Nexus 7700 VPC Peer Link Recommendations

[B Y]

Let's say you were building 2 Nexus 7700 series with HSRP, VPC and fabricpath.  You need a 10g line card for connected firewalls and you use a 40g line card for downstream 5k's.  Port density does not dictate buying multiple of either line card so only 1 10g line card and 1 40g line card in each switch is required.

How would you run and configure your VPC peer links and peer keep alives?  I would suspect you have the following options:

1.  Use VPC object tracking.  Place peer links on 40g line card and KA on the 10g line card.  Track some downstream links to the 5k's along with the peer links in an attempt to pass the VPC primary role to the secondary switch in the event of 40g module failure.

2.  Buy another 40g line card even though it is not needed from a capacity standpoint. $$

3.  Attempt to use something like a QSFP-40G-SR4 optic in the 40g line cards operating as 4x10g.  Then bundle the 4x10g links with links from the 10g line card to provide redundancy across the modules.  Would I need to actually go QSFP-40G-SR4 to SFP-10G-SR or is it possible to break out to 4x10g but still utilize QSFP-40G-SR4 on both sides?

4.  Any other options I am not thinking about or something I have completely missed?

[Reza Sharifi]

For peer links you can have one 10Gig port from each line card and also use a 10Gig from one of the QSFP ports (40). This way you have 2 10Gig ports cumming from different line cards. For Keep-alive you can use the 1Gig out of band management port or 10Gig port, but 10Gig is way overkill.

HTH

[B Y]

Would I need to use QSFP-40G-SR4 broken out to 4x10g?  Then what would I use on the other side?  Can I use another QSFP-40G-SR4 broken out to 4x10g?  I assume I cannot use the 40g bidi in a 4x10g situation even if I have bidi on each side?

[Reza Sharifi]

Yes, the QSFP-40G-SR4 with a breakout cable on each device.How far apart are the switches?

I am not sure if you can use bidi but it is definitely more cost effective than QSFP-40G-SR4.

I use bidi to connect FEXs for 6ks. This is straight 40G.

HTH

[B Y]

Switches would just be 1 row apart and would be direct connected, no patch panel.  Could I use a standard MPO to MPO between the two without the fan/break out cable and still put it in 4x10g mode?  I would wind up with an MPO to MPO fiber between two QSFP-40G-SR4 and then one more regular SFP-10G-SR between 2 ports on the 10g line card all within a port channel.

[Reza Sharifi]

If the switches are less than 10 Meters apart you can use straight 40 with Twinax cable  That is what I use for peer-links (2 40s) but the switches are on top of one another.

HTH

[B Y]

I need to keep in 4x10G mode so I can channel them with links from the 10g module so I have module redundancy on the peer link. 

[Reza Sharifi]

Yes, sorry, I forgot that you only have 1 40 and 1 10gig module in each and not 2.

In that case. So, the solution with 1 10 from the 40 and one straight 10 to make a Portchannel should work

[B Y]

Not to beat it up but I am trying to figure out if I can take 4x10g from the single QSFP-40G-SR4 with an MPO to MPO to another QSFP-40G-SR4 making 4 individual 10 gig links.  Then just add 1 10 gig link from the 10 gig module.

[Reza Sharifi]

I have never try that before.  I have always used the breakout cable.

I am curious if that is actually possible.