EC2 MTU & Traffic Drops Diagnostic Troubleshooter
Use the interactive troubleshooter below to identify your EC2 MTU or traffic drop issue by symptom, review the raw error log, understand the root cause, and apply the recommended fix.
🚨 Step 1: What specific error symptom are you experiencing?
Please click the most accurate description:
Quick Reference Table
| # | Scenario | Key Error Signal | Root Cause | The Fix |
|---|---|---|---|---|
| 1 | Jumbo frames silently dropped over internet gateways or VPNs, causing hung connections | pmtu 1500 | Packets larger than 1500 bytes are dropped by intermediate systems because Path MTU Discovery (PMTUD) fails when security groups lack an inbound ICMP rule for Destination Unreachable: Fragmentation Needed. | sudo ip link set dev eth0 mtu 1500 |
| 2 | Packets to/from the instance are dropped and new connections cannot be established | conntrack_allowance_exceeded: 0 | The instance's network traffic exceeded the maximum number of connections that can be tracked by the security group state table. | Scale either the number of instances registered with the load balancer or the size of the instances registered. |
| 3 | Traffic to DNS, IMDS, or Amazon Time Sync Service times out or drops packets | linklocal_allowance_exceeded: 0 | The packet-per-second (PPS) rate of traffic to local proxy services exceeded the maximum allowance for the network interface. | Cache metadata credentials until they approach expiry, or retry queries with an exponential backoff strategy. |