Routing:
[Gen][CCNA][CCNP Route][CCNP Remote][CCDA][MPLS][EEM][Add][Juniper][ACL][Host]
Switching: [CCNP Switch] [Switch Add] [Intro] [VLANs] [MLS] [STP] [QoS] [Availability] Security: [CCNP Security] [CCNA Security] [CCNP ISCW][PIX] [Adv PIX/ASA] [Net Sec1] [Net Sec2] Wireless: [Wireless] [Wireless Chall] [CCNA Wireless] [Wireless Theory] Voice: [Voice/QoS] [CCNA Voice] [CCVP Gateway] [CCVP Voice] Topics: [Dot1q][Dot1x][BGP][BRI][DHCP][IGRP][IGMP][OSPF][PPP][QoS][RADIUS][RIP][Subnet][SNMP][VLAN] SNMP challengesSNMP (Simple Network Management Protocol) is a well-supported standard which can be used to monitor and control devices. It typically runs of hubs, switches and bridges. Many SNMP devices provides both general network management and device manage-ment through a serial cable, modem, or over the network from a remote computer. It involves a primary management station communicating with different management processes. CCNA Challenges
CCNP Switch
Wireless
PIX/ASA
CCNP ISCW
CCNA Security
CCSP SNRS
TheorySNMP (Simple Network Management Protocol) is a well-supported standard which can be used to monitor and control devices. It typically runs of hubs, switches and bridges. Many SNMP devices provides both general network management and device manage-ment through a serial cable, modem, or over the network from a remote computer. It involves a primary management station communicating with different management processes. Figure 1 shows an outline of an SNMP-based system. A SNMP agent runs SNMP management software. An SNMP server sends commands to the agent which re-sponses back with the results. In Figure 1, the server asks the agent for its routing information and the agent responds with its routing table. These responses can either be polled (the server sends a request for information) or interrupt-driven (where the agent sends its information at given events). A polled system tends to increase network traffic as the agent may not have any updated information (and the server must re-poll for the information). The SNMP (Simple Network Management Protocol) protocol is initially based in the RFC1157 document. It defines a simple protocol which gives network element man-agement information base (MIB). There are two types of MIB: MIB-1 and MIB-2. MIB-1 was defined in 1988 and has 114 table entries, divided into two groups. MIB-2 is a 1990 enhancement which has 171 entries organized into 10 groups (RFC 1213). Most devices are MIB-1 compliant and newer one with both MIB-1 and MIB-2. The database contains entries with four fields:
Figure 1 SNMP architecture SNMP is a very simple protocol but suffers from the fact that it is based on connection-less, unreliable, UDP. The IAB have recommended that the Common Management In-formation Services (CMIS) and Common Management Information Protocol (CMIP) be accepted as standard for future TCP/IP systems. The two main version of SNMP are SNMP Ver1 and SNMP Ver2. SNMP has added security to stop intruders determining network loading or the state of the network. The SNMP architecture is based on a collection of:
The SNMP management information represented by a subset of the ASN.1 language. SNMP models all management agent functions as alterations or inspections of variables. Thus, a protocol entity on a logically remote host interacts with the management agent resident on the network element in order to retrieve (get) or alter (set) variables. SNMP determines the current state of the network by polling for appropriate infor-mation from monitoring center(s). Protocol specificationThe network management protocol operates by inspecting or altering variables on an agent’s MIB (management information base). They communicate by exchanging mes-sages within UDP datagrams. These messages are defined using ASN.1 and are speci-fied in listing 1. They consist of:
The protocol receives messages from:
Listing 1 RFC1157-SNMP DEFINITIONS ::= BEGIN IMPORTS ObjectName, ObjectSyntax, NetworkAddress, IpAddress, TimeTicks FROM RFC1155-SMI; -- top-level message Message ::= SEQUENCE { version -- version-1 for this RFC INTEGER { version-1(0) }, community -- community name OCTET STRING, data -- e.g., PDUs if trivial ANY -- authentication is being used } -- protocol data units PDUs ::= CHOICE { get-request GetRequest-PDU, get-next-request GetNextRequest-PDU, get-response GetResponse-PDU, set-request SetRequest-PDU, trap Trap-PDU } -- the individual PDUs and commonly used -- data types will be defined later END ConfiguringThe SNMP-server command is used to enable SNMP monitoring, such as: 1. Go into the privileged mode by typing enable. 2. Configure the device using by typing config t. 3. The snmp-server community command is used to initialise SNMP. For example to define the read-only string to public: (config)# snmp-server community public RO or for read-write access use RW instead of RO. The community access string (in this case, public) acts as a password for the access to the SNMP information. To setup the SNMP contact: (config)# snmp-server contact fred smith and to set the location: (config)# snmp-server location room c27 To enable SNMP traps so that all the data is monitored: (config)# snmp-server enable traps and to send these traps to a remote host (to www.myhost.com): (config)# snmp-server host www.myhost.com public 4. Go back to the user executive mode with the command exit. 5. Show the main system configuration with show running-config. 6. To show SNMP event values: # show management event and to determine the status of the SNMP communications: # show snmp and to display the SNMP engine and remote engines: # show snmp engine and to display the SNMP group: # show snmp group SNMP uses an MIB database to store its values. To display its contents: # show snmp mib To show the currently pending SNMP requests: # show snmp pending To show the SNMP sessions: # show snmp sessions 7. Show the main system configuration with show running-config. |