Re: NetConf Yang for DHCP Operations returning empty string.

kn2022 · ‎06-19-2023

Hi,

I am trying to use the operations data to query for the dhcp lease information.
Below is the snippet of netconf-yang and the code.

filter = """
<filter xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <native xmlns="http://cisco.com/ns/yang/Cisco-IOS-XE-dhcp-oper">
  <dhcp-oper-data>
     <dhcpv4-server-oper>
     </dhcpv4-server-oper>
  </dhcp-oper-data>
  </native>
</filter>
"""
# Establish a NETCONF session with the device
with manager.connect(host="X.X.X.X", port=XXX, username="XXX", password="XXXXXXXX", hostkey_verify=False, device_params={'name':'csr'}) as m:
    # Retrieve the DHCP pool configuration
    response = m.get("running", filter)
    # Print the XML response
    dom = xml.dom.minidom.parseString(response.xml)
    pretty_xml_as_string = dom.toprettyxml()
    print(pretty_xml_as_string)

This returns error as below

[knanda@stratos-rochester-directlink-vsi code]$ python dhcp_stats.py
Traceback (most recent call last):
  File "X/code/dhcp_stats.py", line 82, in <module>
    response = m.get("running", filter)
  File "X/.local/lib/python3.9/site-packages/ncclient/manager.py", line 246, in execute
    return cls(self._session,
  File "X/.local/lib/python3.9/site-packages/ncclient/operations/retrieve.py", line 83, in request                                                                                                        
    node.append(util.build_filter(filter))
  File "X/.local/lib/python3.9/site-packages/ncclient/operations/util.py", line 74, in build_filter                                                                                                       
    rep = validated_element(spec, ("filter", qualify("filter"),
  File "X/.local/lib/python3.9/site-packages/ncclient/xml_.py", line 150, in validated_element
    ele = to_ele(x)
  File "X/.local/lib/python3.9/site-packages/ncclient/xml_.py", line 129, in to_ele
    return x if etree.iselement(x) else etree.fromstring(x.encode('UTF-8'), parser=_get_parser(huge_tree))
  File "src/lxml/etree.pyx", line 3257, in lxml.etree.fromstring
  File "src/lxml/parser.pxi", line 1916, in lxml.etree._parseMemoryDocument
  File "src/lxml/parser.pxi", line 1803, in lxml.etree._parseDoc
  File "src/lxml/parser.pxi", line 1144, in lxml.etree._BaseParser._parseDoc
  File "src/lxml/parser.pxi", line 618, in lxml.etree._ParserContext._handleParseResultDoc
  File "src/lxml/parser.pxi", line 728, in lxml.etree._handleParseResult
  File "src/lxml/parser.pxi", line 657, in lxml.etree._raiseParseError
  File "<string>", line 1
lxml.etree.XMLSyntaxError: Start tag expected, '<' not found, line 1, column 1

Mohamed Alhenawy · ‎06-19-2023

hi @kn2022

Verify that the YANG model for the DHCP operational data is supported by your device's software version. Some YANG models may not be available or supported on certain device versions, and attempting to retrieve data that is not supported can result in parsing errors.

kn2022 · ‎06-19-2023

Thanks. I think it does support it. I checked on capabilities and I find these two being listed.

**************************************************
http://cisco.com/ns/yang/Cisco-IOS-XE-dhcp?module=Cisco-IOS-XE-dhcp&revision=2020-07-04
**************************************************
http://cisco.com/ns/yang/Cisco-IOS-XE-dhcp-oper?module=Cisco-IOS-XE-dhcp-oper&revision=2019-05-01
**************************************************

when I run the following code

# Establish a NETCONF session with the device
with manager.connect(**device) as m:
    for capability in m.server_capabilities:
        print('*'* 50)
        print(capability)