H3C Technologies H3C S10500 Series Switches - Manual (Page 101)

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NOTE:
•
If an ACL is referenced in the ip forward-broadcast command, only packets permitted by the ACL can
be forwarded.
• If you repeatedly execute the ip forward-broadcast command on an interface, only the last executed
command takes effect. If the command executed last does not include acl
acl-number, the ACL
configured previously is removed.
Configuration example
Network requirements
As shown in Figure 42 , the host’s interface and VLAN-interface 3 of the switch are on the same network
segment (1.1.1.0/24). VLAN-interface 2 of Switch and the server are on another network segment
(2.2.2.0/24). The default gateway of the host is VLAN-interface 3 (IP address 1.1.1.2/24) of Switch.
Configure the switch so that the server can receive directed broadcasts from the host to IP address
2.2.2.255.
Figure 42 Network diagram for receiving and forwarding directed broadcasts
Configuration procedure
# Enable the switch to receive directed broadcasts.
system-view
[Switch] ip forward-broadcast
# Configure IP addresses for VLAN-interface 3 and VLAN-interface 2.
[Switch] interface vlan-interface 3
[Switch-Vlan-interface3] ip address 1.1.1.2 24
[Switch-Vlan-interface3] quit
[Switch] interface vlan-interface 2
[Switch-Vlan-interface2] ip address 2.2.2.2 24
# Enable VLAN-interface 2 to forward directed broadcasts.
[Switch-Vlan-interface2] ip forward-broadcast
Configuring TCP attributes
Configuring TCP path MTU discovery
TCP path MTU discovery (in RFC 1191) discovers the path MTU between the source and destination ends
of a TCP connection. It works as follows:
1. A TCP source device sends a packet with the Don’t Fragment (DF) bit set.
2. A router that fails to forward the packet because it exceeds the MTU on the outgoing interface
discards the packet and returns an ICMP error message, which contains the MTU of the outgoing
interface.