RG-S6120-20XS4VS2QXS VSU

Why did 2 RG-S6120-20XS4VS2QXS switches use 8 (4 each) 25g ports for VSU?

Support interface number	Interface attribute	Version condition	Maximum number of VSL links	Maximum number of VSU members	Other restrictions
1~6	Any 10 Gigabit optical port or more (Gigabit is not supported)	The VSU member devices must have the same software version	2	8	1. The same VSL link group supports mixed groups of 10 Gigabit ports, 25G ports, 40G ports and other interfaces with different rates. 2. In the same VSL link, the rate of the interfaces at both ends should be the same, and the speed should not be reduced (for example, the 25G port cannot be reduced to 10 Gigabit).

VSU general restrictions:
1, 40G one minute four port does not support VSL link.
2. Copper cable group VSU is prohibited for high-end subrack devices.
3, the VSL port does not support the rate of the port, only support the maximum rate of the port effective, such as 10 Gigabit port can only use 10 gigabit optical module networking, but can not use the gigabit optical module to self-adapt thousands of gigabit VSL link.
4. The rates of the interfaces at both ends of the VSL link must be consistent.