Linux Advanced Networking Errors: PMTU, conntrack, VLAN, bonding
Working reference for 10 advanced Linux networking issues that show up at scale. PMTU black-hole in tunnels (clamp MSS), conntrack table full on busy NAT/LB boxes (sysctl + timeout tuning), VLAN tag mismatches, bond failover not working (LACP vs active-backup), bridge / STP, NAT masquerade not forwarding, rogue IPv6 RA, ssh slow connect (UseDNS no), asymmetric routing, jumbo frame end-to-end requirements. Cross-linked to networking command reference.