AdguardTeam/AdGuardHome · error

another client uses the same MAC

Error message

another client %q uses the same MAC %q

What it means

Thrown when a client's MAC address is already assigned to another client in the index. MAC addresses uniquely identify persistent clients. The error reports the existing client name and the duplicated MAC.

Solutions

1. Search stored clients for the MAC in the message and remove it from one of them (often a stale manually-added client)
2. Let the DHCP/ARP runtime source own the MAC and delete the manual duplicate
3. Pre-normalize the client list so MACs are unique before Add

Example fix

// before
client.MACs = []string{"AA:BB:CC:DD:EE:FF"} // already on client "phone"
s.Add(ctx, client)

// after
client.MACs = nil
s.Add(ctx, client)

usedMACs := map[string]string{}
for _, p := range existing {
    for _, m := range p.MACs { usedMACs[strings.ToLower(m)] = p.Name }
}
for _, m := range c.MACs {
    if owner, ok := usedMACs[strings.ToLower(m)]; ok && owner != c.Name { /* clash */ }
}

if err := s.Add(ctx, c); err != nil && strings.Contains(err.Error(), "uses the same MAC") { c.MACs = nil; _ = s.Add(ctx, c) }

When it happens

Trigger: Calling Storage.Add or Storage.Update with a client whose MAC equals the MAC of a different stored client, detected by clashesMAC.

Common situations: Two client entries (e.g. one from DHCP, one manual) carrying the same MAC, cloning client configs in the UI, imported client lists with duplicate MACs.

Related errors

• another client uses the same ClientID
• another client uses the same IP
• another client uses the same subnet
• invalid tag
• invalid upstream servers

AI-assisted analysis of AdguardTeam/AdGuardHome@b41aefbe51 (2026-08-27). Data as JSON: /api/errors/ac36c02a262e2edd. Report an issue: GitHub.

Appendix: source

Thrown at internal/client/index.go:133

			p := ci.uidToClient[existing]

			return fmt.Errorf("another client %q uses the same ClientID %q", p.Name, id)
		}
	}

	p, ip := ci.clashesIP(c)
	if p != nil {
		return fmt.Errorf("another client %q uses the same IP %q", p.Name, ip)
	}

	p, s := ci.clashesSubnet(c)
	if p != nil {
		return fmt.Errorf("another client %q uses the same subnet %q", p.Name, s)
	}

	p, mac := ci.clashesMAC(c)
	if p != nil {
		return fmt.Errorf("another client %q uses the same MAC %q", p.Name, mac)
	}

	return nil
}

// clashesName returns existing persistent client with the same name as c or
// nil.  c must be non-nil.
func (ci *index) clashesName(c *Persistent) (existing *Persistent) {
	existing, ok := ci.findByName(c.Name)
	if !ok {
		return nil
	}

	if existing.UID != c.UID {
		return existing
	}

	return nil

View on GitHub (pinned to b41aefbe51)