Cisco Catalyst 2960 Series, Руководство по настройке

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• It processes routing protocol messages and updates received from peer routers.
• It generates, maintains, and distributes the distributed Cisco Express Forwarding (dCEF) database to all
stack members. The routes are programmed on all switches in the stack bases on this database.
• The MAC address of the active switch is used as the router MAC address for the whole stack, and all
outside devices use this address to send IP packets to the stack.
• All IP packets that require software forwarding or processing go through the CPU of the active switch.
Stack members perform these functions:
• They act as routing standby switches, ready to take over in case they are elected as the new active switch
if the active switch fails.
• They program the routes into hardware.
If a active switch fails, the stack detects that the active switch is down and elects one of the stack members
to be the new active switch. During this period, except for a momentary interruption, the hardware continues
to forward packets with no active protocols.
However, even though the switch stack maintains the hardware identification after a failure, the routing
protocols on the router neighbors might flap during the brief interruption before the active switch restarts.
Routing protocols such as OSPF and EIGRP need to recognize neighbor transitions.
Upon election, the new active switch performs these functions:
• It starts generating, receiving, and processing routing updates.
• It builds routing tables, generates the CEF database, and distributes it to stack members.
• It uses its MAC address as the router MAC address. To notify its network peers of the new MAC address,
it periodically (every few seconds for 5 minutes) sends a gratuitous ARP reply with the new router MAC
address.
If you configure the persistent MAC address feature on the stack and the active switch
changes, the stack MAC address does not change for the configured time period. If the
previous active switch rejoins the stack as a member switch during that time period, the
stack MAC address remains the MAC address of the previous active switch. Note
• It attempts to determine the reachability of every proxy ARP entry by sending an ARP request to the
proxy ARP IP address and receiving an ARP reply. For each reachable proxy ARP IP address, it generates
a gratuitous ARP reply with the new router MAC address. This process is repeated for 5 minutes after
a new active switch election.
Partitioning of the switch stack into two or more stacks might lead to undesirable behavior
in the network.
Caution
If the switch is reloaded, then all the ports on that switch go down and there is a loss of traffic for the interfaces
involved in routing.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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Information About IP Routing