Definition
Outbound connection slots are the peer links a Bitcoin Core node initiates itself, as opposed to inbound connections it merely accepts. By default a node opens eleven such slots, and the distinction matters for security: outbound peers are the ones you chose from your own address table, so they are far harder for an attacker to control than inbound peers, which anyone on the internet can offer.
The default breakdown
The eleven outbound slots are divided by role. Eight are full-relay connections that exchange transactions, addresses, and blocks. Two are block-relay-only connections that relay only blocks and stay hidden from the public network graph. The remaining one is reserved for a short-lived feeler connection that tests and verifies addresses in the background. This structure deliberately spreads a node's lifeline to the network across several independent channels with different visibility properties.
Why the split matters for resistance
Because the block-relay-only slots are invisible to graph-mapping adversaries and the feeler keeps the verified address pool fresh, an attacker who wants to isolate your node cannot simply target a single, observable set of peers. Bitcoin Core also diversifies outbound peers across distinct networks, so the eight full-relay slots are not all reachable from one autonomous system. Together these choices make a node's outbound peer set both diverse and partly hidden.
Understanding this layout helps a node operator reason about their connectivity. It ties directly to eclipse-attack resistance and to peer eviction logic on the inbound side.
In Simple Terms
Outbound connection slots are the peer links a Bitcoin Core node initiates itself, as opposed to inbound connections it merely accepts. By default a node…