QUESTION: 21

Exhibit

Referring to the exhibit, PIM-SM is configured on all routers, and Anycast-RP with Anycast-PIM is used for the discovery mechanism on RP1 and RP2. The interface metric values are shown for the OSPF area.
In this scenario, which two statements are correct about which RP is used? (Choose two.)

Source2 will use RP2 and Received will use RP2 for group 224.2.2.2.
Source2 will use RP1 and Receiver2 will use RP1 for group 224.2.2.2.
Source1 will use RP1 and Receiver1 will use RP1 for group 224.1.1.1.
Source1 will use RP1 and Receiver1 will use RP2 for group 224.1 1 1

Answer(s): A,C

Explanation:

A sham link is a logical link between two PE routers that belong to the same OSPF area but are connected through an L3VPN. A sham link makes the PE routers appear as if they are directly connected, and prevents OSPF from preferring an intra-area back door link over the VPN backbone. A sham link creates an OSPF multihop neighborship between the PE routers using TCP port 646. The PEs exchange Type 1 OSPF LSAs instead of Type 3 OSPF LSAs for the L3VPN routes, which allows OSPF to use the correct metric for route selection1.

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QUESTION: 22

Exhibit

Referring to the exhibit, which three statements are correct about route 10 0 0.0/16 when using the default BGP advertisement rules'? (Choose three.)

R1 will prepend AS 65531 when advertising 10 0.0 0/16 to R2.
R1 will advertise 10.0.0.0/16 to R2 with 192 168 1 1 as the next hop.
R2 will advertise 10.0.0.0/16 to R3 with 192.168.1 1 as the next hop
R4 will advertise 10 0.0 0/16 to R6 with 172.16 1 1 as the next hop
R2 will advertise 10.0.0.0/16 to R4 with 172.16.1.1 as the next hop

Answer(s): B,D,E

Explanation:

The problem in this scenario is that R1 and R8 are not receiving each other's routes because of private AS numbers in the AS path. Private AS numbers are not globally unique and are not advertised to external BGP peers. To solve this problem, you need to do the following:
Configure loops on routers in AS 65412 and advertise-peer-as on routers in AS 64498. This allows R5 and R6 to advertise their own AS number (65412) instead of their peer's AS number (64498) when sending updates to R7 and R8. This prevents a loop detection issue that would cause R7 and R8 to reject the routes from R5 and R6.
Configure remove-private on advertisements from AS 64497 toward AS 64498 and from AS 64500 toward AS 64499. This removes any private AS numbers from the AS path before sending updates to external BGP peers. This allows R2 and R3 to receive the routes from R1 and R4, respectively.

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QUESTION: 23

Which two statements describe PIM-SM? (Choose two)

Routers with receivers send join messages to their upstream neighbors.
Routers without receivers must periodically prune themselves from the SPT.
Traffic is initially flooded to all routers and an S,G is maintained for each group
Traffic is only forwarded to routers that request to join the distribution tree.

Answer(s): A,D

Explanation:

PIM sparse mode (PIM-SM) is a multicast routing protocol that uses a pull model to deliver multicast traffic. In PIM-SM, routers with receivers send join messages to their upstream neighbors toward a rendezvous point (RP) or a source-specific tree (SPT). The RP or SPT acts as the root of a shared distribution tree for a multicast group. Traffic is only forwarded to routers that request to join the distribution tree by sending join messages. PIM-SM does not flood traffic to all routers or prune routers without receivers, as PIM dense mode does.

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QUESTION: 24

Which statement is true regarding BGP FlowSpec?

It uses a remote triggered black hole to protect a network from a denial-of-service attack.
It uses dynamically created routing policies to protect a network from denial-of-service attacks
It is used to protect a network from denial-of-service attacks dynamically
It verifies that the source IP of the incoming packet has a resolvable route in the routing table

Answer(s): B

Explanation:

BGP FlowSpec is a feature that extends the Border Gateway Protocol (BGP) to enable routers to exchange traffic flow specifications, allowing for more precise control of network traffic. The BGP FlowSpec feature enables routers to advertise and receive information about specific flows in the network, such as those originating from a particular source or destined for a particular destination. Routers can then use this information to construct traffic filters that allow or deny packets of a certain type, rate limit flows, or perform other actions1. BGP FlowSpec can also help in filtering traffic and taking action against distributed denial of service (DDoS) attacks by dropping the DDoS traffic or diverting it to an analyzer2. BGP FlowSpec rules are internally converted to equivalent Cisco Common Classification Policy Language (C3PL) representing corresponding match and action parameters2. Therefore, BGP FlowSpec uses dynamically created routing policies to protect a network from denial-of-service attacks.

Reference:

1: https://www.networkingsignal.com/what-is-bgp-flowspec/
2: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16/irg-xe-16- book/bgp-flowspec-route-reflector-support.html

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QUESTION: 21

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QUESTION: 22

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QUESTION: 23

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QUESTION: 24

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