300-170 · Question #162
You plan to use L3Out connections when implementing Layer 3 multicast. Which statement about the router ID configuration is true?
The correct answer is B. The router ID must be configured as a loopback address. When using L3Out connections for Layer 3 multicast in Cisco ACI, the router ID must be configured as a loopback address.
Question
You plan to use L3Out connections when implementing Layer 3 multicast. Which statement about the router ID configuration is true?
Options
- AThe router ID must be unique for each L3Out on the same node in a VRF.
- BThe router ID must be configured as a loopback address.
- CEach node in a VRF must use the same router ID.
- DThe router ID must be an IPv4 address in a range of 224.0.0.0 - 239.255.255.255.
How the community answered
(30 responses)- A3% (1)
- B73% (22)
- C17% (5)
- D7% (2)
Why each option
When using L3Out connections for Layer 3 multicast in Cisco ACI, the router ID must be configured as a loopback address.
The router ID generally needs to be unique per node within a VRF, but the requirement is to use a loopback, not just any unique ID.
For stability and redundancy in L3Out configurations, especially with multicast, the router ID is typically configured using a loopback interface. This ensures the router ID remains up even if a physical interface fails.
Each node in a VRF that participates in routing protocols, especially for L3Outs, should ideally use a unique router ID, not the same one.
The router ID is a unique identifier, typically an IPv4 address, but it must be a unicast address, not a multicast address in the 224.0.0.0-239.255.255.255 range.
Concept tested: ACI L3Out multicast router ID configuration
Source: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/1-x/multicast/multicast_cfg_guide/b_Configuring_Multicast.html
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