Cisco Systems ME 3400 ACLs and Multicast Packets

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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 31 Configuring Network Security with ACLs
Using VLAN Maps with Router ACLs
Figure 31-7 Applying ACLs on Routed Packets
ACLs and Multicast Packets
Figure 31-8 shows how ACLs are applied on packets that are replicated for IP multicasting. A multicast
packet being routed has two different kinds of filters applied: one for destinations that are other ports in
the input VLAN and another for each of the destinations that are in other VLANs to which the packet
has been routed. The packet might be routed to more than one output VLAN, in which case a different
router output ACL and VLAN map would apply for each destination VLAN.
The final result is that the packet might be permitted in some of the output VLANs and not in others. A
copy of the packet is forwarded to those destinations where it is permitted. However, if the input VLAN
map (VLAN 10 map in Figure 31-8) drops the packet, no destination receives a copy of the packet.
Figure 31-8 Applying ACLs on Multicast Packets
Frame
Routing function
VLAN 10
Host A
(VLAN 10)
Packet
101359
VLAN 20
Host B
(VLAN 20)
VLAN 10
map
Input
router
ACL
Output
router
ACL VLAN 20
map
VLAN 10
map
Frame
Input
router
ACL
Output
router
ACL
Routing function
VLAN 10 VLAN 20
Host C
(VLAN 10)
Host A
(VLAN 10) Host B
(VLAN 20)
VLAN 20
map
Packet
101360