NetScaler VPX in SDX drops traffic when LACP link is restored
Article ID: CTX232956
Updated On:
Description
NetScaler VPX in SDX drops traffic for around 30 seconds, when one shutdown link within a two link LACP channel is restored.
Resolution
Best current option is to enable Fast LACP. An enhancement request was filled: RFE ID-004794.
"The traffic drop for about 30s is due to the fact that interface at the VPX takes around 30s extra than Dom0 to come to DISTRIBUTING state.
Here is the explanation for this behavior.
In SDX, the main LACP protocol runs between Dom0 and the partner switch. The VPXs level LACP is only in listen mode, that means it only receives LACPDUs from switch and Dom0.
When link shut/no-shut is down, the link at Dom0 comes UP first and the link at the VPX takes few extra seconds to come UP. As soon as the link at Dom0 comes UP it will start exchanging LACPDUs with the switch and comes to DISTRIBUTING state. When this initial exchange of LACPDUs is happening, the VPX level link is not yet UP, so it doesn't get any of the LACPDUs. By the time link comes UP in VPX, the LACPDU exchange rate is set to 30s due to long timeout. So when the next LACPDU is received after 30s, the link at VPX also goes to DISTRIBUTING state and starts processing other traffic.
Problem Cause
RFE ID-004794 SDX 14k dropping traffic after restoring one LACP link."The traffic drop for about 30s is due to the fact that interface at the VPX takes around 30s extra than Dom0 to come to DISTRIBUTING state.
Here is the explanation for this behavior.
In SDX, the main LACP protocol runs between Dom0 and the partner switch. The VPXs level LACP is only in listen mode, that means it only receives LACPDUs from switch and Dom0.
When link shut/no-shut is down, the link at Dom0 comes UP first and the link at the VPX takes few extra seconds to come UP. As soon as the link at Dom0 comes UP it will start exchanging LACPDUs with the switch and comes to DISTRIBUTING state. When this initial exchange of LACPDUs is happening, the VPX level link is not yet UP, so it doesn't get any of the LACPDUs. By the time link comes UP in VPX, the LACPDU exchange rate is set to 30s due to long timeout. So when the next LACPDU is received after 30s, the link at VPX also goes to DISTRIBUTING state and starts processing other traffic.
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