Hot answers tagged

39

There seems to be a little confusion... you are asking about ARP tables, and you're using OID .1.3.6.1.2.1.17.4.3.1.2; however, that OID actually is for the mac-address table in the switch. I am assuming you know how to login to your Ubuntu server, and that NET-SNMP is installed... please let me know if you need pointers for doing this (see this question for ...


15

SNMPv2u is a user-based security model, as specified in RFC 1909 and RFC 1910. SNMPv2c is a common community-based security model. SNMP 2u offers per-user authentication, similar to SNMPv3. SNMPv2u never really took off in the wild; anyone who wants per-user authentication uses SNMPv3. For more details (and there are a lot), consider this article in the ...


12

I think that you have another switch or hub connected to port 24 of your 2960, and there are 4 hosts connected to that switch/hub.


10

Private MIBs are usually vendor specific. They contain additional information for their specific equiment which cannot be provided through RFC-defined MIBs. This way the vendor can provide more information. To answer your second question: sometimes vendors provide both: the RFC-defined MIB contains all that can be contained there (so most software using ...


10

Try adding the counter command under the SVI (see here for more information, specifically the "Understanding L3 interface counters" section). For instance: Cisco#config t Cisco(config)#interface vlan 100 Cisco(config-if)#counter ? ipv4 Enable IPv4 statistic counters ipv6 Enable IPv6 statistic counters <cr> Cisco(config-if)#counter ...


9

I think your issue is coming from a simple misconception of how SNMP data (OIDs) is structured, and how snmpwalk, snmpget, and snmpgetnext interact with it. SNMP organizes the OIDs into related nested trees (or tables), the MIBs define those trees and the OIDs in them. It's important to understand how snmpget and snmpgetnext works before getting into ...


9

The MIB is the entire catalog of OIDs (for a particular device). An OID is a specific reference to an individual item within the MIB. An analogy: The MIB is like the phone book for my city. The OID is like my name in the phone book.


8

I don't believe there is a way to directly poll the results of the OR via SNMP, but you can certainly poll for the IP SLA results and calculate it yourself. Using the CISCO-RTTMON-MIB (1.3.6.1.4.1.9.9.42), you can check the timeout value of your reachability checks, take the true/false value it returns and do the OR in whatever scripting language you're ...


8

my own solution comes out in the form of iso.3.6.1.2.1.17.4.3.1.2.0.20.42.49.139.235 25 ... do the other numbers represent a MAC address and if so, why are they different from the give solution? First, I apologize for not including this dependency... The MIB tables you're polling are indexed by a value. In this case, you're polling ...


8

Why can't I see MAC addresses of the attached PCs on polling the OID for the above switch? When you poll 1.3.6.1.2.1.4.22.1.2, you're polling ipNetToMediaPhysAddress, which is the ARP table of the switch. Pure Layer2 switches do not have a large ARP table because they are merely switching instead of routing. Switching does not require an ARP table. ...


8

Interfaces/IP Addressing: If you're looking to poll a device's IP address, subnet mask and corresponding interface you can use the following OIDs from the IP-MIB and IF-MIB MIBs: .1.3.6.1.2.1.4.20.1.1 - The IP address can be found at this OID ~]$ snmptranslate .1.3.6.1.2.1.4.20.1.1 IP-MIB::ipAdEntAddr ~]$ snmpwalk -v2c -c cisco 10.30.46.1 .1.3.6.1.2.1.4....


7

Could someone please tell me the community string indexing for switches other than Cisco? Edit: This is how to poll Q-BRIDGE-MIB for mac-addresses from the only non-Cisco I have, a DLink DGS-3200. I'm not using [community@vlan] for non-Cisco switches. You're correct that this indexing only applies to Ciscos. I expect any non-Cisco switch, which supports ...


7

Have you taken a look at the ipRouteTable OID in the RFC1213-MIB? (OID number 1.3.6.1.2.1.4.21) I utilize this to pull the routing table out of several devices. It is referenced by RFC 1213 which, on page 33, gives the following information: -- The IP routing table contains an entry for each route -- presently known to this entity. ...


7

Private MIBs refer to MIBs associated with a specific Private Enterprise Number which starts at the following prefix: iso.org.dod.internet.private.enterprise (1.3.6.1.4.1) These numbers are assigned by IANA and are a namespace for an organization to store their custom OIDs/MIBs. You can see the full list of PENs here. For example, all of Cicso's proprietary ...


6

First, do 'Octets' in ifInOctets and ifOutOctets actually refer to packets? Can someone explain in detail? ifInOctets and ifOutOctets refer to bytes received and transmitted (respectively) by the interfaces indexed to ifIndex / ifName; ifInOctets and ifOutOctets use 32 bit wide values. Unless you're polling interfaces at 100Mbps or lower, I'd strongly ...


6

You probably want to be polling the CAM/MAC tables, that would have the MAC address of any devices send any traffic through the switch. ARP is L3 CAM/ARP is L2


6

Please ping the DHCP machine before polling. After the ping, tables will be populated. If you can't ping the DHCP laptop, then you know why you can't see it in the ARP table.


6

This issue is a result of the engine-id changing. If you run into this syslog message, that is the exact definition of the problem. Nov 6 09:44:35 MHN00416AN01 snmpd[1260]: SNMPD_ENGINE_ID_CHANGED: Warning: Local engine ID has changed. Passwords for all the users under [edit snmp v3 usm local-engine] need to be reconfigured. Unfortunately, I have ...


6

Is this native to the 1900 series to only update the SNMP agent (forgive me if this is the wrong terminology) like it is doing at the moment. What you're seeing is expected behavior. IOS has cached IF-MIB statistics for on 10-second intervals (by default) for a while, for instance see this entry in the SNMP FAQ. That said, I have a few switches which ...


6

The ifCounterDiscontinuityTime is triggered when interfaces are dynamically removed from a device and then that same interface is dynamically re-added. I tested this using a loopback interface but I believe the behavior would be the same for modular interface whose existence would change based on whether or not the module was present. The steps to reproduce ...


6

SNMP counters will not be cleared while the device is up. The idea is that the software polling the counters will keep a tally of the current counter and simply looks at the delta since the last poll. See also this Cisco FAQ about SNMP counters, which says: Q. How do I poll queue limit drops on a router? A. With the use of SNMP, there is no way for the show ...


6

sysUpTime is a 32-bit counter and will roll over after 496 days. snmpEngineTime (.1.3.6.1.6.3.10.2.1.3) which returns the uptime in seconds and should not roll over for 135 years. snmpwalk -v2c -c xx 10.xx.xxx.xxx .1.3.6.1.6.3.10.2.1.3 SNMP-FRAMEWORK-MIB::snmpEngineTime.0 = INTEGER: 1701562 seconds snmpwalk -v2c -c xx 10.xx.xxx.xxx sysUpTime DISMAN-EVENT-...


6

Sadly the EX4200 (or any EX) is not able to do this. You would need a separate logical unit for the VLAN which has its own VLAN counters. This works for example on Junipers MX routers but not on EX. What you can do however is count the packets and bytes with a firewall filter. I have an working example here, for VLANS 14, 571, 572. You can of course use ...


6

As jonathanjo said in his answer and the comments afterwards, there are no special test traps for testing connectivity. Often, one of the RFC-defined traps (like linkup, linkdown or warmstart) is used. However, there is also MIB 1.3.6.1.4.1.8072.9999.9999, named netSnmpPlaypen. It was introduced by the net-SNMP project as a playground environment to ...


6

is it possible to add support for an OID that is not there by default? Unfortunately, adding support for these OIDs would require each of your vendors (Brocade and Dell) to implement them in their software images.


6

A layer-2 switch does not look at the layer-3 IP address on a packet to switch the layer-2 frames, and it only uses the MAC addresses on the frames for switching. The layer-3 interface on the switch is for switch management. It is like another host on the LAN, and it will not update its ARP table unless it communicates with a host at layer-3. Switches use a ...


5

You are polling a table with the known MAC addresses. It seems that your switch is connected to another one on port 24 so all MAC's that come from the other switch are seen on port 24. You can find a description of the SNMP MIB here : dot1dTpFdbStatus "Either the value '0', or the port number of the port on which a frame having a source address equal ...


5

We had the same issue and I found solution for it: It is called Expression MIB as per RFC 2982. You can do logical OR on this level by creating of new SNMP OID object which will be calculated at the same time as the SNMP Request comes to router/switch for this OID. Afterwards you can use this object to poll SNMP statistics of 2 or more ORed (via Expression ...


5

Your SNMP index may not match your port number. On some platforms, the indexes are not even persistent across reloads unless configured to be. I'd expect to find an interface speed of 2Gbps in your SNMPwalk for your 2-port LACP. You should scrutinize any ports showing a speed > 0 besides your physical ports 1-24 as possibly the LACP virtual interface. ...


5

The unit for ifSpeed is bits per second. This is in the description of the ifSpeed OID, down at the bottom of the link you supplied.


Only top voted, non community-wiki answers of a minimum length are eligible