diff --git a/genua/agent_based/genua_extend.py b/genua/agent_based/genua_extend.py
new file mode 100644
index 0000000..908364a
--- /dev/null
+++ b/genua/agent_based/genua_extend.py
@@ -0,0 +1,173 @@
+#!/usr/bin/env python3
+
+"""checkmk plugin for GENUA-EXTEND-MIB"""
+
+from cmk.agent_based.v2 import (
+    SimpleSNMPSection,
+    SNMPTree,
+    StringTable,
+    State,
+    CheckPlugin,
+    DiscoveryResult,
+    CheckResult,
+    Service,
+    Result,
+    check_levels,
+    all_of,
+    exists,
+)
+
+from cmk.plugins.lib.genua import DETECT_GENUA
+
+import re
+
+Section = dict[str, dict[str, str]]
+
+
+def parse_genua_extend(string_table: StringTable) -> Section:
+    parsed = {}
+    for line in string_table:
+        extendName, extendDescription, extendStatus, extendPerformancedata = line
+        extendPerformancedata = {
+            name: val
+            for name, val in [
+                a.split("=") for a in extendPerformancedata.split(" ") if "=" in a
+            ]
+        }
+        sub_parsed = {
+            "extendName": extendName,
+            "extendDescription": extendDescription,
+            "extendStatus": int(extendStatus),
+            "extendPerformancedata": extendPerformancedata,
+        }
+        parsed[extendName] = sub_parsed
+    return parsed
+
+
+snmp_section_genua_extend = SimpleSNMPSection(
+    name="genua_extend",
+    detect=all_of(
+        DETECT_GENUA,
+        exists(".1.3.6.1.4.1.3717.66.1.1.*"),  # genuaExtend
+    ),
+    fetch=SNMPTree(
+        base=".1.3.6.1.4.1.3717.66.1.1",  # GENUA-EXTEND-MIB::extendTable
+        oids=[
+            "1",  # extendName
+            "2",  # extendDescription
+            "3",  # extendStatus
+            "4",  # extendPerformancedata
+        ],
+    ),
+    parse_function=parse_genua_extend,
+)
+
+
+def discover_genua_extend(section: Section) -> DiscoveryResult:
+    for check in section.keys():
+        yield Service(
+            item=check,
+        )
+
+
+# Helpers
+
+
+def float_ignore_uom(value: str) -> float:
+    """16MB -> 16.0"""
+    while value:
+        try:
+            return float(value)
+        except ValueError:
+            value = value[:-1]
+    return 0.0
+
+
+def uom_from_value(value: str) -> str:
+    """16.2MB -> MB"""
+    m = re.match(r"[0-9.]* ?(.*)", value)
+    return m.group(1) if m else None
+
+
+def render_value_func(uom):
+    """Render function with supplied UOM"""
+
+    def render_value(value):
+        int_value = int(value)
+        if value == int_value:
+            value = int_value
+        return f"{value} {uom}"
+
+    return render_value
+
+
+def parse_thresholds(t):
+    """Parse simple Nagios-style thresholds
+    '10', '10:' or '10:20' are supported, but not @, ~"""
+    if ":" in t:
+        upper, _, lower = t.partition(":")
+        upper = float_or_none(upper)
+        lower = float_or_none(lower)
+        return lower, upper
+    return float_or_none(t), None
+
+
+def float_or_none(string):
+    try:
+        f = float(string)
+        return f
+    except ValueError:
+        return None
+
+
+def check_genua_extend(item: str, params: dict, section: Section) -> CheckResult:
+    pe = section.get(item, {})
+    statuscode = pe.get("extendStatus", 99)
+    code2state = {0: State.OK, 1: State.WARN, 2: State.CRIT, 3: State.UNKNOWN}
+
+    if statuscode in range(0, 4):
+        yield Result(
+            state=code2state[statuscode],
+            summary=pe.get("extendDescription", "No Description"),
+        )
+    else:
+        desc = pe.get("extendDescription", "No SNMP data")
+        yield Result(state=State.UNKNOWN, summary=desc)
+    extendPerformancedata = pe.get("extendPerformancedata", {})
+    for name, value in extendPerformancedata.items():
+        split_v = value.split(";")
+        while len(split_v) <= 5:
+            split_v.append("")
+        value, warn, crit, min_bound, max_bound = split_v[0:5]
+        check_params = {}
+
+        min_bound = float_or_none(min_bound)
+        max_bound = float_or_none(max_bound)
+        crit_upper, crit_lower = parse_thresholds(crit)
+        warn_upper, warn_lower = parse_thresholds(warn)
+
+        if min_bound or max_bound:
+            check_params["boundaries"] = (min_bound, max_bound)
+        if warn_upper and crit_upper:
+            check_params["levels_upper"] = ("fixed", (crit_upper, warn_upper))
+        if warn_lower and crit_lower:
+            check_params["levels_lower"] = ("fixed", (crit_lower, warn_lower))
+        uom = uom_from_value(value)
+        value = float_ignore_uom(value)
+        if uom:
+            check_params["render_func"] = render_value_func(uom)
+
+        yield from check_levels(
+            value, metric_name=name, label=name, notice_only=True, **check_params
+        )
+
+
+check_plugin_genua_extend = CheckPlugin(
+    name="genua_extend",
+    service_name="Extend %s",
+    sections=["genua_extend"],
+    discovery_function=discover_genua_extend,
+    check_function=check_genua_extend,
+    check_ruleset_name="genua_extend",
+    check_default_parameters={},
+)
diff --git a/genua/checkman/genua_extend b/genua/checkman/genua_extend
new file mode 100644
index 0000000..24ed7c7
--- /dev/null
+++ b/genua/checkman/genua_extend
@@ -0,0 +1,15 @@
+title: genua: Extend
+agents: snmp
+catalog: hw/network/genua
+license: GPLv2
+distribution: check_mk
+description:
+ This check shows custom check data created by customer specific scripts on
+ genua appliances. The format is described in GENUA-EXTEND-MIB.
+
+ The check supports the OID table under ".1.3.6.1.4.1.3717.66.1.1"
+
+discovery:
+ A service is created if
+ - the device is recognized as a genua device
+ - the OID table under ".1.3.6.1.4.1.3717.66.1.1.*" exists