Forwarding Layer 3 Broadcast Packets - 3Com 5500-SI Configuration Manual

Forwarding Layer 3
Broadcast Packets
Table 258 Configuring the Filtering of Received Routes
Operation
Configure to filter the received
routing information distributed by
the specified address
Cancel the filtering of the received
routing information distributed by
the specified address
Configure to filter the received
global routing information
Cancel the filtering of the received
global routing information
By default, the filtering of received routes is not performed.
Configuring the Filtering of Distributed Routes
Define a policy concerning route distribution that filters the routing information that
does not satisfy the conditions, and distributes routes with the help of an ACL or
address ip-prefix.
Perform the following configuration in Routing Protocol View.
Table 259 Configuring to filter the distributed routes
Operation
Configure to filter the routes
distributed by the protocol
Cancel the filtering of the routes
distributed by the protocol
The route policy supports importing the routes discovered by the following protocols
into the routing table:
Direct—The hop (or host) to which the local interface is directly connected.
■
Static—Static Route Configuration
■
RIP—Route discovered by RIP
■
OSPF—Route discovered by OSPF
■
OSPF-ASE—External route discovered by OSPF
■
OSPF-NSSA—NSSA route discovered by OSPF
■
By default, the filtering of distributed routes is not performed.
Broadcast packets include full-net broadcast packets and directly connected broadcast
packets. The destination IP address of a full-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, for the switch also belongs to the
subnet. Since the VLAN of the switch isolates the broadcast domain, the switch will
Command
filter-policy gateway ip_prefix_name
import
undo filter-policy gateway ip_prefix_name
import
filter-policy { acl_number | ip-prefix
ip_prefix_name } [ gateway ] import
undo filter-policy { acl_number | ip-prefix
ip_prefix_name } [ gateway ] import
Command
filter-policy { acl_number | ip-prefix
ip_prefix_name } export [ routing_process
undo filter-policy { acl_number | ip-prefix
ip_prefix_name } export [ routing_process ]
IP Routing Policy 263