fix(config): drop the uptime line from get_config()

`show running-config` is preceded by a header block, and one of its lines
reports the system uptime. That value necessarily differs between any two
reads, so every caller comparing consecutive configs sees a change each
time.

Measured on a GS110TPv3 under NetOrk: 876 of 894 stored config snapshots
marked as changed, one git commit and one config_changed warning per poll,
while every other device at the same installation sat between 2 and 18. The
history was worthless for that switch — a genuine change would have been
invisible among hundreds of uptime diffs.

Only the uptime line is removed. Model, firmware version, serial and MAC are
stable and belong in a config backup; a changed firmware version is exactly
the kind of change worth recording.

netgear_plus is unaffected — its get_config() returns empty strings.

The first read after this lands reports one real change, since the line
disappears from the stored config. That is unavoidable and happens once.

napalm_netgear/netgear_smart.py

@@ -821,6 +821,29 @@ class NetgearSmartDriver(ConfigLifecycleMixin, SwitchDriver):
 
         return interfaces_ip
 
+    _RUNTIME_STATE_LINE = re.compile(r"^\s*!\s*System Up Time:", re.IGNORECASE)
+
+    @classmethod
+    def _strip_runtime_state(cls, config: str) -> str:
+        """Drop lines describing state rather than configuration.
+
+        ``show running-config`` is preceded by a header block, and one of its
+        lines reports the system uptime. That value necessarily differs
+        between any two reads, so a caller diffing consecutive configs sees a
+        change every single time — on a GS110TPv3 that marked 876 of 894
+        stored snapshots as changed and made the history useless.
+
+        Only the uptime line goes. The rest of the header (model, firmware,
+        serial, MAC) is stable, and a changed firmware version is precisely
+        the kind of change a config backup should record.
+        """
+        if not config:
+            return config
+        kept = [
+            ln for ln in config.splitlines(keepends=True) if not cls._RUNTIME_STATE_LINE.match(ln)
+        ]
+        return "".join(kept)
+
     def get_config(
         self,
         retrieve: str = "all",
@@ -836,10 +859,14 @@ class NetgearSmartDriver(ConfigLifecycleMixin, SwitchDriver):
         configs = {"running": "", "startup": "", "candidate": ""}
 
         if retrieve in ("all", "running"):
-            configs["running"] = self._send_paged_command("show running-config")
+            configs["running"] = self._strip_runtime_state(
+                self._send_paged_command("show running-config")
+            )
 
         if retrieve in ("all", "startup"):
-            configs["startup"] = self._send_paged_command("show startup-config")
+            configs["startup"] = self._strip_runtime_state(
+                self._send_paged_command("show startup-config")
+            )
 
         if sanitized:
             configs = napalm_helpers.sanitize_configs(configs, C.CISCO_SANITIZE_FILTERS)

tests/unit/test_driver.py

@@ -587,6 +587,70 @@ exit
 # ---------------------------------------------------------------------------
 
 
+_RUNNING_CONFIG_WITH_HEADER = """\
+show running-config
+SYSTEM CONFIG FILE ::= BEGIN
+! Model: GS110TPv3
+! Firmware Version: 7.1.1.17 [Apr 16 2026 - 17:26:24]
+! MAC Address: 28:94:01:6D:26:7D
+! Serial Number: 7LE4535SA0117
+! System Up Time: 3 days, 9 hours, 22 mins, 45 secs
+!
+vlan database
+vlan 10
+exit
+"""
+
+
+class TestGetConfigDropsRuntimeState:
+    """`show running-config` prefixes a header block that includes uptime.
+
+    Uptime is state, not configuration: it differs between any two reads, so
+    every caller diffing consecutive results sees a change each time. On a
+    real GS110TPv3 that marked 876 of 894 config snapshots as changed and
+    buried any genuine change in the noise.
+    """
+
+    def test_uptime_line_is_dropped(self, driver):
+        driver._send_paged_command = lambda cmd: _RUNNING_CONFIG_WITH_HEADER
+        cfg = driver.get_config(retrieve="running")
+        assert "System Up Time" not in cfg["running"]
+
+    def test_two_reads_with_different_uptimes_are_equal(self, driver):
+        """The whole point: consecutive reads must compare equal."""
+        driver._send_paged_command = lambda cmd: _RUNNING_CONFIG_WITH_HEADER
+        first = driver.get_config(retrieve="running")["running"]
+
+        later = _RUNNING_CONFIG_WITH_HEADER.replace(
+            "3 days, 9 hours, 22 mins, 45 secs", "3 days, 9 hours, 27 mins, 51 secs"
+        )
+        driver._send_paged_command = lambda cmd: later
+        assert driver.get_config(retrieve="running")["running"] == first
+
+    def test_stable_header_lines_are_kept(self, driver):
+        """Firmware, model and serial belong in a config backup."""
+        driver._send_paged_command = lambda cmd: _RUNNING_CONFIG_WITH_HEADER
+        running = driver.get_config(retrieve="running")["running"]
+        assert "! Model: GS110TPv3" in running
+        assert "! Firmware Version: 7.1.1.17 [Apr 16 2026 - 17:26:24]" in running
+        assert "! Serial Number: 7LE4535SA0117" in running
+
+    def test_actual_configuration_survives(self, driver):
+        driver._send_paged_command = lambda cmd: _RUNNING_CONFIG_WITH_HEADER
+        running = driver.get_config(retrieve="running")["running"]
+        assert "vlan 10" in running
+
+    def test_startup_config_is_filtered_too(self, driver):
+        driver._send_paged_command = lambda cmd: _RUNNING_CONFIG_WITH_HEADER
+        cfg = driver.get_config(retrieve="startup")
+        assert "System Up Time" not in cfg["startup"]
+
+    def test_config_without_the_header_is_untouched(self, driver):
+        plain = "vlan database\nvlan 10\nexit\n"
+        driver._send_paged_command = lambda cmd: plain
+        assert driver.get_config(retrieve="running")["running"] == plain
+
+
 class TestGetConfig:
     def test_running_retrieved(self, driver):
         driver._send_paged_command = lambda cmd: "! running config"