Increase the Number of Nexus2000 Uplinks during operation

HUBERT RESCH · ‎12-07-2010

Hi there are two possibilities to connect FEX straightthrough to a Nexus5000.

1. with a normal 10GEC (max-links 1)

2. with hairpinning

So my question is for both scenarions: Is it possible to increase the number of uplinks during operation without interruption.

Unfortunately I am not able to test in advance.

I assume it schould be not be a problem if it configured via a channel, because just the number of channel-member changes.

Does anybody have any experience with this ?

ababakha · ‎12-07-2010

Hi Hubert,

Just to go over the two possibilities you mentioned. Basically you can have up to four max links meaning a group of host interface ports will be pinned to a certain uplink. Here is an example below:

switch# show interface ethernet 1/35 fex-intf
Fabric FEX
Interface Interfaces
---------------------------------------------------
Eth1/35 Eth100/1/12 Eth100/1/11 Eth100/1/10 Eth100/1/9
Eth100/1/8 Eth100/1/7 Eth100/1/6 Eth100/1/5
Eth100/1/4 Eth100/1/3 Eth100/1/2 Eth100/1/1

switch# show interface ethernet 1/33 fex-intf
Fabric FEX
Interface Interfaces
---------------------------------------------------
Eth1/33 Eth100/1/24 Eth100/1/23 Eth100/1/22 Eth100/1/21
Eth100/1/20 Eth100/1/19 Eth100/1/18 Eth100/1/17
Eth100/1/16 Eth100/1/15 Eth100/1/14 Eth100/1/13

switch# show interface ethernet 1/38 fex-intf
Fabric FEX
Interface Interfaces
---------------------------------------------------
Eth1/38 Eth100/1/36 Eth100/1/35 Eth100/1/34 Eth100/1/33
Eth100/1/32 Eth100/1/31 Eth100/1/30 Eth100/1/29
Eth100/1/28 Eth100/1/27 Eth100/1/26 Eth100/1/25

switch# show interface ethernet 1/40 fex-intf
Fabric FEX
Interface Interfaces
---------------------------------------------------
Eth1/40 Eth100/1/48 Eth100/1/47 Eth100/1/46 Eth100/1/45
Eth100/1/44 Eth100/1/43 Eth100/1/42 Eth100/1/41
Eth100/1/40 Eth100/1/39 Eth100/1/38 Eth100/1/37

The second option is that you can leave the max-links to 1 and have a port-channel fex link from the Nexus 5000 to the Nexus 2000. This is more a common network topology for fex redundancy.

Going back to your question, assumingly you're referring "channeling" to port-channel towards the fex i dont not see an issue as the max-links will be set to 1 and you're just binding an additional interface to the channel-group.

I hope this helps.

HUBERT RESCH · ‎12-07-2010

Hi,

and if we use hair-pinning and we increase max-links from 2 to 4 do you think we have to expect an interruption during doing this.

The Fexes in thze UCS-blade are connected via hairpinning to the 6100, changing the number of uplinks there end in short connectivity-loss to the fex.

Hubert

ababakha · ‎12-07-2010

I would expect brief interruption on your host interfaces would be repinning as per the above example. It is the same concept as the 6100 / fex pinning configuration.

HUBERT RESCH · ‎12-07-2010

Hi Andrew, how long is a brief interruption ? :-)

would you expect the the HIF are going down for a short time ?

Hubert

ababakha · ‎12-07-2010

I would expect the HIF to repin, the time it takes for the HIF to be active would be the same as when you changed the max-pinning on the 6100 . Just to give you an example, the moment you change the max-link number in N5k you get the following warning:

"Change in Max-links will cause traffic disruption"

HUBERT RESCH · ‎12-07-2010

Hi Andrew, thats a good tip:

..., the moment you change the max-link number in N5k you get the following warning:

"Change in Max-links will cause traffic disruption"

traffic-interruption is not so bad than interface-down would be, do you know if this happens.

Hubert

ababakha · ‎12-07-2010

I just tested this setup in the lab. Configuration steps below:

1. Configure "switchport mode fex" and "fex associate 100" on secondary interface.

2. No shut secondary interface.

3. Check to ensure secondary interface is up.

4. configure max pinning to 2. "(config-fex)# pinning max-links 2"

Results

======

1. if i run "show interface brief" straight after step for the fex ports will show as down status for approximately 2 seconds then come back up into forward status. See below:

Eth100/1/47 1 eth access down Link not connected 1000(D) --
Eth100/1/48 1 eth access down Link not connected 1000(D) -

Eth100/1/47 1 eth access up none 1000(D) --
Eth100/1/48 1 eth access up none 1000(D) -

Hope this helps you.

- Andrew