Port and Interface Frequently Asked Questions

For frequently asked questions about all services and support, see the PacketFabric FAQ.

Cross Connects and LOAs

What is an LOA?

LOA stands for Letter of Authorization or Letter of Authority. They are also sometimes called LOA-CFAs (Connecting Facility Assignment).

The LOA is required to install a cross connect between your equipment and ours.

The LOA tells the data center three things:

1.) You have permission to connect your equipment with ours.

2.) The exact location of the port at which they should install the physical cross connect.

3.) The media they should use for the connection.

Click here to download a template.

For more information, see Cross Connects.

The data center cannot install my cross connect because the port is occupied. What does this mean?

We pre-cable the rear side of all our panels. Sometimes data center technicians will mistake this to mean that the port is already occupied. However, the front side of the panel should be open for new cross connects.

If they are still reporting that the port is occupied after checking the front panel, it is possible that the previous cross connect was never removed. To have us verify this for you, open a ticket by emailing support@packetfabric.com.

Why do some of my ports allow me to order a cross connect while others don’t?

The ability to order a cross connect through the PacketFabric portal depends on the data center. If you do not see the Cross Connect action in the port’s overflow menu, you will need to generate an LOA and contact the data center directly with your request.

For more information, see Cross Connects.


Do you support jumbo frames? What MTU do you support?

Yes, we support jumbo frames.

All our interfaces support an MTU of 9096 at layer 2. However, there might be additional overhead for VLAN tagging used on EVPL circuits.

Why is the interface MTU fixed at 9096 bytes?

An MTU of 9096 bytes is the largest Layer 2 frame that PacketFabric will ever send to or receive from your interface.

This value is derived from: 9192 (minimum internal MTU) - 96 (PacketFabric overhead) = 9096

How many bytes should I set for my MTU?

Your MTU should be 9000 or 8192 bytes for optimal performance.

PacketFabric automatically configures your interfaces at a Layer 2 MTU of 9096 bytes. The suggested size of 9000 bytes covers most variances in multiple platforms and vendor inconsistencies in regards to the system and port level MTUs on devices.

Depending on the release date and the platform, a system MTU of 1500 actually translates to a Layer 2 MTU of 1514 or 1522 (depending on feature set). Some platforms only configure the Layer 2 MTU. The operator needs to be aware of ethernet and additional feature overhead when changing the MTU.