Why Is My Mining Rig Getting Rejected Shares?

Understanding Rejected Shares in Cryptocurrency Mining

1. Rejected shares occur when a mining rig submits a solution to the pool that fails validation due to incorrect formatting, expired job parameters, or network latency.

2. The Stratum mining protocol expects precise adherence to timestamp (ntime), difficulty targets, and block header structure—deviations trigger immediate rejection.

3. GPU mining rigs with unstable overclocking settings frequently generate invalid nonces, causing the pool server to discard those shares without reward attribution.

4. Misconfigured miner software may send stale work after a new block is found, especially if ntime rolling is disabled or improperly implemented on the client side.

5. Network jitter between the rig and the pool can corrupt data packets during submission, resulting in malformed share payloads that violate Stratum’s binary framing rules.

Hardware-Related Causes of Share Rejection

1. A failing power supply unit (PSU) introduces voltage fluctuations that destabilize GPU clock domains, leading to computational errors during hash generation.

2. Overheating GPUs suffer from thermal throttling or silent compute corruption, producing hashes that pass local validation but fail remote consensus checks.

3. Memory timing mismatches on motherboards supporting multiple GPUs cause intermittent PCIe packet loss, disrupting Stratum job acknowledgments.

4. Aging capacitors on GPU PCBs degrade signal integrity, increasing bit-flip rates during intensive kernel execution used in Ethash or KawPoW algorithms.

5. Incompatible BIOS versions on AMD Radeon cards have been observed to misreport memory bandwidth usage, triggering false positive invalid share flags in pool-side diagnostics.

Software and Configuration Factors

1. Outdated mining software may not support newer Stratum extensions like mining.notify_v2, causing mismatched job parsing and rejected submissions.

2. Incorrectly set --max-diff or --diff-multiplier flags force the miner to target inappropriate difficulty levels, generating shares outside the pool’s accepted range.

3. MultiPoolMiner’s watchdog timer marks miners as failed when the ratio of accepted to bad shares exceeds a threshold—this behavior is logged but often mistaken for external rejection.

4. Using unsupported command-line arguments with closed-source miners like PhoenixMiner or T-Rex can silently override Stratum handshake parameters, breaking compatibility with modern pool servers.

5. Custom kernel patches applied to open-source miners sometimes bypass nonce-range validation logic, submitting values that violate Bitcoin or Ethereum consensus rules.

Network Infrastructure Issues

1. Carrier-grade NAT traversal in residential ISP environments prevents reliable TCP keep-alive handshakes, leading to abrupt disconnections and orphaned share submissions.

2. DNS-based load balancing across geographically distributed pool endpoints causes inconsistent job distribution, resulting in duplicate or outdated work assignments.

3. TLS termination proxies inserted by corporate firewalls strip Stratum-specific headers such as X-Stratum-Session-ID, forcing pools to treat valid submissions as anonymous and unverifiable.

4. IPv6-only network stacks interacting with IPv4-only mining pools create asymmetric routing paths where share acknowledgments never reach the rig.

5. QoS policies on consumer routers prioritize HTTP/HTTPS traffic over raw TCP connections, starving Stratum sessions of bandwidth during peak network congestion.

Frequently Asked Questions

Q: Can rejected shares affect my rig’s hashrate reporting?Yes. Most mining dashboards calculate effective hashrate using only accepted shares. High rejection rates artificially deflate displayed performance metrics even if raw GPU throughput remains unchanged.

Q: Does MultiPoolMiner automatically switch pools when rejection rates rise?It triggers pool switching only when the configured acceptance ratio falls below the failure threshold—not based solely on rejection count. The tool evaluates profitability including power cost and pool fee structures before initiating migration.

Q: Why do some pools report “duplicate” instead of “rejected” for the same share?Duplicate labeling occurs when two identical shares arrive within milliseconds via different network paths. Pools use deterministic deduplication logic to accept the first and label subsequent ones as duplicates—this is distinct from cryptographic invalidity.

Q: Is there a way to log raw share payloads for forensic analysis?Yes. Enabling verbose logging in Claymore’s Dual Miner or lolMiner exposes hex-encoded share submissions. These payloads can be parsed against Stratum specification documents to isolate protocol-level deviations.