Configuring To Forward Layer 3 Broadcast Packets - H3C S7500 Series Operation Manual

Operation Manual – IP Address-IP Performance-IPX
H3C S7500 Series Ethernet Switches
Configure to send TTL
timeout packets and
unreachable packets
to CPU

2.5 Configuring to Forward Layer 3 Broadcast Packets

Broadcast packets include total-net broadcast packets and directly-connected
broadcast packets. The destination IP address of a total-net broadcast packet is all 1s
(255.255.255.255) or all 0s. A directly-connected broadcast packet is a packet whose
destination IP address is the network broadcast address of a subnet, but the source IP
address is not in the subnet segment. When a switch forwards this kind of packet, the
switch cannot tell whether the packet is a broadcast packet if the switch is not
connected with the subnet.
If a broadcast packet reaches the destination network after being forwarded by the
switch, the switch will receive the broadcast packet, because the switch also belongs to
the subnet. Because the VLAN of the switch isolates the broadcast domain, the switch
will stop forwarding the packet to the network. Using the following configuration tasks,
you can choose to forward the broadcast packet to the network for broadcast.
Follow these steps to configure to forward layer 3 broadcast packets in system view:
Enter system view
Configure to forward
Layer 3 broadcast
packets
To do...
command...
ip { ttl-expires |
unreachables }
To do...
system-view
ip forward-broadcast
Chapter 2 IP Performance Configuration
Use the
Required
By default, Unreachable packets are
not sent to the CPU, while TTL
timeout packets are sent to the CPU
Use the command...
2-3
Remarks
Remarks
—
Required
By default, the switch
does not forward Layer 3
broadcast packets.