Juniper SRX5800 Hardware Manual page 368

NOTE: To install additional SPCs in a services gateway that is part of a chassis cluster, it must
meet the following conditions.
Each services gateway must already have at least two SPCs installed in it.
To add first-generation SRX5K-SPC-2-10-40 SPCs, both of the services gateways in the cluster
must be running Junos OS Release 11.4R2S1, 12.1R2, or later.
To add second-generation SRX5K-SPC-4-15-320 SPCs, both of the services gateways in the
cluster must be running Junos OS Release 12.1X44-D10, or later.
To add next-generation SRX5K-SPC3 SPCs, both of the services gateways in the cluster must
be running Junos OS Release 18.2R1-S1, or later.
You must install SPCs of the same type and in the same slots in both of the services gateways
in the cluster. Both services gateways in the cluster must end up with the same physical
configuration of SPCs.
If you are only adding first-generation SRX5K-SPC-2-10-40 SPCs to the chassis, you must
install them so that the new SPCs are not the SPCs with the lowest-numbered slots in the
chassis. For example, if the chassis already has two SPCs with one SPC each in slots 2 and 3,
you cannot install additional SPCs in slots 0 or 1 using this procedure.
If you are adding second-generation SRX5K-SPC-4-15-320 SPCs to the chassis, you must
install the new SPCs so that a second-generation SRX5K-SPC-4-15-320 SPC is the SPC in the
original lowest-numbered slot. For example, if the chassis already has two first-generation
SPCs installed in slots 2 and 3, you must install SRX5K-SPC-4-15-320 SPCs in slots 0 or 1.
You will need to make sure that an SRX5K-SPC-4-15-320 SPC is installed in the slot providing
central point (CP) functionality so that the CP functionality is performed by an
SRX5K-SPC-4-15-320 SPC.
If you are adding next-generation SRX5K-SPC3 SPCs to the chassis, you must install the new
SPCs so that a next-generation SRX5K-SPC3 SPC is the SPC in the original lowest-numbered
slot. For example, if the chassis already has two second-generation SPCs installed in slots 2
and 3, you must install SRX5K-SPC3 SPCs in slots 0 or 1. You will need to make sure that an
SRX5K-SPC3 SPC is installed in the slot providing central point (CP) functionality so that the
CP functionality is performed by an SRX5K-SPC3 SPC.
NOTE: Your services gateway cannot have a mix of SRX5K-SPC-2-10-40 SPCs
and SRX5K-SPC3 SPCs, but starting with Junos OS release 18.2R2 and then
18.4R1 but not 18.3R1 you can have a mix of SRX5K-SPC-4-15-320 SPCs and
SRX5K-SPC3 SPCs.
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