This article outlines common checks and possible reasons for a redundant Ethernet (reth) interface not coming up on SRX devices.

After configuring a reth interface in an SRX chassis cluster, the interface remains down or does not transition to an active state.

When a reth interface does not come up, it is important to verify the configuration and status of the connected (adjacent) switch.

 

Ensure that the switch ports connected to the SRX nodes are configured as aggregated Ethernet (AE) interfaces and that LACP (Link Aggregation Control Protocol) is enabled, if LACP is being used on the SRX.

 

A mismatch in aggregation or LACP configuration between the SRX and the switch can prevent the reth interface from coming up.

 

Additionally, confirm that the deployment aligns with supported SRX chassis cluster design guidelines, especially when LACP is involved. Certain topologies and configurations have specific requirements, and deviations from supported designs may lead to interface issues.