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New Member

Catalyst 5000, what is an LTL0 error ?


I've got a faulty Cat 5K supervisor 1 blade and was going to have a go at fixing it.

Does anyone know what "LTL0, LTL1, or LTL2 Error" during startup actually means ? All I can find is "LTLn Error is a local target logic error" but this doesn't help very much in narrowing down the fault !

Any help / ideas would be great,




Re: Catalyst 5000, what is an LTL0 error ?


This most likely indicates faulty HW (maybe memory on the module).

Check this link:

LTL Explanation:

Each line card has a local bus arbitrar, there is also a central arbitrar on the Supervisor module. Once the line card is granted access to the backplane (the switching bus), the packet is transmitted onto the switching bus where all cards in the system copy it. Line cards also tag the VLAN ID on the packet before sending it on the switching bus, so other components know which vlan did that packet come from.

The EARL (Encoded Address Recognition Logic), which resides on the supervisor card, inspects the destination address, source address and vlan id of the packet. The MAC address and vlan id are put through a HASH function, which results in a 15 bit address which gets inspected against the EARL tables.

As a result of a "hit" (if entry is found), information is sent via the result bus onto the LTL (local Target Logic) which selects which ports are to forward that packet. That information is then sent to the LTL of each line card in the system. Line cards that are supposed to forward that frame will send it out of the appropriate port. Other line cards will just drop that frame.

In case of a broadcast, or a "miss" in the EARL search, the MAC address along with the vlan id are sent on the result bus to flood on that vlan only. Special frame types like CDP and SPT are treated differently.

Hope this helps,


New Member

Re: Catalyst 5000, what is an LTL0 error ?

Thanks for the info.

A bit tricky to try and isolate the faulty component from this description. I think I need to fine someone who repairs these at a component level.



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