where do you recommend to situate IP addresses of iLo(remote consoles etc.) of the corporate servers? To create some internal LAN subnet behind NAT, or to choose IP addresses and protect them with ACLs ?
You should probably create an Out-Of-Band Management network. Best practices generally state to create a physically AND logically separate network for all management access like iLO, infrastructure monitoring, etc. Old 100Mbit switches will do just fine.
While it's tempting to have a completely separate network that unreachable to put your iLO(etc) on, I personally think that the benefits of having it accessible outweigh the security concerns.
I think the best practice would be to put it on a separate vlan and restrict access to that vlan. The key here is to not forget about remote access. You want to be able to get to your stuff at 3am.
The other thing here, if we're talking about iLO specifically, is monitoring. If you're using iLO, I'd highly recommend getting HP SIM. If it can talk to both the iLO and the box, it can get a ton of info and do things like file support calls with HP for you.
Hyppy mentions oob management, which makes complete sense for your networking equipment, but has much less benefit for the servers themselves (imho).