MTU Question for direct link

Question

We have a direct connection to AWS from our premises. VIF is configured with MTU 1500. But I pinged from our Premises with a Jumbo frame, it passed through. I do not understand why.
The following is captured from the firewall
[fw:0]# tcpdump -r gongya-ping-mtu.pcap -vvv
reading from file gongya-ping-mtu.pcap, link-type EN10MB (Ethernet)
23:06:54.535196 IP (tos 0x0, ttl 56, id 0, offset 0, flags [DF], proto ICMP (1), length 7998)
    ip-10-146-40-39.us-west-2.compute.internal > ip-10-71-149-159.us-west-2.compute.internal: ICMP echo request, id 151, seq 1, length 7978
23:06:54.535478 IP (tos 0x0, ttl 55, id 0, offset 0, flags [DF], proto ICMP (1), length 7998)
    ip-10-146-40-39.us-west-2.compute.internal > ip-10-71-149-159.us-west-2.compute.internal: ICMP echo request, id 151, seq 1, length 7978
23:06:54.537350 IP (tos 0x0, ttl 253, id 5705, offset 0, flags [none], proto ICMP (1), length 7998)
    ip-10-71-149-159.us-west-2.compute.internal > ip-10-146-40-39.us-west-2.compute.internal: ICMP echo reply, id 151, seq 1, length 7978
23:06:54.537390 IP (tos 0x0, ttl 252, id 5705, offset 0, flags [none], proto ICMP (1), length 7998)

Accepted Answer

The packet capture, (which is extremely hard to read you should format it with the inline code feature in the re:Post editor window)  is showing what seems to be ICMP echo request/response within AWS:

ip-10-71-149-159.us-west-2.compute.internal > ip-10-146-40-39.us-west-2.compute.internal
ip-10-146-40-39.us-west-2.compute.internal > ip-10-71-149-159.us-west-2.compute.internal

You seem to be pinging from 10.71.149.159 to 10.146.40.39 ?  Given that a VPC is a maximum of a /16 this seems to be between hosts on two different VPCs?  Inside of VPCs you can support up to 9001 byte MTUs and over Transit Gateway's 8500.

MTU Question for direct link

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