# MongoDB: replSetInitiate quorum check failed: Could not connect to mongo2:27017 / No host described in new configuration 1 for replica set rs0 maps to this node

**Code:** `rs.initiate failed: member not reachable / no host described in new configuration` · **Category:** MongoDB · **Seen on:** MongoDB, Docker

`rs.initiate()`/`rs.add()` couldn't reach a listed member or the config doesn't include the current node's hostname.

## Meaning

Each host in the config must resolve and be reachable from every other member (and listed exactly as it will be addressed). In Docker use service names on one network, not `localhost`. Ensure `bindIp` allows the interface, firewalls permit 27017, and the host in config matches what the node thinks it is (`--bind_ip_all` in containers).

## Common causes

- Hostname not resolvable between members
- bindIp excludes the interface
- localhost used in config
- Firewall blocks 27017
- Member not running yet

## Quick fix

1. Use resolvable hostnames/service names in `rs.initiate`
2. Start all members and verify `nc -vz host 27017` from each
3. Set `--bind_ip_all` in containers

## Detailed fix by platform

### mongosh

1. `rs.initiate({ _id: "rs0", members: [{ _id: 0, host: "mongo1:27017" }, { _id: 1, host: "mongo2:27017" }] })`

## How to diagnose

1. **DNS** — Resolvable?
2. **Reachability** — Port open?
3. **Hostnames** — Match config?

---
Source: [WhatIsMyError](https://whatismyerror.com/errors/mongodb/rs-initiate-host-unreachable)