We have been having the same issue with Meraki VPN to SonicWALL or Cisco ASA. The tunnel shows active but cannot communicate to the remote network/s. If we have multiple networks, maybe 1 out of 6 will be accessible. Have to manually renegotiate tunnel as a temporary fix. Three weeks ago, Meraki support tech mentioned this can happen if both sides of the tunnel are enabled for NAT-Traversal. Don't know why it's not an issue with any other manufacturers if both sides are enabled but I have learned that any knowledge I have about Networking and security best practices might not be applicable to Meraki Firewalls. Anyways, the Meraki tech disabled the NAT-T for the specific VPN tunnel on the back-end, we're going on three weeks without having to manually renegotiate the tunnel.
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