A company is planning to migrate to AWS and use multiple VPCs in multiple AWS Regions. A network engineer must connect the eu-west-1 and eu- central-1 Regions to the company headquarters and branch…

Question

Options

• AModify the IP address of the peering attachment to a wider range.
• BDelete the static routes that were in the transit gateway route table to send traffic to the remote
• CCreate a new route destined to 10.0.0.0/8 in both production VPC route tables with the Region
• DModify the transit gateway route tables from the production accounts to propagate routes

• A
  12% (8)
• B
  2% (1)
• C
  80% (52)
• D
  6% (4)

Explanation

Explanation

Option C is correct because the VPC route tables in each Region need explicit routes pointing to the remote VPC's CIDR range, using the local transit gateway as the next hop. Without entries in the VPC route tables directing traffic destined for the remote VPC (10.0.0.0/8 covers both 10.0.0.0/16 and 10.1.0.0/16) toward the transit gateway, traffic from the instances never leaves the local VPC - regardless of how well the transit gateway peering is configured. Step 7 only mentions activating propagation, which doesn't automatically add routes pointing to the transit gateway from the VPC subnet route tables.

• Option A is wrong because peering attachments don't have "IP addresses" to modify - they are logical constructs, and widening a CIDR on a peering attachment is not a valid operation.
• Option B is wrong because removing the static routes in the transit gateway route tables would break inter-Region routing, since peering attachments don't support dynamic route propagation between transit gateways - static routes are required.
• Option D is wrong because transit gateway peering attachments do not support route propagation - routes across peered transit gateways must always be added as static routes.

Memory Tip: Think of routing as a two-layer problem - the transit gateway layer (TGW route tables) and the VPC layer (subnet route tables). Both layers must have routes configured; fixing one without the other leaves traffic with "nowhere to go" at the VPC boundary.

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