VSS Dual Active Detection methods

[rshum]

I'm reading the IOS 15.0 documentation for the VSS configuration. There are 2 ways to do the Dual Active Detection PAgP and Fast Hello. The documentation doesn't go into the pro's and con's of either one. Does anyone have experience with this and prefer one over the other? Can the PAgP be configured to go over the VSL ports?

Thanks

[jasonpresnell]

So it appears BFD has dropped off the list of dual-active detections for VSS at some code rev. I know for sure the SXI release it is still there. Not suprised as it was the slowest of the three and required yet another dedicated link. I have setups with both fast hello and ePagP going at the same time.

You should use both if your topology and port availability allow. You cannot use the VSL link for the dual-active detection, because the whole point of the detection is when the VSL links are no longer available.   IOS won't let you do this anyway. As for fast hello vslp, a dedicated ethernet link must be used. Up to 4 links can be used (obviously all dedicated and cannot be used for any other purpose). Not knowing which 15.0 you're going at, this documentation:

http://http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/15.0SY/configuration/guide/virtual_switching_systems.html#wp1063718

is good reference.

Both of these methods are pretty much even-steven in speed for detection. The detail is at this link:

http://www.cisco.com/en/US/products/ps9336/products_tech_note09186a0080a7c837.shtml#vsl_llr