A network engineer configured an Ethernet switch using these commands.
Switchone(config) # Spanning-tree portfast bpdufilter default
Which statement about the spanning-tree portfast feature on the switch is true?
A.
If an interface is enabled for portfast receives BDPU, the port goes through the spanning-tree
listening, learning, and forwarding states.
B.
If an interface is enabled for portfast receives BDPU, the port does not go through the
spanning-tree listening, learning, and forwarding states.
C.
If an interface is enabled for portfast receives BDPU, the port is shut down immediately.
D.
If an interface is enabled for portfast receives BDPU, the port goes into the spanning-tree
inconsistent state.
I’d disagree and say C here.
spanning-tree bpduguard enable (Puts port in errdisable upon receiving any bpdu). https://supportforums.cisco.com/document/45136/importance-bpdu-guard-and-bpdu-filter
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Port is shutdown (err-disable) if it has bpduguard enabled and it receives a bpdu.
With bpdufilter as described here the bpdu is ignored and the port forwards immediately. Portfast causes it to bypass the normal spanning tree states.
So B is correct. That is not a desirable result though.
BPDUfilter is dangerous to the stability of your network. BPDU’s are there for a reason.
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In his link, it says
Global mode
spanning-tree portfast bpdufilter default (It enables bpdufiltering on ports that have port-fast configuration, so it sends a few bpdu while enabling port then it filters bdpu unless receives a bpdu, after that it changes from port-fast mode and disables filtering for port to operate like a normal port because it has received bpdu).
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It’s not bpduguard but bpdufilter which is configured here
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STP PortFast causes a Layer 2 LAN interface configured as an access port to enter the forwarding state immediately, bypassing the listening and learning states. However, the “Spanning-tree portfast bpdufilter default” command specifies that if a BPDU is received on that port, then the default action of STPof listening, learning, and forwarding states should be used.
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As per the literature I have read, the use of ‘default’ keyword in the command specifies that IF a BPDU is received on that port, then go through all three stages/states of the normal feature. So to sum it up, I think (just a thought) that network administrator gave this command as an insurance policy, that if someone attaches another switch or device which has potential to cause loops in the topology ON THIS SPECIFIC PORT/INTERFACE; then the whole STP theorem will be applied on it.
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The BPDU filtering feature can be globally enabled on the switch or can be enabled per interface, but the feature operates with some differences.
At the global level, you can enable BPDU filtering on Port Fast-enabled interfaces by using the spanning-tree portfast bpdufilter default global configuration command. This command prevents interfaces that are in a Port Fast-operational state from sending or receiving BPDUs. The interfaces still send a few BPDUs at link-up before the switch begins to filter outbound BPDUs. You should globally enable BPDU filtering on a switch so that hosts connected to these interfaces do not receive BPDUs. If a BPDU is received on a Port Fast-enabled interface, the interface loses its Port Fast-operational status, and BPDU filtering is disabled.
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3560/software/release/12-2_55_se/configuration/guide/3560_scg/swstpopt.html
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Best Regards!
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New Question 3
A & E right
The actions are shutdown and trap
storm-control action shutdown
storm-control action trap
New Question 5
D is the right answer.
VRRP multicast is 224.0.0.18
VRRP mac address is 0000.5e00.01xx ( xx is vrrp group)
HSRP mac address is 0000.0c07,acxx (xx is standby group)
HSRP multicast is 224.0.0.2
HSRP UDP port 1985
GLBP mulitcast is 224.0.0.102
GLBP mac address is 0007.b4xx.xxyy( xxxx is six zero bit followed by 10 digit group , yy is the virtual forwarder)
GLBP port is 3222
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