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A policy matches nodes in priority order against packets. If a packet matches the criteria on a node,
it is processed by the action on the node. If the packet does not match the criteria on the node, it
goes to the next node for a match. If the packet does not match the criteria on any node, it is
forwarded according to the routing table.
PBR and Track
PBR can work with the Track feature to dynamically adapt the status of an action to the availability
status of a tracked next hop.
•
When the track entry changes to
Negative
, the action is invalid.
•
When the track entry changes to
Positive
or
NotReady
, the action is valid.
IGMP snooping
IGMP snooping runs on a Layer 2 device as a multicast constraining mechanism. It creates Layer 2
multicast forwarding entries from IGMP packets that are exchanged between the hosts and the
Layer 3 device.
The Layer 2 device forwards multicast data based on Layer 2 multicast forwarding entries. A Layer 2
multicast forwarding entry contains the VLAN, multicast group address, multicast source address,
and host ports. A host port is a multicast receiver-side port on the Layer 2 multicast device.
MLD snooping
MLD snooping runs on a Layer 2 device as an IPv6 multicast constraining mechanism. It creates
Layer 2 IPv6 multicast forwarding entries from MLD packets that are exchanged between the hosts
and the Layer 3 device.
The Layer 2 device forwards multicast data based on Layer 2 IPv6 multicast forwarding entries. A
Layer 2 IPv6 multicast forwarding entry contains the VLAN, IPv6 multicast group address, IPv6
multicast source address, and host ports. A host port is a multicast receiver-side port on the Layer 2
multicast device.
DHCP
The Dynamic Host Configuration Protocol (DHCP) provides a framework to assign configuration
information to network devices.
A typical DHCP application scenario has a DHCP server and multiple DHCP clients deployed on the
same subnet. DHCP clients can also obtain configuration parameters from a DHCP server on
another subnet through a DHCP relay agent.
DHCP server
The DHCP server is well suited to networks where the following conditions exist:
•
Manual configuration and centralized management are difficult to implement.
•
IP addresses are limited. For example, an ISP limits the number of concurrent online users, and
users must acquire IP addresses dynamically.
•
Most hosts do not need fixed IP addresses.
The DHCP server selects IP addresses and other parameters from an address pool and assigns
them to DHCP clients. A DHCP address pool contains the following items:
•
Assignable IP addresses.
