SNMP Fundamentals PDF

1 v1.2 SNMP Fundamentals 2 v1.2 Table of Content What is SNMP (Simple Network Management Protocol)? SNMP Components SNMP Protocol Commands SNMP Version SNMP Communities SNMP – Packet Capture SNMP Configuration Examples 3...

1 v1.2 SNMP Fundamentals 2 v1.2 Table of Content What is SNMP (Simple Network Management Protocol)? SNMP Components SNMP Protocol Commands SNMP Version SNMP Communities SNMP – Packet Capture SNMP Configuration Examples 3 v1.2 What is SNMP Simple Network Management Protocol Application layer protocol used to manage and monitor network devices and their functions What SNMP Does – Detect issues and fault early – Monitor device throughput – Remote configuration and control SNMP uses the User Datagram Protocol (UDP) as the transport protocol rfc1157 4 v1.2 SNMP Components SNMP Manager SNMP Agent Management Information Base (MIB) Managed Devices 5 v1.2 SNMP Components – SNMP Manager SNMP Manager – Polls devices to obtain information and alerts – Typically a central software application – Option for email/SMS alerts to administrators – Poling happens over UDP port 161 (default) 6 v1.2 SNMP Components – SNMP Agent SNMP Agent – Process running on a monitored device – Information sent as a response to poling – Unsolicited message (traps) can also be sent – Information sent over UDP port 162 (default) Trap sent to NMS NMS Query sent to agent Agent Router Response to query sent from the agent to the NMS Relationship between an NMS and an agent 7 v1.2 SNMP Components – MIB Management Information Base (MIB) – Collection of definitions which define the properties of the managed object – Each managed device keeps a database of values for each of the definitions written in the MIB – The MIB is a hierarchical structure that forms a tree and the MIB contains object identifiers or OIDs – An OID is an object identifier value, typically an address used to identify a particular device and its status 8 v1.2 SNMP Components – OID in MIB SNMP-enabled network devices maintains database of system status, availability and performance information as objects, identified by OIDs For example, OID for system description (sysDescr) is.1.3.6.1.2.1.1.1.0. or.iso.org.dod.internet.mgmt. mib-2.system.sysDescr.0 9 v1.2 SNMP Components – MIB An agent may implement many MIBs, but all agents implement a particular MIB called MIB-II The main goal of MIB-II (RFC 1213) is to provide general TCP/IP management information – interface speeds, MTU, octets sent, octets received, system location, system contact, etc There are many other draft and proposed standards – Interface Type MIB (RFC 2115) – BGP Version 4 MIB (RFC 1657) – DNS Server MIB (RFC 1611) rfc1213 Vendor also defines its own MIB (proprietary MIB) 10 v1.2 SNMP Components – Standard MIB Standard MIBs https://bestmonitoringtools.com/mibdb/mibdb_search.php?mib=BGP4-MIB https://bestmonitoringtools.com/mibdb/mibdb_search.php?mib=IF-MIB 11 v1.2 SNMP Components – Proprietary MIB Cisco Feature Navigator – https://cfnng.cisco.com/mibs Juniper SNMP MIB Explorer – https://apps.juniper.net/mib-explorer 12 v1.2 SNMP Components – Managed Devices Managed Devices – Controlled by an agent – SNMP information source 13 v1.2 SNMP Protocol Commands Messaging Description Get A Get message is sent by a manager to an agent to request the value of a specific OID GetNext A GetNext message allows a manager to request the next sequential object in the MIB Set A Set message is sent by a manager to an agent in order to change the value held by a variable on the agent GetBulk This manager to agent request functions as if multiple GetNext requests were made Response This message, sent by an agent, is used to send any requested information back to the manager Trap Traps are asynchronous notifications in that they are unsolicited by the manager receiving them Inform Manager sends an Inform message back to the agent as acknowledgement 14 v1.2 SNMP Message Exchange Mechanism 15 v1.2 SNMP Version Three significant versions of SNMP – SNMPv1 Defined in RFC 1157 No inform-request option Uses community string for security Community string is passed in clear text – SNMPv2 Referred to as SNMP v2c Addition of the inform-request option Community string used for authentication 64-bits counters – SNMPv3 Most current version Addition of unique EngineIDs for SNMP devise Adds authentication based on MD5 or SHA Adds encryption through DES, 3DES or AES 16 v1.2 SNMP Communities – SNMP v1 and v2 SNMPv1 and SNMPv2 use communities to establish trust between managers and agents An agent is configured with three community names: – read-only – read-write and – trap The community names are essentially passwords Typically public for the read-only community and private for the read-write community 17 v1.2 SNMPv3 Security Levels Ensure confidentiality, authentication and access control Authentication Encryption Username Password NoAuthNoPriv No No Yes No AuthNoPriv Yes No Yes Yes AuthPriv Yes Yes Yes Yes 18 v1.2 SNMP – Packet Capture snmpwalk -v 2c -c {community} 192.168.99.252 19 v1.2 Configuration Example – SNMPv1 and v2 Create a community with write access router(config)# access-list 66 permit 192.168.11.5 router(config)# snmp-server community example1rw rw 66 Create a community with read-only access router(config)# access-list 67 permit 192.168.16.1 router(config)# snmp-server community example2ro ro 67 20 v1.2 Configuration Example – SNMPv3 Create a community with write access router(config)# snmp-server view viewAPNIC iso included router(config)# snmp-server group grpAPNIC v3 priv read viewAPNIC router(config)# snmp-server user apnic grpAPNIC v3 auth sha AUTHPASS priv aes 128 PRIVPASS 21 v1.2 SNMP Fundamentals Module 2: LibreNMS 22 v1.2 LibreNMS A Fully Featured Network Monitoring Tool for Linux LibreNMS is an open source, powerful and feature-rich auto- discovering PHP based network monitoring system which uses the SNMP protocol It supports a broad range of operating systems including Linux, FreeBSD, as well as network devices including Cisco, Juniper, Brocade, Foundry, HP and many more 23 v1.2 LibreNMS - Features Some major features of LibreNMS – It auto-discovers a whole network using these protocols: CDP, FDP, LLDP, OSPF, BGP, SNMP and ARP – Supports a Unix agent – Supports horizontal scaling to expand with your network – Supports a highly flexible and customizable alerting system; sends notifications through email, irc, slack and more – Supports an API for managing, graphing and retrieving data from your system – Offers a traffic billing system – Supports integration with NfSen, collectd, SmokePing, RANCID and Oxidized – Supports multiple authentication methods such as MySQL, HTTP, LDAP, Radius and Active Directory 24 v1.2 LibreNMS vs Observium LibreNMS is a fork of Observium How LibreNMS will be different from Observium: – Inclusive community, where it's OK to ask stupid questions, and OK to ask for things that aren't on the roadmap. – Development decisions will be community-driven. Want to make software that fulfils its users' needs – There are no plans for a paid version – There are no current plans for paid support, but this may be added later if there is sufficient demand 25 v1.2 LibreNMS - Architecture LibreNMS has following components: – Web/API Layer: This is typically Apache but we have setup guides for both Nginx and Lighttpd – RRD (Time Series Data store): Central storage should be provided so all RRD files can be read from and written to in one location – Database: MySQL / MariaDB – Poller/Discovery: To gather information and discover network. Cron based polling is the common setup All these components may only be installed on one server For scaling LibreNMS; distributed polling has been used. 26 v1.2 LibreNMS - Metrics LibreNMS supports wide range of metrics which includes: – Memory, Processor and Storage – Temperature, Voltage and Fan speed – Interface traffic and statistics – OS/Distribution detection – Routing information (BGP and OSPF) – Wide range of application monitoring (Apache, Asterisk, BIND, FreeRADIUS, MySQL, NTP, NGINX, Postfix, Squid, Unbound etc.) https://docs.librenms.org/Extensions/Applications/ – IPv4, IPv6, TCP and UDP statistics 27 v1.2 LibreNMS - Metric Storage By default we ship all metrics to RRD files, either directly or via RRDCached On top of this we can ship metrics to – Graphite – InfluxDB – OpenTSDB – Prometheus At present these backends can’t be used to display graphs within LibreNMS and need to use something like Grafana 28 v1.2 LibreNMS - Auto Discovery LibreNMS is based on SNMP Support following methods for auto discovery: – ARP – XDP (FDP, CDP, LLDP) – OSPF – BGP – SNMP Scan 29 v1.2 LibreNMS - 3 rd Party Integration LibreNMS integration – Graylog -> https://docs.librenms.org/Extensions/Graylog/ – Nagios -> https://docs.librenms.org/Extensions/Services/ – NFSen -> https://docs.librenms.org/Extensions/NFSen/ – Oxdizied -> https://docs.librenms.org/Extensions/Oxidized/ – Smokeping -> https://docs.librenms.org/Extensions/Smokeping/ 30 v1.2 LibreNMS - Demo Demo URL: https://demo.librenms.org/ – Username: demo – Password: demouser 31 v1.2 SNMP Fundamentals Module 3: LAB 32 v1.2 Labs Please follow the lab modules for – Lab 1: Net-SNMP – Lab 2: LibreNMS 33 v1.2 Thank You! 34 v1.2