# SENTINEL: arbiter node unreachable, failover delayed for master 'mymaster'

- **ID:** `redis/sentinel-arbiter-unreachable-failover-delayed`
- **Domain:** redis
- **Category:** network_error
- **Verification:** ai_generated
- **Fix Rate:** 82%

## Root Cause

Sentinel cannot connect to the arbiter node (a Redis instance configured as quorum participant) within the failover timeout, preventing the quorum from being reached and delaying failover.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| Redis 6.2.0 | active | — | — |
| Redis 7.0.0 | active | — | — |
| Redis 7.2.0 | active | — | — |

## Workarounds

1. **Check the arbiter's network connectivity using ping and redis-cli -h <arbiter-ip> -p <port> PING, then fix firewall rules or DNS resolution if needed.** (85% success)
   ```
   Check the arbiter's network connectivity using ping and redis-cli -h <arbiter-ip> -p <port> PING, then fix firewall rules or DNS resolution if needed.
   ```
2. **Temporarily adjust the quorum to exclude the arbiter by reducing sentinel monitor mymaster <ip> <port> <quorum> to a lower value (e.g., from 3 to 2) until the arbiter is restored.** (75% success)
   ```
   Temporarily adjust the quorum to exclude the arbiter by reducing sentinel monitor mymaster <ip> <port> <quorum> to a lower value (e.g., from 3 to 2) until the arbiter is restored.
   ```
3. **Ensure the arbiter Redis instance is running with a minimal configuration (e.g., port 26379) and is reachable from all sentinel nodes; verify sentinel.conf for correct arbiter IP.** (80% success)
   ```
   Ensure the arbiter Redis instance is running with a minimal configuration (e.g., port 26379) and is reachable from all sentinel nodes; verify sentinel.conf for correct arbiter IP.
   ```

## Dead Ends

- **** — Increasing sentinel failover timeout (sentinel failover-timeout mymaster 60000) may allow more time but doesn't fix the underlying network or arbiter issue. (60% fail)
- **** — Removing the arbiter from the configuration reduces quorum resilience and may cause split-brain scenarios. (80% fail)
- **** — Restarting the arbiter without checking its network connectivity or configuration will result in the same unreachable state. (70% fail)