PCNE Implementing Hybrid Interconnectivity Practice Question

Exhibit

Refer to the exhibit.

```
# Cloud Router BGP configuration
router bgp 65001
 neighbor 169.254.0.1 remote-as 64512
 neighbor 169.254.0.1 ebgp-multihop 2
 neighbor 169.254.0.1 update-source loopback0
 address-family ipv4 unicast
  neighbor 169.254.0.1 route-map SET-MED in
  neighbor 169.254.0.1 route-map SET-LOCAL-PREF out
!
route-map SET-MED permit 10
 set metric 100
!
route-map SET-LOCAL-PREF permit 10
 set local-preference 200
```

A network engineer configured a Cloud Router with the BGP configuration shown. The on-premises router (AS 64512) is peering with the Cloud Router (AS 65001) over a Dedicated Interconnect VLAN attachment. The engineer notices that traffic from on-premises to Google Cloud is not being routed via this interconnect as expected. What is the most likely cause?

⚠ Common exam trap

Google Cloud often tests the misconception that Cloud Router supports the same BGP commands as a physical Cisco router, leading candidates to overlook the fact that Cloud Router is a managed service with a restricted feature set, particularly regarding interface sourcing and multihop capabilities.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The update-source loopback0 command is invalid for Cloud Router BGP sessions

Cloud Router does not support the `update-source loopback0` command. BGP sessions on Cloud Router must use the primary IP address of the interface that is directly connected to the VLAN attachment; loopback interfaces are not supported for BGP peering. This command would cause the Cloud Router to attempt to source BGP packets from a loopback address that is not reachable by the on-premises router, breaking the BGP session.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
The route-map SET-MED sets the MED attribute incorrectly
Why it's wrong here
MED is valid for eBGP, but the issue is the peering not working.
✗
The ebgp-multihop 2 command is not supported on Cloud Router
Why it's wrong here
Cloud Router supports ebgp-multihop, but it is unnecessary for directly connected peers.
✓
The update-source loopback0 command is invalid for Cloud Router BGP sessions
Why this is correct
Cloud Router requires the BGP session to use the link-local IP address, not a loopback.
✗
The local-preference is set in the outbound direction, which is not allowed
Why it's wrong here
Local preference can be set outbound to influence routes sent to on-premises, but not the root cause.

Visual reference

Go deeper

PCNE Implementing Hybrid Interconnectivity Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

Related to this question