At home I am using an ER poe 5 for about a year now to my satisfaction, I'm thinking of buying an ER 8/ER 8pro for use with my servers in the datacenter.
It would probably run with 2 ports in bonding for the public access and 2 ports in bonding for the private ports.
On the public ones it would run a BGP session to my provider which announces my IP block and some GRE tunnels and a few vlans.
At maximum it would be needed to being to use up to 1-2Gbit of throughput (no DHCP or pppoe) on both sides.
Can I use the ER 8 for this?