4A0-105 - Virtual Private LAN Services
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How many designated ports are there in a spanning tree topology?
1 per segment
MAC explosion is best described as a large amount of MAC addresses being withdrawn and relearned?
What are the advantages of running a physical ring topology with a mesh of mesh-SDPs? (Choose 2)
STP is not required to break the loop because of split-horizon rules.
If the traffic is primarily Unicast, a full mesh of SDPs is a simple and efficient design.
Which of the following statements regarding unicastand multicast frames is true for a traditional layer 2 switch? (Choose 2)
Unicast frames only forward out ports that have a known receiver.
If the FDB is empty, unicast and multicast frames are treated equally.
What needs to be configured in a VPLS in order to forward customer STP BPDUs transparently?
Spanning tree must be disabled within the VPLS.
Which of the following statements about Spanning Tree Protocol is true?
In the case where two switches have the same priority, the switch with the lowest MAC address becomes the root.
In RSTP, an alternate port is on the same switch as a designated Port.
In IEEE 802.1ag, how are loops detected?
The MEP sees its own CFM frames returned to itself.
The following question relates to this command syntax: "config>service# vpls 9000 customer 6 create". Which of the following statements are correct? (Choose 2)
The service-id in this command is 9000.
This value 9000 should be unique across the network as a best practice.
What are the limitations of a traditional layer 2 switch? (Choose 3}
Requires layer 2 loop prevention.
Slow response to topology changes.
Limited to 4094 vlans per switch.
What is the result of initiating an oam mac-ping to an unknown unicast MAC address in a VPLS instance?
The request will be flooded and the only response will come from the PE node that has learned the specified MAC address on a local SAP.
How do user VPLSs become associated with a management VPLS for redundant spoke-sdp connections?
The association is done when the user VPLS is associated with the same sdp-id in the management VPLS
If the max remote-age timer of a B-VPLS is reached, what happens to the remotely learned MAC addresses in the l-VPLS service?
The MAC addresses for the l-VPLS will age out immediately following the remote-age out of the backbone-macs of the B-VPLS.
Which of the following needs to be considered when designing Ethernet networks with redundancy?
Requires a protocol to remove loops.
How does the IEEE 802.1ag loopback function differently from the loopback feature in 802.3ah? (Choose 2)
The loopback function of 802.lag is a non-intrusive "ping" sent from a MEPto a remote MEP or MIP.
The loopback function in 802.3ah is an intrusive test that will loop customer data.
In RSTP, which state do all ports initialize in?
What is the default Spanning Tree protocol used in a VPLS on the Alcatel-Lucent 7750 SR?
Why are provisioning requirements a factor that influence VPLS design? (Choose 2)
Adding or removing a node may require several network touches.
Adding or removing a service may require several network touches.
When ports configured with IEEE 802.3ah EFM are operationally down, what must the device do before declaring the ports are up?
The device will detectthe port change and revert to discovery mode.
Why is MAC explosion a factor to be considered when designing a large VPLS network? (Choose 2)
The time to relearn thousands of MAC addresses may result in excessive flooding or loss of packets.
It could take several seconds to relearn thousands of MAC addresses denying QoS/SLA guarantees.
What is the maximum number of VLANs supported on a traditional Layer 2 switch?
What is the default service-mtu for a VPLS service?
The operation of a VPLS can be best described by which of the following statements?
All of the above.
Which of the following is a function of the data plane that must be considered when provisioning a VPLS service?
Bandwidth and replication requirements.
Why is it best practice to set the bridge priority in an STP network? (Choose 2)
So that you know which links will be active in your network.
To prevent a new switch from becoming root when added to the network.
The "discard-unknown" command has been enabled at the VPLS level. Which of the following statements is true? (Choose 2)
Broadcast traffic will be flooded.
If the unicast DA has not been learned in the FDB,the frame will be dropped.
The FDB has learned 2 MAC addresses. The first is from a device accessible via a locality defined SAP, the second is from a device accessible via an SDP. Both MAC addresses were learned at the exact same time. If all traffic from these hosts stops at the same time, which address will age out first from the FDB based on default settings?
MAC learned via SAP
Which of the following best describes the difference between VPWS and VPLS?
Unlike VPWS, VPLS is a service where customer MAC addresses are learned.
Why should you configure send-flush-on failure on your PE routers when using active/standby pseudowires?
On failure, the PE sends an LDP flush-all-from-me message to all PE devices in the VPLS. This speeds convergence to the new topology.
What action will be taken when an MPLS router receives a frame with a label that does not exist in the LFIB?
The frame will be discarded.
What function in IEEE 802.1 ah helps to limit the amount of MAC addresses learned in the core?
The B-VPLS and l-VPLS are configured in the edge. The B-VPLS is configured with a Backbone MAC and is the only MAC learned in the core
What action will be taken when an Ethernet switch receives a frame with a known DA and an outer Ethertype value of 0x0800 on a dot1q encapsulated port?
The frame will be discarded.
Which of the following describes the overhead added to a customer frame on an Ethernet link in a VPLS service on the Alcatel-Lucent 7750 SR?
The overhead consists of 22 bytes. 14 DLC + 8 for mpls labels
What is PBB also known as?
What must be enabled in order to prevent a loop within a LAG?
What configuration is required on the CE device when using MC-LAG?
The CE must be configured with LACP in active mode.
What scaling factors should a network engineer be aware of when designing VPLS networks? (Choose 3)
Control plane scaling.
Data plane scaling.
IEEE 802.3ah frames must be untagged.
After the "disable-learning" command has been executed at the VPLS level, a new client device originates a frame. What is the result?
The new source MAC addresses will not be entered in the VPLS service forwarding database.
Which of the following technologies allows for two explicit VLAN tags to be received from a customer device?
Which of the following must be true in order to add a port to a LAG? (Choose 2)
ports must have the same speed and duplex settings
autonegotiation must be off or limited
Which of the following statements relating to VPLS is false?
A VPLS on a single node requires a SDP.
An MC-LAG is configured with default parameters. When a failed interface recovers, the active link reverts to the restored interface.
The service-mtu of a VPLS using MPLS encapsulation is set to 9100. What is the minimum MTU value that can be set for the network port if fast re-route facility mode is used on the SDP LSP?
What is the name of the feature supported on the Alcatel-Lucent 7750 SR that prevents MAC explosion in large VPLS deployments?
To reduce the amount of flooding between PE devices which of the following steps should be taken?
Configure the remote age timer to be larger.
How is the Primary Bridge chosen in a VPLS?
The PE devices participating in the VPLS mesh determine which bridge is closest to Root Bridge. This bridge becomes the Primary Bridge.
In Active/Standby pseudowires a failed pseudowire has recovered. Under what circumstances will the active pseudowire revert to the previously failed link?
It will revert if the precedence of the previously failed link is set to 0 or "primary".
How is it possible for multiple services to be carried over the same MPLS LSPs?
Multiple SDPs must be configured and bound to the LSPs for this to be possible.
Which OAM tool can be used to dynamically learn the MAC address of a CE device connected to a SAP within a VPLS service?