Dell PowerConnect 6224 Release Note page 32

ICMP
Description
IPv4 Fragmentation support
ICMP Error message generation
ICMPv6 Packet Too Big
Multicast
Description
Multicast VLC streams are not
received on VLC client on complex
network topology.
30
User Impact
The switch is not fragmenting the datagram and forwards even when the
IP MTU of the forwarding Interface is set to a lower value (than the
datagram size).
This is a hardware limitation and is working as designed. The HW does
not allow the IP MTU to be configured per VLAN. We can configure the
maximum frame size in HW using the 'mtu' command in interface Ethernet
mode. However, if a packet exceeds the maximum frame size for a port, it
is discarded. If a packet happens to be sent to the software and it exceeds
the IP MTU, then the packet still will not be fragmented. An ICMP error
message is sent to the sender.
The ICMP Error Message generated by the switch has the fields (TTL)
unmodified instead of sending with a modified value resulted as a part of
forwarding process.
The system is not generating Packet Too Big message to the source when
it forwards the packet through an interface vlan with mtu smaller than the
packet being forwarded.
The PowerConnect 6200 Series switches do not have the capability to
enforce IP MTU on VLAN Routing interfaces..
User Impact
This is not a mainstream problem. DVMRP functionality works fine and
such issues are not seen in 2 or 3 router topologies. This issue is seen
only in complex topologies under high loads in the presence of other
multicast entries upon table full conditions.
System Firmware Version 3.2.0.6