# 5.4 Losing a lease

_Peios / Peios technical reference / netd / Dhcpv4_

> How a DHCPv4 lease ends — expiry, a NAK, or the client being stopped — what Address.OnExpiry decides, and when a RELEASE is sent.

## 5.4.1 Lost by the network [*dhcp4-loss.lost]

A lease is **lost** when a Rebinding client reaches the lease's end
(§5.2), or when a NAK arrives while renewing or rebinding (§5.3). The
client forgets the lease and enters Selecting, and netd acts on the
interface's `Address.OnExpiry`:

- **`Drop`** (the default): netd logs `interface <name>: lease lost` and
  forgets the lease. The next reconcile removes the address and the routes
  that came with it. [*dhcp4-loss.drop-removes-the-address]
- **`Keep`**: netd logs `interface <name>: lease lost; keeping the address
  (Address.OnExpiry = Keep)` at warning level and goes on desiring the
  lost lease — its address, gateway and routes — while the client looks
  for a new one. The kept lease is replaced the moment a new one binds.
  [*dhcp4-loss.keep-holds-the-lease]

With `Keep`, the status reply's `lease` describes the client, not the
kept lease: it disappears with the client's lease, while the address
stays on the interface.

`Keep` lasts while the client lasts. A stop (below) forgets the kept lease
as it would any other.

## 5.4.2 Stopped by netd [*dhcp4-loss.stop-releases]

netd stops a client when:

- the interface's outcome changes: another verdict, another profile, or
  any value of its profile edited (§3.3);
- the interface loses carrier (§4.1);
- the profile no longer wants a client (§5.1).

A client in Bound, Renewing or Rebinding sends a RELEASE to its server
first: unicast from the lease address (§5.1, §5.6). After a carrier loss
that RELEASE goes out on a link with no carrier, so the server never sees
it. The client is then discarded, and the interface's lease and
link-local address are forgotten, so the next reconcile removes both
addresses.

A link that disappears from the kernel takes its client with it and
sends nothing.

## 5.4.3 The operator's renew [*dhcp4-loss.operator-renew]

The control request `renew` (§9.2), and so `net renew <interface>`, moves
a client in Bound, Renewing or Rebinding into Renewing at once: a new
transaction id and a unicast REQUEST to the lease's server. The lease is
not released first, and its address stays on the interface throughout.
A client that holds no lease is left as it is, and the request still
answers `ok`.