Trying to determine if we could even get jumbo frames all the way from an EC2 instance in a VPC connected to a TGW back to a customer CNF via Direct Connect.

Question

We know Direct Connect and the DX Gateway can support Jumbo Frame (8500 for Transit Virtual Interface/9001 for Private Virtual interface), but does the TGW to VPC peering connection support Jumbo Frames? Trying to determine if we could even get jumbo frames all the way from an EC2 instance in a VPC connected to a TGW back to a customer CNF via Direct Connect.

Accepted Answer

1. Transit Gateway maintains a uniform MTU of 8500 across all attachments.
2. Packets larger than 8500 arriving at the TGW are silently dropped.
3. TGW does not generate FRAG_NEEDED ICMP packets at this time. As a result PMTUD does not work.
4. TGW enforces MSS clamping for all TCP SYN and SYN-ACKs passing through it.
5. For VPN attachments, MSS is clamped at 1500.

Taking that information into consideration, I would suggest that you conduct your tests. To answer your question, you should be able to transit 8500 byte packets through the system.

Trying to determine if we could even get jumbo frames all the way from an EC2 instance in a VPC connected to a TGW back to a customer CNF via Direct Connect.

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