MX960 SPC3 has 2 integrated sub-slots pic0 and pic1. Currently, pic0 is configured as mams interface, pic1 has no configuration.

Q1: If we also configure pic1 as mams interface, would it become active/backup, load-balance or what kind of redundancy could be achieved?

Q2: In the current configuration when mams is only using pic0, how the main board SPU is utilized, and how sub-slots (pics) SPU is utilized? is it used only of pic0 (128GB) and pic1 (128GB) is idle, or it is using 256GB from pic0 & pic1 together regardless of pic1 configurations?

Q3: By configuring pic1 also as mams interface, would we be able to reduce CPU load on pic0 and main control/switching units? Please advise, thanks. Prabin

MX960 chassis with one SPC3 card, which has 2 integrated sub-slots pic0 and pic1.

Three questions regarding the SPC3 card load-balance and redundancy issues, details explanation listed as below:

First, please treat PIC0 and PIC1 on the SPC3 card as separated/independent components, just like two separated physical interfaces.

Question 1~3 are similar questions regarding the SPC3 load-balance and N:1 redundancy issue, you can create the bundle of service interfaces (ams) for loading-balance and redundancy purpose. The concept is like ae bundle interfaces.

We have details in the document as below, the sample configuration also can be found in the left panel, SPU utilization will be dependent on the transient traffic and the services (NAT, firewall, IPsec etc) configured.

https://www.juniper.net/documentation/us/en/software/junos/interfaces-next-gen-services/topics/concept/usf-ams-understanding.html

In Junos OS, you can combine multiple services interfaces to create a bundle of services interfaces that can function as a single interface.

Traffic distribution over the member interfaces of an AMS interface can occur in either a round-robin fashion or hash-based. 

Because multiple service interfaces are configured as part of an AMS bundle, AMS configuration also provides for failover and high availability support. You can either configure one of the member interfaces as a backup interface that becomes active when any one of the other member interfaces goes down, or configure the AMS in such a way that when one of the member interfaces goes down, the traffic assigned to that interface is shared across the active interfaces.

Please read the article and the three related configuration documents.

NOTE – warm standby is a new feature.

In some scenarios, the customer would like to create multiple ams interfaces to process different class of traffic. In this case, warm standby is very useful. Let’s say you have two SPC3 card, each one has two PICs.

The customer can create 3 ams interfaces, and assign fpc0.pic0, fpc0.pic1, fpc1.pic0 into these three ams interfaces as primary member, and then assign fpc1.pic1 into these three ams interfaces as backup member, it is N:1 model.

Any of primary member failed, the service will fall back to the backup member. However, you need to fix the issue as soon as possible.

Starting in Junos OS Release 19.3R2, the N:1 warm standby option is supported on the MX-SPC3 if you are running Next Gen Services.