Cisco Discovery Protocol; Default Cdp Configuration - Cisco Nexus 3548 Configuration Manual
Nx-os interfaces release 9x
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Also See for Nexus 3548:
- Command reference manual (556 pages) ,
- Configuration manual (230 pages) ,
- Installation manual (112 pages)
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Cisco Discovery Protocol
Autostate behavior is the operational state of an interface that is governed by the state of the various ports in
its corresponding VLAN. An SVI interface on a VLAN comes up when there is at least one port in that vlan
that is in STP forwarding state. Similarly, this interface goes down when the last STP forwarding port goes
down or goes to another STP state.
By default, Autostate calculation is enabled. You can disable Autostate calculation for an SVI interface and
change the default value.
Note
Nexus 3000 Series switches do not support bridging between two VLANs when an SVI for one VLAN exists
on the same device as the bridging link. Traffic coming into the device and bound for the SVI is dropped as
a IPv4 discard. This is because the BIA MAC address is shared across VLANs/SVIs with no option to modify
the MAC of the SVI.
Cisco Discovery Protocol
The Cisco Discovery Protocol (CDP) is a device discovery protocol that runs over Layer 2 (the data link layer)
on all Cisco-manufactured devices (routers, bridges, access servers, and switches) and allows network
management applications to discover Cisco devices that are neighbors of already known devices. With CDP,
network management applications can learn the device type and the Simple Network Management Protocol
(SNMP) agent address of neighboring devices that are running lower-layer, transparent protocols. This feature
enables applications to send SNMP queries to neighboring devices.
CDP runs on all media that support Subnetwork Access Protocol (SNAP). Because CDP runs over the data-link
layer only, two systems that support different network-layer protocols can learn about each other.
Each CDP-configured device sends periodic messages to a multicast address, advertising at least one address
at which it can receive SNMP messages. The advertisements also contain time-to-live, or holdtime information,
which is the length of time a receiving device holds CDP information before discarding it. Each device also
listens to the messages sent by other devices to learn about neighboring devices.
The switch supports both CDP Version 1 and Version 2.
Default CDP Configuration
The following table shows the default CDP configuration.
Table 2: Default CDP Configuration
Feature
CDP interface state
CDP timer (packet update frequency)
CDP holdtime (before discarding)
CDP Version-2 advertisements
Cisco Nexus 3548 Switch NX-OS Interfaces Configuration Guide, Release 9x
6
Default
Setting
Enabled
60 seconds
180 seconds
Enabled
Configuring Layer 2 Interfaces
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