As I have passed the CCIE RS now you will see a bit more diversified post from me. I will
be blogging about topics mostly related to design and SP topics as that is what I am
most involved right now.

I did not have much experience with the Catalyst ME3400 so I want to do a post on the
basics about it.

The Catalyst ME3400 switch is a switch targeted at the service provider segment.
Although it is a Catalyst many things are different compared to the regular Catalyst

The ME3400 has three different port types:

UNI – User Network Interface. Port downstream (towards customer). Port can’t run STP,
CDP or Etherchannel protocols like PAgP and LACP.

ENI – Enhanced Network Interface. Also facing towards customer but this port can support
STP, CDP and Etherchannel protocols.

NNI – Network Node Interface. Sometimes also called network to network interface. This port
is facing upstream towards the core. This port has support for STP, CDP and Etherchannel

Lets take a look at the topology we are using which is the INE SPv3 topology. Here we are
focusing on 2 routers connected to a ME3400 switch.

By default the ME3400 behaves a bit different than other Catalysts. Let us take a look at
those defaults.

As you can see all the ports facing downstream are disabled by default. Not a big deal
but it’s a bit differen than what we are used to. The ports facing upstream(uplinks) are
enabled by default.

Now we take a look at the default port types.

All downstream ports are UNI by default and the uplinks are NNI by default. By default
the UNI ports can only communicate with NNI ports. This is very similar to how private
VLAN works very the isolated ports can only communicate through a promiscuous port.

The VLANs in the ME3400 are a bit different, they are called UNI-VLANs and by default
they work as isolated ports in private VLAN. That means that two UNI ports can’t
communicate directly even if in the same VLAN.

We will setup the ports towards the routers as access. On the ME3400
there are no dynamic modes so you need to set static or trunk or dot1q-tunnel
and also there is no support for ISL so there is no need to set the encapsulation.

We configure IP addesses on R1 and R2 and then we will try to ping between them.

And then the same on R2 with an IP of We check the status of the
switchport for R1.

It is set to access as expected and you can see that the port does not support
DTP. Now we try to ping between R1 and R2.

That was not successful. Do we see any MAC addresses?

Yes, that is not the issue. Are the ports forwarding in spanning tree?

No spanning tree? Remember, spanning tree does not run on UNI ports. The reason is
UNI ports can’t communicate with each other without going through a NNI port. So
how can we resolve so that R1 and R2 can ping each other? We can set one port to

Yes, that solved it. Now spanning tree is running on Fa0/1 because we changed
the port-type to NNI.

What if we can’t change the port-type? What else can we do? We can change the VLAN type.

So that works as well. By default UNI to UNI won’t communicate but we can change that
as you just saw. Note that spanning tree is not running now. This could potentially
lead to a loop.

To help protect against that we can change the ports to ENI and enable spanning tree
on them. We can also enable CDP so that the routers can see what they are connected to.

So by default this is how the traffic behaves on a Catalyst ME3400.

Now you know a bit more than before about the ME3400. It’s a nice switch and if you learn
the defaults you will figure it out pretty quickly.

A basic look at the Catalyst ME3400
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6 thoughts on “A basic look at the Catalyst ME3400

  • November 12, 2012 at 10:53 am

    Interesting post about Metro Ethernet and Cisco. In my company we use Alcatel-Lucent devices for metro ethernet network. If it’s possible please write more about SP world in Your posts! Cheers!

  • July 2, 2014 at 5:58 pm

    Could I use a ME3400 to build a CCNP Switch lab? Positioning this switch as a L3 switch?

    • July 7, 2014 at 8:41 am

      You could but it’s not an enterprise switch. So it’s quite different to say a 3560.

    • November 22, 2014 at 8:22 am

      Did you try the port-type command under the interface?

  • June 22, 2017 at 8:48 pm

    Thanks a lot for your post, great job !

    I have connected 2 laptops to uni interface and they are in vlan 2 set as uni-vlan community. Both laptops can reach each other. However when I configure int vlan 2 on ME3400, I can not ping int vlan 2 from laptops. Any idea ?


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