# eth0: jumbo frame dropped, MTU 1500 but frame size 9000 received from 00:1a:2b:3c:4d:5e

- **ID:** `networking/ethernet-jumbo-frame-dropped`
- **Domain:** networking
- **Category:** network_error
- **Verification:** ai_generated
- **Fix Rate:** 88%

## Root Cause

A network interface configured with a standard 1500-byte MTU received an Ethernet frame larger than the MTU (a jumbo frame), typically from a peer that has jumbo frames enabled, causing the kernel to drop the frame due to size mismatch.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| Linux kernel 5.15 | active | — | — |
| Linux kernel 6.6 | active | — | — |
| FreeBSD 13.2 | active | — | — |

## Workarounds

1. **On the sender: ifconfig eth0 mtu 1500** (90% success)
   ```
   On the sender: ifconfig eth0 mtu 1500
   ```
2. **ip link set dev eth0 mtu 9000** (85% success)
   ```
   ip link set dev eth0 mtu 9000
   ```

## Dead Ends

- **Setting the MTU on eth0 to 9000 to accept jumbo frames.** — This may cause fragmentation issues if the path has other devices with lower MTU; also, it changes the interface's behavior for all traffic, not just the problematic peer. (60% fail)
- **Using an access control list to block large frames from the sender.** — Does not solve the root cause; the sender still sends jumbo frames, and blocking them drops legitimate traffic. (80% fail)