r
>> bad talk to ur affectionate one's freely
>>
>> Urs Friendly,
>> HP HEMANTH RAJ

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Received on Mon Sep 27 2010 - 18:06:01 ART