VPC Peering traffic volume mismatch between origin and destination VPC

Question

My customer is looking to move from VPC Peering to Transit Gateway, and as part of their preparation for cost analysis started to measure the traffic flow between VPC's. They have observed that the egress traffic from one VPC does not match the ingress at the destination.

eg.

Outbound eu-west-1 = 232.4Gb

Inbound eu-central-1 = 342Gb

The variance is seemingly random between peered endpoints.  Can anyone account for this or have a way to diagnose? Unfortunately, VPC Flow Logs are out (I believe) as these are cross account VPC peers.

Accepted Answer

If these are cross-account peering, one part of the charges would be at the other account.

If the customer have CUR enable, they can use this query, modify the table name, to drill-down on the peering charges:

SELECT DISTINCT
         "line_item_product_code"
       , "bill_billing_period_start_date"
       , "bill_payer_account_id"
       , "product_product_name"
       , "line_item_line_item_type"
       , "line_item_operation"
       , "product_region"
       , "line_item_usage_type"
       , "product_from_location"
       , "product_to_location"
       , "line_item_resource_id"
       , ("sum"("line_item_usage_amount") / 1024) "TB's"
       , "sum"("line_item_blended_cost") "cost"
       FROM
         customer_cur_data.customer_all
       WHERE "line_item_operation" LIKE '%VPCPeering%'
       GROUP BY "line_item_product_code", "bill_billing_period_start_date", "bill_payer_account_id", "product_product_name", "line_item_line_item_type", "line_item_operation", "product_region", "line_item_usage_type", "product_from_location", "product_to_location", "line_item_resource_id"

VPC Peering traffic volume mismatch between origin and destination VPC

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