Network & Infrastructure / Linux Networking & Host Performance
Neighbor-table pressure in dense host and container networks
New neighbors fail to resolve on a dense node while established endpoints remain reachable. Neighbor-table pressure can become a constraint before address space or link bandwidth is exhausted.
Environment and inputs: Linux network namespaces, host routing and network drivers; availability and semantics depend on kernel and driver versions. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Collect neighbor counts by state, allocation or garbage-collection warnings, interface scope and workload endpoint churn. Distinguish IPv4 ARP from IPv6 neighbor behavior and check namespace boundaries.
Explain the result
Neighbor state is a finite host resource with lifecycle and garbage-collection behavior. Increasing limits can help justified scale, but uncontrolled churn or a large flat domain may remain the actual cause.
Plan the fix
Reduce unnecessary adjacency scope and size supported neighbor capacity using measured peak state and memory. Fix duplicate or abandoned endpoint provisioning that creates unbounded churn.
Check the result and rollback
Validate new endpoint resolution under peak creation rate and failover. Restore prior limits if memory pressure grows or the change leaves persistent unresolved entries without improving service reachability.