4.1 Multicast II Flashcards
What states are exchanged in MSDP sessions?
S,G
What is the purpose of the MSDP session?
Exchange information about sources between RPs in different domains. Or even within the same domain when used in anycast RP mode.
What is the role of the following protocols in interdomain multicast communication? PIM-SM MSDP MP-BGP
PIM-SM - Builds the MDT, MSDP - Exchanges S,G states between RPs, MP-BGP - Exchanges unicast routes used for RPF
The prefixes announced by MP-BGP do not contain multicast addresses.
True
In interdomain SSM scenarios, there is no need for MSDP.
True
In interdomain SSM scenarios, there is a need for MSDP.
False
MSDP is a dual stack protocol.
False, only v4
__________ provides a solution. The switch listens to IGMP messages on Layer ___, and interprets them silently, to keep track of which host has subscribed to which group.
IGMP snooping, 3
With __________ the switch interprets all Layer 3 PIM messages. This way it learns which router wants to subscribe to which group and can forward the multicast traffic only to the correct ports.
PIM snooping
Multipoint LDP supports the creation of point-to-multipoint as well as multipoint-to-multipoint MDTs.
True
Multipoint LDP does not use the same control and data plane for unicast as for multicast, and thus simplifies operation and troubleshooting in an MPLS core.
False, it uses the same control and data plane.
Label Switching Multicast uses the same control plane as Label Switching Unicast.
True
Consider a group of LSRs connected to the same broadcast domain, which one should send PIM messages towards the backbone?
The DR
(S,G) timers are reset when a packet is forwarded.
True
(*,G) timers are reset when a packet is forwarded.
False
(S,G) timers are reset when a join is forwarded.
True
The *,G state will be created when the LHR receives an IGMP Join.
True
The LHR router will forward PIM messages without a defined RP.
False, without the RP there is no forwarding of PIM messages.
Consider the entry below and answer: Is there an active sender for the group? (*, 224.10.10.10), 00:00:46/00:02:43, RP 10.100.255.4, flags: S Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Ethernet0/2, Forward/Sparse, 00:00:46/00:02:43
No, there is not.
Consider the entry below and answer: Is there an active receiver for the group? (*, 224.10.10.10), 00:00:46/00:02:43, RP 10.100.255.4, flags: S Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Ethernet0/2, Forward/Sparse, 00:00:46/00:02:43
Yes, there is.
Consider the entry below and answer: Is there an active receiver for the group? (10.100.13.1, 224.10.10.10), 00:00:10/00:02:49, flags: PA Incoming interface: Ethernet1/3, RPF nbr 10.100.46.6 Outgoing interface list: Null
No, there is not.
Consider the entry below and answer: Is there an active sender for the group? (10.100.13.1, 224.10.10.10), 00:00:10/00:02:49, flags: PA Incoming interface: Ethernet1/3, RPF nbr 10.100.46.6 Outgoing interface list: Null
Yes, there is.
Consider the entry below and answer: Is there an MDT created? (10.100.13.1, 224.10.10.10), 00:00:10/00:02:49, flags: PA Incoming interface: Ethernet1/3, RPF nbr 10.100.46.6 Outgoing interface list: Null
No
Assume the sender registers before the receiver’s join. When the RP receives the receiver’s join, what PIM message will it originate to receive traffic from the sender?
RP sends PIM join towards the sender to construct the temporary Source Tree.
True or false: The switchover to an SPT is configurable with a bandwidth threshold. ‘If the multicast data traffic is more than x kbit/s, join SPT.’ The default is 100 kbit/s, meaning that the LHR will immediately join the SPT.
True and false. The default is zero kbit/s, meaning that the LHR will immediately join the SPT.
True or false: A threshold of infinity means that the LHR will never join the Shared Tree.
False, it would never join the SPT.
When an LHR receives an IGMP Leave, it originates a prune to the RP and a prune to the FHR.
True. False in part, this is not automatic, the prune is originated as soon as a new multicast packet destined for the receiver arrives.
In an SSM environment, if there are IGMPv2-only capable receivers, it is possible to map multicast groups to specific senders.
True, this allows IGMPv2-only hosts to receive flow in an SSM network.
There are two ways to configure SSM mapping: Dynamic, and Domain Name System (DNS)-based.
False: There are two ways to configure SSM mapping: Static, and Domain Name System (DNS)-based.
In BIDIR-PIM, there is no register message for initial traffic to the RP; from the first packet, the traffic is sent natively.
True
In PIM-ASM, loops are avoided with the Reverse Path Forwarding (RPF) check. In BIDIR-PIM, there is a different mechanism to ensure loop-free forwarding: the Designated Forwarder (DF).
True
In a PIM BiDir scenario, if there are multiple RPs, there will be multiple DFs.
True
What is the main criterion for DF election?
Lowest metric to the RP wins.
What is the purpose of the Tunnel 0 interface created when the RP is configured?
Encapsulate unicast messages from the FHR, for example, to the RP.
In BiDir, the router responsible for forwarding multicast packets received on that network ‘upstream’ to the RP is the ___________
Designated Forwarder
From the DF election messages: ____ : Router announces its metric to the RP, Winner: Router declares itself as DF, ____: RouterA detects another RouterB with a better metric, RouterA remains as DF during the Backoff Timer, Pass: RouterA detects another RouterB with a better metric and passes the DF status to RouterB.
Offer, Backoff
From the DF election messages: Offer : Router announces its metric to the RP, _____: Router declares itself as DF, Backoff: RouterA detects another RouterB with a better metric, RouterA remains as DF during the Backoff Timer, _____: RouterA detects another RouterB with a better metric and passes the DF status to RouterB.
Winner, Pass
