VSS Best practices

[marhifer2003]

Hi,

Cisco recommends not to use "mode on" on MECs. why?

Recommendations
* Always run L2 or L3 MEC.
* Do not use on and off options with PAgP or LACP or Trunk
protocol negotiation.
o PAgP — Run Desirable-Desirable with MEC links.
o LACP — Run Active-Active with MEC links.
o Trunk — Run Desirable-Desirable with MEC links.

Thanks in advance-

[krahmani323]

Hello Marhifer,

From the VSS Cisco validated design guide (CVD) regarding the MEC configuration mode

http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/VSS30dg/VSS-dg_ch2.html#wp1056543 (In Modes of PAgP Operation section).

Modes of PAgP Operation

Out of the three choices shown, the recommended mode for PAgP neighbors is desirable-desirable. This configuration option enables PAgP on both sides and forces the consistency check mentioned previously in this section. The desirable-desirable option is the best option for ensuring safe and reliable operation of MEC-connected devices.

LACP Mode of Operation

For the same reasons described in preceding PAgP description, table 2-5 shows only the best practice-based configuration options. Our of the three choices shown, the recommended mode for LACP neighbors is active-active

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On the other hand, the configuration of the Etherchannel mode for the VSL link must be set to on.

http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/VSS30dg/VSS-dg_ch2.html#wp1056015

Since VSL EtherChannel uses LMP per member link, the link-aggregation protocols, such as PAgP and LACP, are not required; each member link must be configured in unconditional EtherChannel mode using the channel-group group-number mode on command.

Hope that helps.

Thanks and regards

Karim

[marhifer2003]

Thank you krahmani323

Using "mode on" could cause any problem? we are experiencing some traffic losses intermitently.

Thanks in advance