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CDP & LLDP Questions

November 25th, 2019 Go to comments

Question 1

Explanation

Cisco Discovery Protocol (CDP) is a proprietary protocol designed by Cisco to help in finding information about neighboring devices. The default values are 60 seconds for advertisements. Each neighbor will keep the information contained in a packet for 180 seconds (holddown timer).

Question 2

Question 3

Explanation

CDP runs at Layer 2 so a router running CDP can see a Layer 2 switch that is directly connected to it, provided that the Layer 2 switch also runs CDP.

Question 4

Explanation

Unlike CDP, Link Layer Discovery Protocol (LLDP) is an open IEEE-standard (802.1AB) Layer 2 protocol used by network devices to share information about their identities and functionality with other network elements.

Question 5

Explanation

Cisco Discovery Protocol Version 2 provides more intelligent, device-tracking features than those available in Version 1. One of the features available is an enhanced reporting mechanism for more rapid error tracking, which helps to reduce network downtime. Errors reported include mismatched native VLAN IDs (IEEE 802.1Q) on connected ports and mismatched port-duplex states between connected devices. Messages about reported errors can be sent to the console or to a logging server.

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/xe-3s/asr903/cdp-xe-3s-asr903-book/nm-cdp-discover.html

Question 6

Explanation

Unlike CDP, Link Layer Discovery Protocol (LLDP) is an open IEEE-standard (802.1AB) Layer 2 protocol used by network devices to share information about their identities and functionality with other network elements.

Question 7

Explanation

Cisco devices send periodic CDP announcements to the multicast destination address 01-00-0c-cc-cc-cc out each connected network interface. These multicast packets may be received by Cisco devices. This multicast destination is also used in other Cisco protocols such as VTP.

Question 8

Explanation

The information contained in Cisco Discovery Protocol announcements depends on the device type and the version of the operating system running on it. The following are examples of the types of information that can be contained in Cisco Discovery Protocol announcements:
+ Cisco IOS XE version running on a Cisco device
+ Duplex setting
+ Hardware platform of the device
+ Hostname
+ IP addresses of the interfaces on devices
+ Interfaces active on a Cisco device, including encapsulation type
+ Locally connected devices advertising Cisco Discovery Protocol
+ Native VLAN
+ VTP domain

Cisco Discovery Protocol Version 2 provides more intelligent device tracking features than Version 1.

Question 9

Explanation

Media Endpoint Discovery is an enhancement of LLDP, known as LLDP-MED, that provides the following facilities:
+ Auto-discovery of LAN policies such as VLAN, Layer 2 Priority and Differentiated services (Diffserv) settings, enabling plug and play networking.
+ Device location discovery to allow creation of location databases and, in the case of Voice over Internet Protocol (VoIP), Enhanced 911 services.
+ Extended and automated power management of Power over Ethernet (PoE) end points.
+ Inventory management, allowing network administrators to track their network devices, and determine their characteristics (manufacturer, software and hardware versions, serial or asset number).

The LLDP-MED protocol extension was formally approved and published as the standard ANSI/TIA-1057 by the Telecommunications Industry Association (TIA) in April 2006.

Question 10

Explanation

LLDP supports a set of attributes that it uses to discover neighbor devices. These attributes contain type, length, and value descriptions and are referred to as TLVs. LLDP supported devices can use TLVs to receive and send information to their neighbors. This protocol can advertise details such as configuration information, device capabilities, and device identity.
The switch supports these basic management TLVs. These are mandatory LLDP TLVs.
+ Port description TLV
+ System name TLV
+ System description TLV
+ System capabilities TLV
+ Management address TLV
These organizationally specific LLDP TLVs are also advertised to support LLDP-MED.
+ Port VLAN ID TLV ((IEEE 802.1 organizationally specific TLVs)
+ MAC/PHY configuration/status TLV(IEEE 802.3 organizationally specific TLVs)

-> No VTP information is supported in LLDP.

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