Switching ME Interface Characteristics

Introduction

The Catalyst ME 3400E has a number of differences than the Catalyst 3560. Port characteristics is the main difference especially when talking about port types such as UNI, NNI and ENI. All other ports are similar to regular switches such as:

  • Switch Ports
  • Port-Based VLANs
  • Access Ports
  • Trunk Ports
  • Tunnel Ports
  • Routed Ports
  • Ethernet Management Port
  • Switch Virtual Interfaces
  • EtherChannel Port Groups

UNI, NNI, and ENI Port Types

  • Ports types specific to Metro Ethernet switches are UNI, ENI and NNI.
  • UNI or ENI ports will only switch to NNI ports, to prevent customers being able to talk to each other.

UNI

  • Stands for User Network Interface.
  • Port that's designated to be downstream towards the customer. Usually it is connected to a host or an IP phone.
  • Changing port types does not shutdown the interfaces.
  • By default 10/100 ports are configures as UNI port type.
  • UNI ports, do not support running STP, CDP, LLDP, LACP and PAgP. ENIs support those.

NNI

  • Stands for Network Node Interface
  • Port that's designated to be upstream towards the service provider.
  • Typically a NNI port is configured to access other switches or routers (uplink to core).
  • Changing port types does not shutdown the interfaces.
  • By default SFP ports are configures as NNI port type.
  • By default, these ports are not shut down, unlike UNI.

ENI

  • Stands for Enhanced Network Interface
  • Port that's designated to be downstream towards the customer.
  • ENIs act just like the UNIs but with additional features that would have to be enabled manually, protocols like control protocols:
    • Cisco Discovery Protocol (CDP)
    • Spanning-Tree Protocol (STP)
    • Link Layer Discovery Protocol (LLDP)
    • EtherChannel Link Aggregation Control Protocol (LACP) or Port Aggregation Protocol (PAgP).
  • Changing port types does not shutdown the interfaces.
  • By default no ports are configures as ENI port type.

Dual-Purpose Ports

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SVI

  • VLAN interfaces can be configured on the ME switches. The only caveat in a specific scenario:
    • Host connected to a ME switch using an UNI or ENI port-type is not able to ping the local SVI, while traffic from NNI port-types can reach that SVI. The fix is to enable IP Routing on the switch.
    • The idea behind it might be that SVI's are used for MGR and only traffic from the network (NNI) should access it, while preventing customer access.

Relevant Commands

port-type (eni | nni | uni)

Specifies the port-type of a port, which defines port's functionality.

R1(config-if)#        port-type (eni | nni | uni)

Show port-type

Shows the ME port types.

show port-type

Additional Resources

Configuring Interface Characteristics - Cisco ME 3400E Ethernet Access Switch Software Configuration Guide, Rel. 12.2(55)SE

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