Generic Systems vs. External Generic Systems
When to use a generic system and when to use an external generic system:
Generic System
- For attaching compute/storage
- Can only be connected to a single rack
- Appears in the topology as part of a rack
External Generic System
- For middleware devices, such as firewalls, load balancers, external routers and so on*
- Can be connected to multiple racks
- Appears in the topology outside of racks for easier identification
* In many cases, middleware boxes only connect to a single border leaf pair in a rack, but configuring it as an external generic system allows it to be visually separated outside of the rack. However, if there is a requirement such as connecting to an external router (MX) via BGP and you want to provide rack redundancy, then you would use an external generic system to allow this multi-rack connectivity.