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Cisco SCE 8000 10GBE Software Configuration Guide
OL-30621-02
Chapter 6 Global Configuration
Configuring Cisco Discovery Protocol
Cisco Discovery Protocol on the Cisco SCE 8000 Platform
Because the Cisco SCE 8000 platform functions differently from a router or a switch, there are several
unique features of CDP as supported on this device.
CDP Operational Modes on the Cisco SCE 8000
With a typical Cisco device, CDP is either enabled or disabled. When enabled, CDP packets are received
and transmitted. When disabled, CDP packets are discarded and no packets are transmitted.
The Cisco SCE 8000 is not a typical Cisco device. It is usually installed as a bump-in-the-wire device,
and transparently forwards packets from one interface to the corresponding interface. This behavior
conflicts with typical Cisco CDP packet processing; a typical Cisco device never forwards CDP packets
from one interface to another interface. To accommodate this behavior, the Cisco SCE 8000 extends the
enabled state with three different CDP modes:
•
Standard mode
: Standard CDP operation. CDP packets are received and processed, as well as
generated.
In this mode CDP functions as it does on a typical Cisco device. This mode should be used in most
cases, even though it is not the default mode.
•
Bypass mode
(default): CDP packets are received and transmitted unchanged. Received packets are
not processed. No packets are generated.
In this mode, “bump-in-the-wire” behavior is applied to CDP packets. This is the
backward-compatible mode, equivalent to not having CDP support.
•
Monitor mode
: CDP packets are received, processed, and transmitted unchanged. CDP packets are
analyzed and CDP neighbor information is available. No packets are generated.
In this mode “bump-in-the-wire" behavior is applied to CDP packets. This mode may be confusing
to operators and network management tools, because it is contrary to the concept of CDP as a
physical link protocol.
IP Network Prefix TLV
Contains a list of network prefixes to which the sending device
can forward IP packets. This information is in the form of the
interface protocol and port number, for example, Eth 1/0.
VTP Management Domain TLV
Advertises the system’s configured VTP management domain
name-string. Used by network operators to verify VTP domain
configuration in adjacent network nodes.
Native VLAN TLV
Indicates, per interface, the assumed VLAN for untagged packets
on the interface. CDP learns the native VLAN for an interface.
This feature is implemented only for interfaces that support the
IEEE 802.1Q protocol.
Full/Half Duplex TLV
Indicates status (duplex configuration) of CDP broadcast
interface. Used by network operators to diagnose connectivity
problems between adjacent network elements.
Table 6-1
Type-Length-Value Definitions for CDPv2 (continued)
TLV
Definition