Cannot make nodes - simple 2-node cluster - talk to each other

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):

Describe the issue:

HI guys.

I’ve only started fiddling with whole ‘opensearch’ thing and I struggle to get two nodes connect, to acknowledge each other’s presence.
Here are config bits which I think are relevant/crucial:

discovery.seed_hosts: [ “10.1.1.100”, “10.1.1.101” ]
cluster.initial_master_nodes: [ “10.1.1.100”, “10.1.1.101” ]
action.auto_create_index: false
plugins.security.disabled: false
network.host: [ local, “10.1.1.100” ]
network.bind_host: [ local, “10.1.1.100” ]
cluster.name: graylog
node.name: ${HOSTNAME}

and:
-> $ curl -X GET https://localhost:9200/_cat/nodes?v -u 'admin:admin' --insecure ip heap.percent ram.percent cpu load_1m load_5m load_15m node.role node.roles cluster_manager name 10.1.1.100 11 98 20 3.17 3.30 3.43 dimr cluster_manager,data,ingest,remote_cluster_client * swir.mine.priv
so it’s own host, on each of the two.

How to troubleshoot this? What am I missing?
many thanks, L.

Configuration:

Relevant Logs or Screenshots: