Description

Attempting to convert a standalone SRX1500 configuration with two trunk ports to separate switches to a cluster configuration with redundant ethernet interfaces. Because the two interfaces are going to separate devices, the VLANs are defined on IRB logical interfaces.

When testing the configuration, the devices on one ethernet-switching reth interface are unable to communicate with devices on the other ethernet-switching reth interface, but are otherwise functioning expectedly when it comes to routing layer 3 traffic.

Symptoms

  • SRX cluster with reth interfaces set to ethernet switching and using IRB interfaces for routing is not forwarding the traffic between hosts due to IRB interfaces down

Solution

Check the following configuration parameters:

  • SRX is set to switching mode ("show ethernet-switching global-information" can be used)
  • IRB interfaces have a valid IP address
  • IRB interfaces are linked to the correct VLANs
  • Ethernet switching interfaces are up/up
  • VLANs exist on the device
  • There is a policy permitting the traffic
  • There are no filters blocking the traffic

 

If the configuration seems to be correct and still the IRB interfaces are up/down check the STP state of the IRB interfaces by executing "show ethernet-switching interface", if the STP state of the IRB interfaces is set to "Discarding" then this is probably the cause of the IRB interfaces being down. Note that the SRX may set these interfaces to this state if RSTP messages are being received on the physical interfaces and it is decided to block the IRB interfaces, monitor the traffic on the physical interfaces to confirm if RSTP traffic is being received (you can use "monitor traffic interface <physical-port> no-resolve").

 

If STP is not in use on the SRX then it may be necessary to stop sending RSTP messages on the SRX's neighbors towards the SRX's physical interfaces so that the IRB interfaces can come up and perform the proper routing.

 

To learn more about the STP states refer to: https://www.juniper.net/documentation/us/en/software/junos/stp-l2/topics/topic-map/spanning-tree-overview.html.

Modification History

2023-10-05 : Article Created
12/7/2023: Formatting corrections made.