Python | the broadcast

Today I’ll show how retrieve additional details from already discoverd QoS-Counters. They are mostly descriptive, for human eyes.
The „Traffic-Direction“-Attribute might be relevant since in most cases only outbound drop-counters might be interesting, so the discovered list of OIDs could get filtered to process only those outbound OIDs.

Refresh: Retrieve all „QoS Packet-Counters“

>>> cbqos = session.walk('1.3.6.1.4.1.9.9.166.1.15.1.1.2')
>>> print cbqos
[<SNMPVariable value='9' (oid='enterprises.9.9.166.1.15.1.1.2.18.65536', oid_index='', snmp_type='COUNTER')>,
<SNMPVariable value='0' (oid='enterprises.9.9.166.1.15.1.1.2.18.131072', oid_index='', snmp_type='COUNTER')>,
<SNMPVariable value='1035' (oid='enterprises.9.9.166.1.15.1.1.2.18.196608', oid_index='', snmp_type='COUNTER')>,
<SNMPVariable value='0' (oid='enterprises.9.9.166.1.15.1.1.2.34.65536', oid_index='', snmp_type='COUNTER')>,
<SNMPVariable value='0' (oid='enterprises.9.9.166.1.15.1.1.2.34.131072', oid_index='', snmp_type='COUNTER')>,
<SNMPVariable value='0' (oid='enterprises.9.9.166.1.15.1.1.2.34.196608', oid_index='', snmp_type='COUNTER')>]

There are two Policy-Objects #P:

Policy #18
Policy #34

Both Policy-Objects contain three Traffic-Classes #Q:

Class #65535
Class #131072
Class #196608

Attributes of a bound Policy #P

Each Policy has at least two attributes:

Interface-Type of the Policy (5 : CoPP)

1:mainInterface
2:subInterface
3:frDLCI
4:atmPVC
5:controlPlane
6:vlanPort
7:evc

Traffic-Direction

1:input
2:output

Interface bound to

Get the type of a Policy = „cbQosServicePolicyEntry.2.#P“ = „1.3.6.1.4.1.9.9.166.1.1.1.1.2.#P“

both are type „1“ = Main-Interface

>>> print session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.2.18")
<SNMPVariable value='1' (oid='enterprises.9.9.166.1.1.1.1.2.18', oid_index='', snmp_type='INTEGER')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.2.34")
<SNMPVariable value='1' (oid='enterprises.9.9.166.1.1.1.1.2.34', oid_index='', snmp_type='INTEGER')>

Direction = „cbQosServicePolicyEntry.3.#P“ = „1.3.6.1.4.1.9.9.166.1.1.1.1.3.#P“

both are direction „2“ = Output

>>> print session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.3.18")
<SNMPVariable value='2' (oid='enterprises.9.9.166.1.1.1.1.3.18', oid_index='', snmp_type='INTEGER')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.3.34")
<SNMPVariable value='2' (oid='enterprises.9.9.166.1.1.1.1.3.34', oid_index='', snmp_type='INTEGER')>

Interface-ID = „cbQosServicePolicyEntry.4.#P“ = „1.3.6.1.4.1.9.9.166.1.1.1.1.4.#P“ (cbQosIfIndex)

Policy#18 is bound to Interface #1
Policy#34 is bound to Interface #2

>>> print session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.4.18")
<SNMPVariable value='1' (oid='enterprises.9.9.166.1.1.1.1.4.18', oid_index='', snmp_type='INTEGER')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.4.34")
<SNMPVariable value='2' (oid='enterprises.9.9.166.1.1.1.1.4.34', oid_index='', snmp_type='INTEGER')>

Interface-NAME = „1.3.6.1.2.1.2.2.1.2.#IFID“ (ifDescr)

Interface#1 is named „GigabitEthernet1“
Interface#2 is named „GigabitEthernet2“

>>> print session.get("1.3.6.1.2.1.2.2.1.2.1")
<SNMPVariable value='GigabitEthernet1' (oid='ifDescr', oid_index='1', snmp_type='OCTETSTR')>
>>> print session.get("1.3.6.1.2.1.2.2.1.2.2")
<SNMPVariable value='GigabitEthernet2' (oid='ifDescr', oid_index='2', snmp_type='OCTETSTR')>

Attributes of the Traffic-Classes #Q in Policy #P

Each Traffic-Class has (beyond of all counters) the attribute:

Name

Class-ID = „1.3.6.1.4.1.9.9.166.1.5.1.1.2.#P.#Q“ (cbQosConfigIndex)

Class #65535 in Policy #18 has ID #309479785
Class #131072 in Policy #18 has ID #342719994
Class #196608 in Policy #18 has ID #1593
Class #65535 in Policy #34 has ID #309479785
Class #131072 in Policy #34 has ID #342719994
Class #196608 in Policy #34 has ID #1593

since the Class-IDs are the same, it seems to be one and the same policy-map bound to two interfaces

>>> print session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2.18.65536")
<SNMPVariable value='309479785' (oid='enterprises.9.9.166.1.5.1.1.2.18.65536', oid_index='', snmp_type='GAUGE')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2.18.131072")
<SNMPVariable value='342719994' (oid='enterprises.9.9.166.1.5.1.1.2.18.131072', oid_index='', snmp_type='GAUGE')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2.18.196608")
<SNMPVariable value='1593' (oid='enterprises.9.9.166.1.5.1.1.2.18.196608', oid_index='', snmp_type='GAUGE')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2.34.196608")
<SNMPVariable value='1593' (oid='enterprises.9.9.166.1.5.1.1.2.34.196608', oid_index='', snmp_type='GAUGE')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2.34.65536")
<SNMPVariable value='309479785' (oid='enterprises.9.9.166.1.5.1.1.2.34.65536', oid_index='', snmp_type='GAUGE')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2.34.131072")
<SNMPVariable value='342719994' (oid='enterprises.9.9.166.1.5.1.1.2.34.131072', oid_index='', snmp_type='GAUGE')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2.34.196608")
<SNMPVariable value='1593' (oid='enterprises.9.9.166.1.5.1.1.2.34.196608', oid_index='', snmp_type='GAUGE')>
>>>

Class-NAME = „1.3.6.1.4.1.9.9.166.1.7.1.1.1.#CLASS-ID“ (cbQosCMName)

Class #309479785 has the name „CM_VOIP_RTP“
Class #342719994 has the name „CM_VOIP_CTRL“
Class #1593 has the name „class-default“

>>> print session.get("1.3.6.1.4.1.9.9.166.1.7.1.1.1.309479785")
<SNMPVariable value='CM_VOIP_RTP' (oid='enterprises.9.9.166.1.7.1.1.1.309479785', oid_index='', snmp_type='OCTETSTR')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.7.1.1.1.342719994")
<SNMPVariable value='CM_VOIP_CTRL' (oid='enterprises.9.9.166.1.7.1.1.1.342719994', oid_index='', snmp_type='OCTETSTR')>
>>> print session.get("1.3.6.1.4.1.9.9.166.1.7.1.1.1.1593")
<SNMPVariable value='class-default' (oid='enterprises.9.9.166.1.7.1.1.1.1593', oid_index='', snmp_type='OCTETSTR')>

Put it all together
Fetch the list of all „Packet-Counter“-OIDs.

Get the Queue/Class-Details and the Packet-Counter per Class.

session = Session(hostname='192.168.2.72', community='READ', version=2)

cbqos = session.walk('1.3.6.1.4.1.9.9.166.1.15.1.1.2')

ifType=["","mainInterface","subInterface","frDLCI","atmPVC","controlPlane","vlanPort","evc"]
ifDir=["","input","output"]

for i in cbqos:
  oidList=i.oid.split(".")
  q=oidList.pop()
  p=oidList.pop()

  ifTypeID=int(session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.2."+p).value)
  ifDirID=int(session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.3."+p).value)
  ifID=session.get("1.3.6.1.4.1.9.9.166.1.1.1.1.4."+p).value
  ifName=session.get("1.3.6.1.2.1.2.2.1.2."+ifID).value
  classID=session.get("1.3.6.1.4.1.9.9.166.1.5.1.1.2."+p+"."+q).value
  className=session.get("1.3.6.1.4.1.9.9.166.1.7.1.1.1."+classID).value
  pktCounter=session.get(i.oid).value
  print ifName+"("+ifType[ifTypeID]+")"+ifDir[ifDirID],className,pktCounter+" Packets"

Example Output:

GigabitEthernet1(mainInterface)output CM_VOIP_RTP 9 Packets
GigabitEthernet1(mainInterface)output CM_VOIP_CTRL 0 Packets
GigabitEthernet1(mainInterface)output class-default 1716 Packets
GigabitEthernet2(mainInterface)output CM_VOIP_RTP 0 Packets
GigabitEthernet2(mainInterface)output CM_VOIP_CTRL 0 Packets
GigabitEthernet2(mainInterface)output class-default 0 Packets

Background: I plan to design and implement a controller-based QoS-Solution with distributed control-plane using SNMP and RMON.

How to send SNMP-Requests in Python?

Why Python? It’s an arbitrary decision, every programming language might be sufficient. For the moment, I prefer Python for new projects.

I decided to try Easy-SNMP, since good performance and a nice python-programming-interface seem to be killer-features for me.

EasySNMP homepage
EasySNMP documentation

A development environment

clone an ubuntu-server VM

https://allones.de/2017/11/17/linux-quick-and-…ab-vm-deployment/

install net-snmp

sudo apt-get install libsnmp-dev snmp-mibs-downloader

install gcc, python

sudo apt-get install gcc python-dev python-pip

install EasySNMP

pip install easysnmp

Enable SNMP on a Router
Never ever enable SNMP-Access for everybody, don’t even think about it.
Use an ACL permitting only the SNMP-Manager.

ip access-list standard ACL_SNMP
    permit host 192.168.2.89

snmp-server community READ ro ACL_SNMP

! just as an example System-Variable
snmp-server location allones.de

Access the Router via SNMP
The router’s LAN-IP is 192.168.2.72.

I like the „Session“-Interface:

user@snmp-server:~$ python
Type "help", "copyright", "credits" or "license" for more information.
>>>
>>> from easysnmp import Session
>>>
>>> session = Session(hostname='192.168.2.72', community='READ', version=2)

Be aware to poll the Object-Instance, not the Object-Tree-Position.
Wrong

>>> location = session.get('sysLocation')
>>> print location
<SNMPVariable value='NOSUCHINSTANCE' (oid='sysLocation', oid_index='', snmp_type='NOSUCHINSTANCE')>

Correct: Specify an Instance-ID

>>>
>>> location = session.get('sysLocation.0')
>>> print location
<SNMPVariable value='allones.de' (oid='sysLocation', oid_index='0', snmp_type='OCTETSTR')>

Works!

How to access the return-value?
How to verify the Datatype?

I’ve been using the Cisco-developed TCL-Interface for years, the „snmp_getone“-command there, where you had to parse the return-value (a string similar to the „location“-Variable above) applying regular expressions… Weird.

Just remembering the blog post, which motivated me to learn TCL… Ten years old, how time flies!
Read: „SNMP with TCL“ by Ivan Pepelnjak

Might this be easy with EasySNMP?

>>> print location.value
allones.de

>>> print location.oid
sysLocation
>>> print location.oid_index
0

>>> print location.snmp_type
OCTETSTR

Isn’t EasySNMP beautiful!? 🙂

Schlagwort: Python

Getting Details of a Traffic Class from the SNMP-MIB

Linux: SNMP with Python