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Layer two (layer 2) protocol packets does not pass though the VMAN tunnel after upgrade of EXOS

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TitleLayer two (layer 2) protocol packets does not pass though the VMAN tunnel after upgrade of EXOS
Symptoms
Following layer two (layer 2) protocol packets stopped passing through VLAN / VMAN  VPLS / VPWS after upgrade to 15.4 or higher. 

• Cisco Discovery Protocol (CDP)
• Unidirectional Link Detection (UDLD)
• VLAN Trunking Protocol (VTP)
• Port Aggregation Protocol (PAgP)
• Dynamic Trunking Protocol (DTP)
• Link Aggregation Control Protocol (LACP)
• Link Layer Discovery Protocol (LLDP)
• Spanning Tree Protocol (STP)
• Extreme Discovery Protocol (EDP)


This article focuses on the resolution to allow CDP packets across the VMAN/VLAN. 
Environment
  • EXOS 15.4 or higher
  • Summit and BlackDiamond series
Cause
Prior to 15.4 EXOS version CDP support is not available, since the feature to support CDP is introduced from 15.4 the switches by default would start processing the CDP packets hence not letting them to pass through the tunnnel
Resolution
Layer 2 Protocol Tunneling

Layer 2 protocol tunneling (L2PT) is achieved by encapsulating the PDUs at the ingress PE device
before transmitting them over the service provider network. The encapsulation prevents the PDUs from
being processed by the switches in the SP network. At the egress PE device, the encapsulated packets
are de-encapsulated, and transmitted to the CE device.

Sample configuration commands to allow CDP packets
1. Create a L2PT profile
          "create l2pt profile Allow-cdp"
2. The Protocol filter for CDP is created by default and hence there is no need to create a separate filter and define ether type or destination-address. 
3. Map the protocol filter to the L2PT profile
       "configure l2pt profile "Allow-cdp" add protocol filter "cdp" action tunnel"
4. Associate the L2PT profile which is newly created to the customer edge or ingress port of the VMAN where you want to tunnel the CDP packets.
    "configure vman <VMAN NAME> ports 1 l2pt profile "Allow-cdp""
5. Verify the L2PT is applied to the VMAN 
      " show vman <VMAN NAME> l2pt detail"



 
Additional notes
 Sample configuration for the topology below:

User-added image

VMAN SW1 and SW2 configuration:
 
create vman test tag 100
configure vman test add port 3 tagged
configure vman test add port 1 untagged
create l2pt profile allowcdp
configure l2pt profile allowcdp add protocol filter cdp
configure vman test port 1 l2pt profile allowcdp

To verify if l2pt profile is working, execute the command "show vman <vman name> l2pt detail" 
 
show vman test l2pt detail
Port 1
    L2PT Profile Name      : allowcdp

    Protocol Filter Name   : cdp
        Destination Address: 01:00:0c:cc:cc:cc
        Protocol Id Type   : snap
        Protocol Id Value  : 0x2000
        Field Offset       :
        Field Value        :
        Field Mask         :
        Action             : Tunnel
        CoS                :
        Packets Transmitted: 95
        Packets Received   : 87

Port 3
    L2PT Profile Name      : (none)

    Protocol Filter Name   : (Implicit configuration)
        Destination Address: 01:00:0c:cc:cc:cc
        Protocol Id Type   : snap
        Protocol Id Value  : 0x2000
        Field Offset       :
        Field Value        :
        Field Mask         :
        Action             : Encap
        CoS                :
        Packets Transmitted: 87
        Packets Received   : 91



For more information on the L2PT  please refer to the section Layer 2 Tunneling and Filtering in the user guide (  Where can I find documentation for Extreme products? )

Related Articles:
How to configure l2pt profile in Extreme Switches

 

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