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New Member

vlan-port instances?

Hi,

we found the following logging messages on a cat65k with sup720 from one of our customer:

"%PM-SP-4-LIMITS: The number of vlan-port instances on module 3 exceeded the recommended limit of 1800"

using the output interpreter we got this description:

"ERROR MESSAGE NOTIFICATIONS (if any)

%PM-4-LIMITS (x1): The number of vlan-port instances on [chars] exceeded the

recommended limit of [dec].

Explanation: This message means that the total number of individual VLAN ports,

counted over the module or switch, has exceeded the recommended limit. VLANs can

be counted more than once; if VLAN 1 is carried on ten interfaces, it will count

as ten VLAN ports. On some platforms bundling is also ignored for purposes of

this count; if eight interfaces on the same module are in one bundle, and the

port channel is carrying VLAN 1, it will count as eight VLAN ports. [chars] is

the module name (for example, switch or the module number), and [dec] is the recommended

limit.

Recommended Action: Reduce the number of trunks and VLANs configured in the module

or switch as recommended in [dec]. Enter the show interfaces trunk privileged

EXEC command to see the total number of trunks and VLANs."

I understand this description but has someone a background knowledge of "vlan-port instances" topic and can explain this

limitation on a more detailed level?

kind regards

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: vlan-port instances?

Hi,

Vlan-port instances refer to logical interfaces (trunks, etherchannels, physical ports, etc) on a given linecard. This is calculated as follows:

The sum of all logical interfaces (vlan-port) equals the number of trunks on the switch times the number of active VLANs on the trunks, plus the number of nontrunking interfaces on the switch.

This documented here, with the logical interface limits:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/ol_4164.htm#wp26366

HTH,

Bobby

*Please rate helpful posts

5 REPLIES
Cisco Employee

Re: vlan-port instances?

Hi,

Vlan-port instances refer to logical interfaces (trunks, etherchannels, physical ports, etc) on a given linecard. This is calculated as follows:

The sum of all logical interfaces (vlan-port) equals the number of trunks on the switch times the number of active VLANs on the trunks, plus the number of nontrunking interfaces on the switch.

This documented here, with the logical interface limits:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/ol_4164.htm#wp26366

HTH,

Bobby

*Please rate helpful posts

New Member

Re: vlan-port instances?

hi,

thanks for your immediate answer. using the information from the "show int trunk" output i've calculated that there are 2175 logical interfaces. referring to the release notes that's too much.

but additional question are left for me:

what happens to the switch resp. the spanning tree process, when exceeding this limit?

is there another solution than decreasing the number of active vlans an so the stp instances (they are useing rapid-pvst+) on the trunks?

kind regards,

Cisco Employee

Re: vlan-port instances?

Hi,

With 2175 logical interfaces, you are still exceeding the recommended maximum number of 1800 per module. How this will affect your switch is that the large number of logical interfaces will increase the convergence time of spanning tree.

Other than pruning unneeded vlans from trunks, you could migrate to MST, which has a per-module limit of 6000 logical interfaces per slot. However that would likely be much more painful than pruning your trunks.

HTH,

Bobby

New Member

vlan-port instances?

Hi Bobby,

Thanks for the answer. My question would be if pruning with VTP would reduce the number of port-vlan instances or must be done manually?

Thanks,

Csilla

New Member

Hi, I have the same issue on

Hi,

 

I have the same issue on module 9  but i don't know how to solve it and how can calculate the vlan on the trunk:

please check the attached file:

 

%PM-SPSTBY-4-LIMITS: The number of vlan-port instances on module 9 exceeded the recommended limit of 1800

 

 

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