Ok, this sound might stupid - but is there any negative on just enabling jumbo frames in practice?

From what I understand:

• Any switch or ethernet adapter that sees a jumbo frame it can not handle will just drop it.
• TCP is not a problem as max frame size is negotiated in the setinuo phase.
• UCP is a theoretical problem as a server may just send a LARGE UDP packet that gets dropped on the way.

Practically though, as UDP is packet based, I do not really think any software WOULD send a UDP packet larger than 1500 bytes net without app level configuration changes - at least this is how I do my programming, as it is quite hard to get a decent MTU size for that without testing yourself, so you fall back in programming to max 1500 packets.

The network in question is a standard small business network - we upgraded now from a non managed 24 port switch to a 52 port switch with 4 10g ports (netgear - quite cheap) and will mov a file server to 10g for also ISCSI serving. All my equipment on the Ethernet level can handle minimum 9000 bytes and due to local firewalls I really want to get packets larger (less firewall processing), but the network is also NAT'ed to the internet. On top, different machines move around (download) large files (multi gigabyte area) quite often for processing.

The question is - can I expect problems when I just enable jumbo frames?

Again, this is not totally ignorance - I just don't see programs sending more than 1500 byte UDP packets (if that is a practical problem please tell me) and for TCP the MTU is negotiated anyway.

if there is a problem I can move to a dedicated VLAN, but this has it's own shares of problems as basically most workstations must then be on both VLAN's.