VPC peering concept in AWS - Step-by-Step Execution

Process Flow - VPC peering concept

Create VPC A

↓

Request Peering

→Accept Peering

↓

Peering Active

↓

Update Route Tables

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Traffic Allowed Between VPCs

Two VPCs are created separately. One requests peering, the other accepts. Once active, route tables are updated to allow traffic between them.

Execution Sample

AWS

1. Create VPC A and VPC B
2. VPC A sends peering request to VPC B
3. VPC B accepts peering request
4. Update route tables in both VPCs
5. Traffic flows between VPC A and VPC B

This sequence shows how two VPCs connect via peering to enable communication.

Process Table

Step	Action	State Change	Result
1	Create VPC A	VPC A exists	VPC A ready
2	Create VPC B	VPC B exists	VPC B ready
3	VPC A sends peering request	Peering request pending	Waiting for acceptance
4	VPC B accepts peering	Peering connection active	Peering established
5	Update route tables	Routes added to VPC A and B	Traffic allowed between VPCs
6	Test traffic flow	Packets sent between VPCs	Communication successful

💡 Peering active and routes updated, so traffic flows between VPCs

Status Tracker

Variable	Start	After Step 3	After Step 4	After Step 5	Final
VPC A	Not created	Exists	Exists	Exists	Exists
VPC B	Not created	Exists	Exists	Exists	Exists
Peering Connection	None	Pending	Active	Active	Active
Route Tables	No peering routes	No peering routes	No peering routes	Routes added	Routes added
Traffic Flow	Blocked	Blocked	Blocked	Allowed	Allowed

Key Moments - 3 Insights

Why can't VPCs communicate immediately after peering request is sent?

Because the peering connection is only pending (see step 3 in execution_table). It must be accepted (step 4) and routes updated (step 5) before traffic flows.

What happens if route tables are not updated after peering is active?

Traffic will still be blocked because route tables control network paths (see step 5 and 6). Updating routes is essential for communication.

Can VPC peering connect VPCs in different AWS accounts?

Yes, but the peering request and acceptance must be done across accounts. The flow remains the same as shown in the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, at which step does the peering connection become active?

A Step 4

B Step 5

C Step 3

D Step 6

💡 Hint

Check the 'State Change' column for when peering connection status changes to active.

According to variable_tracker, what is the state of 'Traffic Flow' after step 4?

A Allowed

B Blocked

C Pending

D Unknown

💡 Hint

Look at the 'Traffic Flow' row under 'After Step 4' column.

If route tables are not updated, what will be the result in step 6?

A Traffic allowed between VPCs

B Peering connection fails

C Traffic blocked despite active peering

D VPCs get deleted

💡 Hint

Refer to key_moments about route tables and execution_table step 5 and 6.

Concept Snapshot

VPC Peering connects two VPCs to enable private communication.
One VPC requests peering; the other accepts.
Peering becomes active after acceptance.
Route tables must be updated to allow traffic.
Traffic flows only after routes are set.
Peering works within or across AWS accounts.

Full Transcript

VPC peering allows two separate virtual networks (VPCs) to connect privately. First, both VPCs are created. Then, one VPC sends a peering request to the other. The second VPC must accept this request. Once accepted, the peering connection becomes active. However, to enable communication, route tables in both VPCs need to be updated to include routes pointing to the other VPC. Only after these updates can traffic flow between the VPCs. If route tables are not updated, even an active peering connection will not allow traffic. This process works for VPCs in the same or different AWS accounts.