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New Member

EvPC

Hi,

as per the new EvPC introduced with NX-OS 5.1(3)N1(1) described here (and announced somewhere in the forum by Lucien A.):

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/mkt_ops_guides/513_n1_1/n5k_enhanced_vpc.html

It seems, if I well understand, that a solution of this type is now supported:

GruppoIren.gif

But questions arises:

1 - what will be the preferred path for est-ovest flow, ie: from server A to server B? link B and then D? or A and then E?

2 - assuming that it will be link B and then link D what will happen to est-ovest flow in this scenario if links B goes down? The new flow will use A / C or A / E / D ?

Any suggestions will be appreciated :-)

Ciao e grazie!

Lucianno

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

EvPC

Hi Lucianno

Good thoughtful question. Channel hashing is a dynamic function and hence you cannot predict which parent Nexus 5k the FEX would send traffic to or which FEX fabric interface the Nexus 5k would pick.

However, the parent 5k will NOT send the traffic across peer-link(E in your topology) in your set up as long as the vPC to FEX stays up on both Nexus 5k switches.

Hope this helps.

Thanks

-Prashanth

3 REPLIES
Cisco Employee

EvPC

Hi Lucianno

Good thoughtful question. Channel hashing is a dynamic function and hence you cannot predict which parent Nexus 5k the FEX would send traffic to or which FEX fabric interface the Nexus 5k would pick.

However, the parent 5k will NOT send the traffic across peer-link(E in your topology) in your set up as long as the vPC to FEX stays up on both Nexus 5k switches.

Hope this helps.

Thanks

-Prashanth

New Member

EvPC

Ciao Prashanth,

now it's clear ... basically it's depending on how you set the balance algorithm and you can check this via "show" command (or "test" command, sorry but I don't remember well which one is for 6500 or for NX-OS ).

Thanks a lot!

Ciao Luciano

Cisco Employee

EvPC

Currently there is not a way to check on the FEX. But on the Nexus 5k, here is an example of me doing it in lab

N5K-B# show port-channel load-balance forwarding-path interface port-channel 996 vlan 620 src-ip 62.1.1.103 dst-ip 62.1.1.105 src-mac 0010.9462.0002 dst-mac 0010.9462.0006

Missing params will be substituted by 0's.

Load-balance Algorithm on switch: source-dest-ip

crc8_hash: 1    Outgoing port id: Ethernet2/16

Param(s) used to calculate load-balance:

        dst-ip:   62.1.1.105

        src-ip:   62.1.1.103

        dst-mac:  0010.9462.0006

        src-mac:  0010.9462.0002

N5K-B#

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