• Arista 7280SE interoperability with Hitachi CB500 Blade Chassis

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There is a known issue when interconnecting the Arista 7280SE to the Hitachi CB500 blade chassis using the Hitachi 10G LAN PTM.  To work around this issue, Arista has implemented a CLI configuration option as of EOS-4.17.1F.  

In a nutshell, when connecting an Arista 7280SE to the Hitachi CB500 with copper twinax (10GBASE-CR), the link may not operate properly.  The symptoms of this behavior include the link status displaying either ‘not connect’ or ‘connect’ with no frames being received on the Arista 7280SE side of the connection.  FCS errors may or may not be incrementing on the Arista 7280SE interface counters.

The cause of this issue is an interaction between the Hitachi CB500 transmit signal, and the Arista 7280SE receiver.  The Hitachi CB500 disables its signal to the peer when the receive signal from that peer is lost.  Upon acquisition of the receive signal, the Hitachi CB500 transmits a marginal signal for an extended period of time.  During this time period, the Arista 7280SE will adapt to the signal before it is fully stabilized, resulting in a poor or unstable link condition.  This issue only occurs with copper twinax cables, and can thus be worked around by using optical media such as 10GBase-SR or 10GBase-SRL.

If copper twinax cables must be used, to solve the problem, Arista has implemented a configuration option to extend the time period during which the Arista 7280SE adjusts to the signal.  This is achieved via a new interface level command introduced in EOS-4.17.1F.  The command is configurable on a per interface basis, and can specify a delay of between 0 and 10000 ms.  When connecting to the Hitachi CB500 a value of 3500ms is recommended.  See below for an example usage of this command:

arista7280SE# configure

arista7280SE(config)# interface Ethernet1

arista7280SE(config-if-Et1)# hardware phy ?

  rx-signal      Receive signal

arista7280SE(config-if-Et1)# hardware phy rx-signal ?

  stabilization-delay     Stabilization delay

arista7280SE(config-if-Et1)# hardware phy rx-signal stabilization-delay 3500

arista7280SE(config-if-Et1)# show active | grep stabilization

   hardware phy rx-signal stabilization-delay 3500





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