ExtremeXOS CDP Support

The ExtremeXOS-CDP implementation gathers information about network neighbors that support the Cisco Discovery protocol. This includes edge devices (VoIP phones) in the network-edge domain.

EXOS-CDP runs on top of the controlled port of an 802 MAC client. If port access is controlled by IEEE 802.1X, the port must be authorized before you enable CDP protocol receive functionality. CDP also runs over an aggregated MAC client, and the CDP protocol information must run over all the physical MAC clients of the aggregated ports. The spanning tree state of a port does not affect the transmission of CDP PDUs.

Each CDP message contains information identifying the source port as a connection endpoint identifier. It also contains at least one network address that can be used by an NMS to reach a management agent on the device (through the indicated source port). Each CDP message contains a time-to-live value, which tells the recipient when to discard each element of learned topology information.

By default EXOS-CDP feature is disabled.

Both CDP version 1 and version 2 are supported in EXOS-CDP implementation.

CDP Packet Format

The CDP control packets are encapsulated to the Sub-network Access Protocol (SNAP), and are sent as multicasts with Cisco -defined multicast MAC address 01:00:0C:CC:CC:CC.

The following table lists and describes the CDP packet fields.

Field Description
Version Version of the CDP being used values 0x1 or 0x02 (In our Implementation 0x01 will be used in this release)
Time-to-Live (TTL) TTL indicates the amount of time in seconds that a receiver should retain the information contained in this packet.
Check Sum Standard IP checksum
Type Indicates the type of the TLV
Length Indicates the total length of the Type,Length,Value fields
Value Indicates the value of the TLV

Different Types of TLVs

The following list identifies the different types of TLVs.

  • Device ID Information TLVs

    This TLV is used to identify Device name in form of Character string. In EXOS-CDP implementation it will be the configurable value. System Mac address will be the default Device Id.

  • Address Information TLVs

    This TLV contains a number that indicates how many addresses are contained in the packet, followed by one entry for each address being advertised. The addresses advertised are the ones assigned to the interface on which the CDP message is sent. A device can advertise all addresses for a given protocol suite and, optionally, can advertise one or more loopback IP addresses. If the device can be managed by SNMP, the first entry in the address type/length/value is an address at which the device receives SNMP messages. Maximum of 32 IP address are supported.

    The following table identifies and describes the various fields in the Address Information TLV.

    Field Description
    Protocol Type
    Protocol type It can be one of the following values
    1. NLPID
    2. 802.2 format
    Length Length of the protocol field.
    Protocol
    One of the following values:
    • 0x81—ISO CLNS (protocol type 3D 1)
    • 0xCC—IP (protocol type 3D 1)
    • 0xAAAA03 000000 0800—Pv6 (protocol type 3D 2)
    • 0xAAAA03 000000 6003—DECNET Phase IV (protocol type 3D 2)
    • 0xAAAA03 000000 809B—AppleTalk (protocol type 3D 2)
    • 0xAAAA03 000000 8137—Novell IPX (protocol type 3D 2)
    • 0xAAAA03 000000 80c4—Banyan VINES (protocol type 3D 2)
    • 0xAAAA03 000000 0600— XNS (protocol type 3D 2)
    • 0xAAAA03 000000 8019—Apollo Domain (protocol type 3D 2)
    Address Length Length of the address fields in bytes
    Address Address of the interface or the address of the system if addresses are not assigned to the interface.
  • Port ID TLVs

    The port ID type/length/value contains an ASCII character string that identifies the port on which the CDP message is sent. The type/length/value length determines the length of the string. In EXOS-CDP port description from the Pif structure is added in this TLV. If this Value is NULL then it will be the slot and port information.

  • Capabilities TLVs

    The capability TLV describes the device‘s functional capability. It can be set to one of the bits listed below.

    The following table identifies and describes the various bits in the Capabilities TLV.

    Bit Description Bit Description
    0x01 Performs level 3 routing for at least one network layer protocol.
    0x02 Performs level 2 transparent bridging.
    0x04 Performs level 2 source-route bridging. A source-route bridge would set both this bit and bit 0x02.
    0x08 Performs level 2 switching. The difference between this bit and bit 0x02 is that a switch does not run the STP.
    0x10

    Sends and receives packets for at least one network layer protocol. If the device is routing the protocol, this

    Bit should not be set.

    0x20 The bridge or switch does not forward IGMP Report packets on non-router ports.
    0x40 Provides level 1 functionality.
  • Version TLV

    The version TLV contains a character string that provides information about the software release version that the device is running. In EXOS-CDP version will be software version.

  • Platform TLV

    The platform TLV contains an ASCII character string that describes the hardware platform of the device. These platform TLV values are EXOS platform information that is the same seen when you issue the show switch command.

    Here are some of the possible string platform values

    • X440-24t-10G
    • X460-48t
    • BD-8810
  • Native VLAN TLV

    The native VLAN TLV indicates, per interface, the assumed VLAN for untagged packets on the interface. CDP learns the native VLAN for an interface. These Native VLAN values are taken from VLAN Manager APIs. In ExtremeXOS 21.1 both receive and transmit of this TLV is supported. This native VLAN will be granted the value of the VLAN statistically added value. This value will be retrieved from VIPF with Client usage as VLAN_CLIENT_STATIC.

  • Duplex TLV

    The duplex TLV indicates the duplex configuration of the interface. In ExtremeXOS 21.1 both receive and transmit of this TLV is supported.

  • Voice VLAN Query TLV

    The voice VLAN query TLV indicates what VLAN ID is to be used for voice. This TLV is mostly used in IP Phones to configure the voice VLAN. IP Phone will query the Neighbor switch/Router for voice VLAN. The Switch/Router will replay the VLAN ID value by transmitting in CDP PDU with type voice vlan reply TLV. In ExtremeXOS 21.1 only receive functionality is supported.

  • Voice VLAN Reply TLV

    The voice VLAN reply TLV indicates the voice VID for the VOIP VLAN Query. The switch/router will replay the VLAN ID value when it receives the voice vlan query TLV. In ExtremeXOS 21.1 only transmit functionality is supported. When the VOIP VLAN Query is received immediately a CDP PDU is sent with reply TLV filled.

  • Power TLV

    The power TLV indicates the amount of power consumed by remote devices. In ExtremeXOS 21.1 only receive functionality is supported.

  • Power Request TLV

    The power request TLV indicates the power requested by the IP phone . Only the receive functionality of this TLV is supported.

  • Power Available TLV

    The power available TLV indicates the power available in the powered source device. This information will be sent in the CDP PDU to the IP phone . Only the transmission of this TLV is supported.

  • MTU TLV

    The MTU TLV indicates the size of the largest datagram that can be sent/received by a remote device. In ExtremeXOS 21.1 only receive functionality is supported.

  • Trust Bit TLV

    The trust bit TLV offers the ability to specify whether the PC port of the phone is trusted. In ExtremeXOS 21.1 only transmit functionality is supported. This value is configured by CLI command to say whether the port is trusted/untrusted.

  • Untrust QOS TLV

    The untrust QOS TLV offers the ability to specify whether the PC port of the phone is untrusted then what to mark the L2 packet cos bit. In ExtremeXOS 21.1 only transmit functionality is supported. This value is configured by user through CLI command.

  • System Name TLV

    The system name TLV indicates the value of the remote device's sysName MIB object. In ExtremeXOS 21.1 both transmit and receive functionality is supported.

  • System Object ID TLV

    The system object ID TLV indicates the value of the remote device's sysObjectID MIB. In ExtremeXOS 21.1 only receive functionality is supported.

  • Management Address TLV

    The management address indicates the ipaddress for which the device accepts the SNMP messages. In EextremeXOS 21.1 both transmit and receive functionality is supported.

  • Location TLV

    The location TLV indicates the physical location, which says either the postal pin address. In ExtremeXOS 21.1 both transmit and receive functionality is supported. The location value will be configured by configure snmp syslocation sysLocation