1. POSTECH DP&NM Lab 1 Net-SNMP J. Won-Ki Hong Dept. of Computer Science and Engineering POSTECH Tel: 054-279-2244 Email: jwkhong@postech.ac.kr

2. POSTECH DP&NM Lab 2 Contents Net-SNMP Package History of Net-SNMP Applications of Net-SNMP Trap Daemon Architecture of Net-SNMP Agent How to extend SNMP agents with Net-SNMP Net-SNMP URL: www.net-snmp.org

3. POSTECH DP&NM Lab 3 Net-SNMP Package (1/2) Net-SNMP is a suite of applications used to implement SNMPv1, SNMPv2c and SNMPv3 using both IPv4 and IPv6 and includes Command-line applications to: –retrieve information from an SNMP-capable device, either using single requests (snmpget, snmpgetnext), or multiple requests (snmpwalk, snmptable, snmpdelta). –manipulate configuration information on an SNMP-capable device (snmpset). –retrieve a fixed collection of information from an SNMP- capable device (snmpdf, snmpnetstat, snmpstatus). –convert between numerical and textual forms of MIB OIDs, and display MIB content and structure (snmptranslate).

4. POSTECH DP&NM Lab 4 Net-SNMP Package (2/2) A graphical MIB browser (tkmib), using Tk/perl. A daemon application for receiving SNMP notifications (snmptrapd). An extensible agent for responding to SNMP queries for management information (snmpd). A library for developing new SNMP applications, with both C and perl APIs.

5. POSTECH DP&NM Lab 5 History of Net-SNMP Originally based on the Carnegie Mellon University implementation (1992) University of California at Davis SNMP extends CMU-SNMP, calls UCD-SNMP (1995) UCD-SNMP moves to Net-SNMP in April, 2002 (Web sites also moves from www.ucd- snmp.net to www.net-snmp.net) Now, Net-SNMP 5.7 released More detailed history can be found at http://www.net-snmp.org/about/history.html

6. POSTECH DP&NM Lab 6 Applications (1) Common Options  -c community  -v 1 | 2c | 3  -r retries  -t timeout  -p port snmpget [COMMON OPTIONS] [-Cf] OID [OID]... –SNMP application that uses the SNMP GET request to query for information on a network entity –e.g., snmpget -c public localhost system.sysDescr.0 –Result) system.sysDescr.0 = Linux enterflex2.postech.ac.kr …

7. POSTECH DP&NM Lab 7 Applications (2) snmpset [COMMON OPTIONS] OID TYPE VALUE –SNMP application that uses the SNMP SET request to set information on a network entity –Type: i (INTEGER), u (UNSIGNED), s (STRING)… –e.g., snmpset -c private -v 1 localhost system.sysContact.0 s mjchoi@postech.ac.kr snmpwalk [APPLICATION OPTIONS] [COMMON OPTIONS] [OID] –SNMP application that uses SNMP GETNEXT requests to query a network entity –Retrieves lots of data, a part of MIB tree (subtree) at once –e.g., snmpwalk -c public localhost system –Result) system.sysDescr.0 = … system.sysObjectID.0 = … system.sysUpTime.0 = …

8. POSTECH DP&NM Lab 8 Applications (3) snmpstatus [COMMON OPTIONS] –SNMP application that retrieves several important statistics from a network entity. –The IP address of the entity.  sysDescr.0 / sysUpTime.0 /… –e.g., snmpstatus -c public -v 1 localhost –Result) [127.0.0.1]  [Linux enterflex2.postech. ac.kr 2.4.7-10 #1 Thu Sep 6 17 :27:27 EDT 2001 i386 ]… snmptranslate [OPTIONS] OID [OID]... –Application that translates SNMP object identifier values from their symbolic (textual) forms into their numerical forms –e.g., snmptranslate system.sysUpTime.0 –Result).1.3.6.1.2.1.1.3.0

9. POSTECH DP&NM Lab 9 Applications (4) snmptrap [COMMON OPTIONS] [-Ci] enterprise-oid agent generic-trap specific-trap uptime [OID TYPE VALUE] –SNMP application that uses the SNMP TRAP operation to send information to a network manager –Definition) TRAP-TEST-MIB DEFINITIONS ::= BEGIN IMPORTS ucdExperimental FROM UCD-SNMP-MIB; demotraps OBJECT IDENTIFIER ::= { ucdExperimental 990 } demo-trap TRAP-TYPE STATUS current ENTERPRISE demotraps VARIABLES { sysLocation } DESCRIPTION "This is just a demo" ::= 17 END –e.g., snmptrap –v 1 -c public host TRAP-TEST-MIB::demotraps localhost 6 17 '' SNMPv2-MIB::sysLocation.0 s "Just here"

10. POSTECH DP&NM Lab 10 Applications (5) Other SNMP applications: –snmpgetnext: retrieving unknown indexed data. –snmpbulkwalk: uses SNMP GETBULK requests to query a network entity –snmptable: displaying table. –snmpnetstat: symbolically displays the values of various network-related information retrieved from a remote system using the SNMP protocol

11. POSTECH DP&NM Lab 11 Trap Daemon snmptrapd [OPTIONS][LISTENING ADDRESSES] –SNMP application that receives and logs SNMP TRAP –the default is to listen on UDP port 162 –snmptrapd is displayed as follows –Result) 1999-11-12 23:26:07 localhost [127.0.0.1] TRAP-TEST-MIB::demotraps: Enterprise Specific Trap (demo-trap) Uptime: 1 day, 5:34:06 SNMPv2- MIB::sysLocation.0 = "Just here"

12. POSTECH DP&NM Lab 12 Architecture of SNMP Agent SNMPMANAGERSNMPMANAGER SNMPMANAGERSNMPMANAGER Managed System Mgmt. Backend Interface Mgmt. Backend Interface Embedded System Application Embedded System Application SNMP Agent BER Decoder & Encoder BER Decoder & Encoder Message Parser Message Parser Operation Processor Operation Processor Message Generator Message Generator Trap Monitor Trap Monitor Connection Listener Connection Listener Request Response/ Trap

13. POSTECH DP&NM Lab 13 How to Extend (1) 1.Define a private MIB: Example of Cluster MIB

14. POSTECH DP&NM Lab 14 How to Extend (2) 2.Download net-snmp-5.7.1.tar.gz 3.Decompress the file in your home directory command: gtar xvfz net-snmp-5.7.1.tar.gz 4.Compile default SNMP agent –cd net-snmp-5.7.1 –./configure --prefix=“/usr/local/net-snmp” –make –umask 022 –make install

15. POSTECH DP&NM Lab 15 How to Extend (3) 6.Install SNMP perl module for using mib2c cd net-snmp-5.7.1 cd perl perl Makefile.PL -NET-SNMP-CONFIG=“sh../net- snmp-config” -NET-SNMP-IN-SOURCE=true make make test make install

16. POSTECH DP&NM Lab 16 How to Extend (4) 7.Compile the private MIB file using mib2c cd net-snmp-5.7.1 cd local mkdir cluster copy the private mib in the current directory ex) cp ~mjchoi/cluster.my./cluster.my export MIBS=ALL MIBS=./cluster.my mib2c -c mib2c.scalar.conf generalInfo mib2c -c mib2c.scalar.conf currentStatus mib2c -c mib2c.array-user.conf loadBalancer mv generalInfo.* cluster mv currentStatus.* cluster mv loadBalancer.* cluster cp –r cluster../agent/mibgroup/.

17. POSTECH DP&NM Lab 17 How to Extend (5) 8.Code the extension agent Header file: add necessary definitions C file (1) Module definition: the code defining the contents of the MIB e.g., static oid clusterName_oid[] = { 1, 3, 6, 1, 3, 1, 1, 1, 0 }; (2) Module initialization: initialization before they can start providing the necessary information e.g., netsnmp_register_instance(netsnmp_create_handler_registration ("clusterName", do_clusterName, clusterName_oid, OID_LENGTH(clusterName_oid), HANDLER_CAN_RWRITE));

18. POSTECH DP&NM Lab 18 How to Extend (6) 8.Code the extension agent (3) Variable handling: actually handles a request for a particular variable instance e.g., char clusterName[NAME_LEN]; int *var_len; (4) Non-table-based modules: the request handling routine is to retrieve any necessary scalar data e.g., switch (reqinfo->mode) { case MODE_GET: snmp_set_var_typed_value(requests->requestvb, ASN_OCTET_STR, (u_char *) clusterName, var_len); break; … }

19. POSTECH DP&NM Lab 19 How to Extend (7) 8.Code the extension agent (5) Simple tables: process a simple table with limited table index e.g., int serviceTable_handler(netsnmp_mib_handler *handler, netsnmp_handler_registration *reginfo, netsnmp_agent_request_info *reqinfo, netsnmp_request_info *requests) { … switch (reqinfo->mode) { case MODE_GET: switch (table_info->colnum) { case COLUMN_SRINDEX: snmp_set_var_typed_value(var, ASN_INTEGER, …); break; … } … } … }

20. POSTECH DP&NM Lab 20 How to Extend (8) 8.Code the extension agent (6) General tables: process a general table, which the maximum index is not determinable e.g., Init_{Name}_Entry(); // Perform any necessary initialization while (( index = Get_Next_{Name}_Entry() ) != EndMarker ) { construct OID from vp->name and index compare new OID and request if valid { save current data if finished // exact match, or ordered table break; // so don't look at any more entries } … } …

21. POSTECH DP&NM Lab 21 How to Extend (9) 8.Code the extension agent (7) Set-able object: the handling of SNMPSET e.g., switch (reqinfo->mode) { … case MODE_SET_ACTION: // XXX: perform the value change here if ( /* XXX: error? */ ) { netsnmp_set_request_error(reqinfo, requests, “error_msg.”); } break; case MODE_SET_COMMIT: // XXX: delete temporary storage if ( /* XXX: error? */ ) { netsnmp_set_request_error(reqinfo, requests, SNMP_ERR_COMMITFAILED); } break; } …

22. POSTECH DP&NM Lab 22 How to Extend (10) 9.Compile the MIB extension and generate SNMP daemon./configure --with-mib-modules=“cluster/generalInfo, cluster/currentStatus, cluster/loadBalancer” cd agent make./snmpd –c config_file (ex)./snmpd –c /etc/snmp/snmpd.conf –snmpd [OPTIONS] [LISTENING ADDRESSES] –SNMP agent which binds to a port and awaits requests from SNMP management software. –collects the requested information and/or performs the requested operations and returns the information to the sender. –By default, snmpd listens for SNMP requests on UDP port 161.

23. POSTECH DP&NM Lab 23 How to Extend (11) 10.Modify snmpd.conf for SNMP community # First, map the community name # sec.name source community com2sec clusterUser default postech # Second, map the security name into a group name: # groupName securityModel securityName group clusterGroup v1 clusterUser # Third, create a view for us to let the group have rights to: # name incl/excl subtree mask(optional) view mibview included.iso.org.dod.internet # Finally, grant the group read-only access to the systemview view. # group context sec.model sec.level prefix read write notif access clusterGroup "" any noauth exact mibview mibview none

24. POSTECH DP&NM Lab 24 Good-Luck & Have Fun!