VSS Layer 3 Etherchannel Problem

Unanswered Question
Dec 19th, 2009

Hi Guys,

I am having an issue connecting two pairs of VSS switches.

I have set up a port channel as follows on Switches 1 and 2

int port-channel 200

ip address 10.x.x.1 255.255.255.252

Int Ten 1/1/1

channel-group 200 mode desirable

Channel-protocol pagp

Int Ten 2/1/1

channel-group 200 mode desirable

Channel-protocol pagp

I have set up a port channel as follows on Switches 3and 4

int port-channel 200

ip address 10.x.x.2 255.255.255.252

Int Ten 1/1/1

channel-group 200 mode desirable

Channel-protocol pagp

Int Ten 2/1/1

channel-group 200 mode desirable

Channel-protocol pagp

They are connected via LR x2's, However I was getting constant errdisable due to UDLD, I tried new ports, new x2's and fibres but still the same...

Hence I turned udld guard off and I now get "PAGP not supported by remote port"

Any ideas??

Thanks

Scott

I have this problem too.
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Reza Sharifi Sat, 12/19/2009 - 11:45

Hi Scott,

Couple of questions:

Are the two VSS pairs fully meshed?

from switch 1 in pair 1 ports 1/1/1/ and 2/1/1 also 1/1/2 and 2/1/2

Are you using a different domain IDs for each VSS pair?

Reza

scott-goodwin Sat, 12/19/2009 - 12:43

Hi,

They all do have the same domain id.

The two Test VSS are simply connected together via one ten gig interface, the live core that i am trying to connect too has 2 VSS links 1 on the TenGig line card and one on the sup, it is also running Fast-Dual Active Detection on the Sup - Sup Copper Gig port.

As for the two uplinks I am just going switch 1 to switch 1 and switch 2 to switch 2 so no not fully meshed.

Cheers

Scott

Reza Sharifi Sat, 12/19/2009 - 15:45

Hi,

It is recommended and best practice to always duel home the VSS bundle together

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

Also, the domain ids should be different for each VSS set.

Multiple deployments of Cisco Virtual Switching System can exist in a given network design, adding to the availability and scalability of the network. As a result, Cisco requires you use unique virtual switch domain identifiers for each pair of VSS switches

http://www.ciscosystems.lt/en/US/prod/collateral/switches/ps5718/ps9336/white_paper_c11_429338.pdf

HTH

Reza

scott-goodwin Sun, 12/20/2009 - 02:18

Hi Reza,

I will change the Domain ID and also bring up the second link. Do you think this will stop the issue with interconnects?

Thanks

Scott

Reza Sharifi Sun, 12/20/2009 - 07:29

Scott,

With my experience and testing, I have found out that VSS works really good if it is configured correctly with the right software and hardware, if not it can cause major outage and troubleshooting can get very confusing.

I would defiantly make these changes and test again.

Are these switches far form each other?

It that why you are using LR modules versus SR?

Thanks,

Reza

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