Understanding Svi Autostate Exclude - Cisco Catalyst 4500 series Administration Manual

Chapter 34 Configuring Layer 3 Interfaces
Figure 34-2
Interface Ethernet

Understanding SVI Autostate Exclude

To be up/up, a router VLAN interface must fulfill the following general conditions:
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•
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Note The protocol line state for the VLAN interfaces comes up when the first switch port belonging to the
corresponding VLAN link comes up and is in spanning-tree forwarding state.
Ordinarily, when a VLAN interface has multiple ports in the VLAN, the SVI goes down when all the
ports in the VLAN go down. The SVI Autostate Exclude feature provides a knob to mark a port so that
it is not counted in the SVI up and down calculation and applies to all VLANs that are enabled on that
port.
A VLAN interface is brought up after the Layer 2 port has had time to converge (that is, transition from
listening-learning to forwarding). This prevents routing protocols and other features from using the
VLAN interface as if it were fully operational. It also prevents other problems from occurring, such as
routing black holes.
Understanding Layer 3 Interface Counters
Note Catalyst 4900M, Catalyst 4948E, Supervisor Engine 6-E, Supervisor Engine 6L-E, Supervisor Engine
7-E, Supervisor Engine 7L-E and Supervisor Engine 8-E , do not support Layer 2 interface counters.
However, they do support Layer 3 (SVI) interface counters.
When you run IPv4 and IPv6 on Catalyst 4900M, Catalyst 4948E, Supervisor Engine 6-E, Supervisor
Engine 6L-E, Supervisor Engine 7-E, Supervisor Engine 7L-E, and Supervisor Engine 8-E, packets are
routed in hardware by the forwarding engine. They support the following statistics for counting routed
packets with a maximum of 4092 interfaces:
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OL_28731-01
Physical Layer 3 Interfaces for the Catalyst 4500 Series Switch
Router
1.1.1.1
2/1
Host 1
Physical Inter-VLAN Routing on a Catalyst 4500 series switch
The VLAN exists and is active on the VLAN database of the switch.
The VLAN interface exists on the router and is not administratively down.
At least one Layer 2 (access port or trunk) port exists, has a link up on this VLAN, and is in
spanning-tree forwarding state on the VLAN.
Input unicast
Interface Ethernet
2.1.1.1
2/2
Host 2
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
About Layer 3 Interfaces
34-3