VSL link endpoints on totally different line cards

[Bojan Zivancevic]

Hi,

I would like to confirm that the following setup would work. Two chassis, two same supervisors (720-10G). One link in the VSL bundle is on the supervisors. OK so far.

There are also two line cards in these two chassis'. But one is, say, 6708-10GE and the other one is 6716-10GE. Can I use one port from 6708 and the other port from 6716 to form the second VSL link?

Based on what I have read on VSL forming, I did not see any complaints about the types of line card hardware. Seems the hardware check is being done on supervisors only.

Can somebody confirm this? Thanks.

[Reza Sharifi]

Hi,

Not sure if this is a typo or not but only Sup-VS-720 and Sup-2T support VSS. 

As for your other question, usually you only need 2 10Gig ports for VSL and best practice is to use one port from the sup and one port from a line card.  It could be either 6708 or 6716 (only non-oversubscribed ports) but since 6708 is 2 to 1 oversubscribe its a better choice.

see Q&A doc for more info:

http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-virtual-switching-system-1440/prod_qas0900aecd806ed74b.html

HTH

[jdesanti]

Hi Bojan,

Yes, you can use both linecards to form a VSL.

– WS-X6708-10G module: any 10 Gigabit Ethernet port

– WS-X6716-10G module: only non-oversubscribed ports can be used for VSL.

In other words, on 6708-10G you can use any port, but the 6716-10G will only support VSL in performance mode. The 6716-10G module consists of 4 port groups of 4 ports each:
• Port group 1: ports 1-4; port 1 is enabled in performance mode.
• Port group 2: ports 5-8; port 5 is enabled in performance mode.
• Port group 3: ports 9-12; port 9 is enabled in performance mode.
• Port group 4: ports 13-16; port 13 is enabled in performance mode.

Each port group can operate in either oversubscription mode or performance mode. In oversubscription mode, you can use up to 4 ports in the port group. In performance mode, only the first port of the port group is enabled, and that port comes with enhanced buffering and quality-of-service (QoS) functionality. The other 3 ports in the port group will be administratively shut down. The 6716-10G module works in oversubscription mode by default.

– WS-X6708-10G module: any 10 Gigabit Ethernet port

– WS-X6716-10G module: only non-oversubscribed ports can be used for VSL (supported with 12.2(33)SXI)

VSLs can carry regular data traffic in addition to the control plane communication between the two virtual switch members. The distance of VSL link is limited only by the chosen 10 Gigabit Ethernet optics. For example, with a X2-10GB-ER optic, VSL can span distance up to 40 km. (See Figure 3.)

Notice that the WS-X6716 can only use non-oversusbscribed ports but there is no similiar restriction for the 6708 module, although to be honest i am not sure why.

This is only for the VSL link though, not when you just use the module in a 6500 VSS pair.

The 16-port 10 Gigabit Ethernet module consists of 4 port groups of 4 ports each:
• Port group 1: ports 1-4; port 1 is enabled in performance mode.
• Port group 2: ports 5-8; port 5 is enabled in performance mode.
• Port group 3: ports 9-12; port 9 is enabled in performance mode.
• Port group 4: ports 13-16; port 13 is enabled in performance mode.

The command switch(config)#[no] hw-module slot x oversubscription port-group y
will put port group y (1, 2, 3, or 4) in performance mode and administratively disable the oversubscribed ports (ports 2-4 in port group 1, ports 6-8 in port group 2, ports 10-12 in port group 3, and ports 14-16 in port group 4) and put them in shutdown state. In this mode, you cannot do "no shut" on the disabled ports.

[Bojan Zivancevic]

Not sure you guys got me straight. Let me try to be more specific with a table drawing...

Chassis-1	VSL link	Chassis-2
SUP720-10G	<----------------->	SUP720-10G
6708-10GE	<----------------->	6716-10GE or even 6800 series...

So, these two 10GE cards should be in separate chassis'. From what I see it should work because the only line card constraint seems to be that it is capable of slapping a VSL header on the frame. This is why 6704 won't work for VSL links.

Would the switch complain about this kind of VSL link?

[jdesanti · Accepted solution]

The only limitation would be the different QoS architecture of the SUP and the modules, however the no mls qos channel-consistency command is automatically applied when you configure the VSL, so yes, your proposed set up will work.