Bitcoin Core 27.0 which enables v2 transport (BIP324) by default was released a few days ago. I'm already seeing a few peers with the /Satoshi:27.0.0/ user agent and all of them have the P2P_V2 service flag set. However, one of the peers (inbound) is connected over a v1 connection. Is this evidence of network tampering (as failed v2 connections retry as v1), or could there be another reason?

  • What version are you running?
    – Murch
    Commented Apr 24 at 13:47
  • 27.0, but I don't think there's any difference from 26.0 with respect to BIP324 except for the changed default, right? Commented Apr 24 at 14:18

1 Answer 1


Even if both peers support BIP324, the initiator of the connection might not have known that the acceptor did. Bitcoin Core (as of v27) has downgrading logic (i.e., it will retry with v1 if a v2 connection fails in some circumstances), but no upgrade logic (it will not automatically reconnect when a v1 peer tells it it supports v2).

My best guess is simply that your peer did not have up-to-date "addr" information about your node.

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