This started as a thread on vpp-dev [0].

When examining results for new CSIT tests [1] under gerrit review, we have found that 9000B frames do not propagate through IPsec setup.

One explanation is that IPsec overhead increases frame size above MTU.
In any case, I will try to find the maximal frame size which propagates (both for IPsec and ordinary ip4). So far we know only that frame sizes of 1518B and less do propagate.

[0] https://lists.fd.io/g/vpp-dev/topic/does_ipsec_support_jumbo/16049293?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,16049293
[1] https://gerrit.fd.io/r/#/c/11149/10