Use of SNMP dynamic index, limitation?

[rimestad]

The manual explains how an ifDescr is mapped to a possible changing ifIndex. Then it warns, that each match will generate a snmp access, which may cause performance problems. I would like to do the mapping for approximately 200 Cisco devices with an average of 100 ifIndexes. How powerfull a hardware is needed for Zabbix to do that? Is there any other chic solution to my problem?

[rimestad]

Question withdrawn

Hi again,

Test with Zabbix shows severe performance problems using dynamic indexes. The system will indeed, as stated in the manual, cause heavy load on the router monitored. We measured 100% cpu load on a cisco 2610 series monitoring 100 interfaces for ifOperStatus up. For us this is a knock out creteria, so we withdraw our question.

Positive: We like the look and feel of Zabbix very much.

Chers Gunnar and Gert.

[Alexei]

Currently ZABBIX does not cache the index, thus it performs SNMP scan every time it uses the dynamic index. We are improving this in the next major release.

[rimestad]

When and how

Hi Alexei

We are improving this in the next major release.

When????

When we make 100 Dynamic index accesses a minute with the new caching release, will the SNMP gets then be reduced by a factor 100 relative to now? Will the caching time be adjustable?

Thanks for the answers.

Gert and Gunnar.

[Alexei]

When????

When we make 100 Dynamic index accesses a minute with the new caching release, will the SNMP gets then be reduced by a factor 100 relative to now? Will the caching time be adjustable?

The next major release is planned to be released in May.

It will be reduced by a factor of 2-1000 depending on number of SNMP gets required to find correct index.

I do not see what can be adjusted here.

[rimestad]

ifIndex to ifDescr may change anytime

I do not see what can be adjusted here.

Bigger devices like Cisco switches and routers may reorganize the interface table at any time. A common cause is a failing interface card forcing the device to unconfigure all lines on the card. This will reorganize the interface table. Replacing the card will cause a new reorganize. This is the default behaviour for Cisco IOS systems.

So any caching carry the risk of using obsolete indexing, causing reporting of wrong interfaces. A common fix is to read all needed information in bulk each time. Zabbix treats each item isolated and cannot know what to pick for other items. Any caching of ifIndex to ifDescr must timeout, so there is some optimum between "loading devices by picking to often" and "risk intermittend false observations due to caching".

That is why I ask

[mpotter-xiss]

Currently ZABBIX does not cache the index, thus it performs SNMP scan every time it uses the dynamic index. We are improving this in the next major release.

Is there any possibility of a patch for the 1.6 line to have caching for the dynamic indexing feature?

[szettervall]

Bigger devices like Cisco switches and routers may reorganize the interface table at any time. A common cause is a failing interface card forcing the device to unconfigure all lines on the card. This will reorganize the interface table. Replacing the card will cause a new reorganize. This is the default behaviour for Cisco IOS systems.

Use the following Cisco IOS command to keep your interface index persistnant between hardware/virtual interface changes.

snmp-server ifindex persist

[rimestad]

Known

Yes, this command is known. It is however quite an overhead to find the index numbers for 25.000 items and then feel sure not to use some wrong ones. We could write a program reading out the ifIndex to ifDescr, prepare a load file for Zabbix and load it this way, but then we feel like starting inventing the wheel a new.

Gert

[troffasky]

We could write a program reading out the ifIndex to ifDescr, prepare a load file for Zabbix

There's already a few programs that do this, but as you say the best solution would be for Zabbix to do it itself.

[Alexei]

Is there any possibility of a patch for the 1.6 line to have caching for the dynamic indexing feature?

It is unlikely. The functionality will require database changes which we cannot afford in a stable 1.6.x, unfortunately.

[vgray]

It is unlikely. The functionality will require database changes which we cannot afford in a stable 1.6.x, unfortunately.

we will wait this feature next major update

Thank you for zabbix.