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Polling 32-bit or 64-bit InOctets

Unanswered Question
Jun 2nd, 2009
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Hi all,

Can someone shed some light on when to poll 32-bit and when to poll 64-bit counters IfInOctet and IfHCInOctets ?

* Which counters are supported on which interfaces ?

I have seen routers which don't support the 64-bit counters (probably because it is not needed on a T1 interface for example). But i have also seen a 3750 switch which doesn't support it on a 1G interface (i assume this can be fixed with a firmware upgrade, no ?). However, are there any "rules" used by Cisco to determine when to support or implement the 64-bit counters ?

(i just converted all my graphs to 64-bit counters, now 20% of the graphs don't seem to support this counters. Before, i had 100% graphs, but any speed above 120 Mbit was inaccuratly graphed)



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Overall Rating: 4 (1 ratings)
David Stanford Tue, 06/02/2009 - 08:02
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According to RFC 2863, interfaces with an interface speed (ifSpeed) of 20M

bps and higher must instantiate the ifHC*Octets objects. The interfaces

without these objects are probably slower than that.

Actually, the RFC says that you only instatiate 32-bit counters for

interfaces with ifSpeed <= 20Mbs. You implement both for interfaces with

20 Mbs > ifSpeed < 650Mbs. After that, it's only 64-bit


It is a trade-off between the speed of the interface and the minimum time

to wrap. The 2863 guideline is provide 64-bit counters for interfaces

which might wrap in less than an hour.

That means that a 10/100Mbs

interface needs to provide 64-bit counters, but when the interface is

running at 10Mbs, it doesn't make any sense to disable the 64-bit

counters even though using the 32-bit counters is just fine. Even for

(fixed) higher-speed interfaces, if someone is willing to poll

them at the required rate, then it's fine to use them.

gnijs Tue, 06/02/2009 - 09:08
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Thanks you for your comments.

Can i conclude from your comments, that if the interface "might" wrap within an hour at maximum speed, Cisco will provide 64-bit counters, no matter what the actual speed is.

For example a 10/100/1000 interface might wrap easily within an hour at 1000 Mbps, but not at 10Mbps, so 64-bit counters are provided anyway, even when it run at 10 Mbit (speed 10) ??

(even though it is not strictly needed by the RFC at this speed ?)




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