MCR Advanced VLAN and Routing Features

The Megaport Cloud Router (MCR) is easy to configure for IP routing without needing to understand complex network protocols. This topic describes the MCR advanced VLAN and routing features that extend an MCR’s capabilities beyond the default settings.

MCR Looking Glass

The MCR Looking Glass provides single-screen visibility into traffic routing. This visibility helps you troubleshoot connections by showing the status of protocols and routing tables in the MCR.

For more information, see Viewing Traffic Routing through the MCR Looking Glass.


The Q-in-Q Connection option allows either a single VLAN (non Q-in-Q, also known as 802.1Q) or stacked VLANs (Q-in-Q, also known as 802.1ad) to be carried over a VXC. In most cases, you’ll use a single VLAN that is exposed on the destination physical port as a trunked port instance, allowing the port to contain multiple VXCs to destinations other than the MCR being configured.

For certain use cases, you might need multiple inner VLANs exposed to a Port using Q-in-Q.

For more information on Q-in-Q, see Configuring Q-in-Q.


MCR supports the standard Ethernet MTU of 1500 bytes.

Public IP address allocation

When ordering the MCR, public IP addresses are provided as needed, based on specific CSP requirements. Megaport will allocate up to a /29 free of charge from the Megaport address space for this connectivity. You can also use your own public IP addresses.

For an Azure ExpressRoute primary and secondary IP address, Megaport provides a /30 or 4 addresses for each.


You can enable Message Digest 5 (MD5) authentication between two eBGP neighbors to have MCR verify each segment sent on the connection between the neighbors.

Routing features

MCR manages both static and dynamic routes, up to 10,000 routes. These routing options are available for individual configuration of each sub-VLAN (C-Tag) on Q-in-Q capable connections.

Dynamic routing

Dynamic routing propagates route table updates from the MCR across the VXC to the destination Port. MCR leverages the Border Gateway Protocol (BGP) to provide flexible routing by exchanging routing information between peers.

MCR supports these BGP routing features:

Bidirectional Forwarding Detection (BFD)

The BFD protocol detects path failure between directly connected BGP peers, allowing for a faster BGP routing re-convergence time. Enabling BFD on a VXC connection provides fast link failure detection and failover when connecting to services that support BFD on the remote peer. After BFD is enabled, a BGP peer relationship can be torn down quickly after notifications from BFD, failing over to another BGP peer. BFD is enabled on a VXC connection.

For information on the BGP BFD setting, see Configuring the BFD protocol.

Multiple Exit Discriminator (MED)

A Multiple Exit Discriminator (MED) is a BGP path attribute that can influence a BGP peer to take a preferred route when the advertising AS is the same for candidate routes and there are multiple entry points for that AS. A lower MED metric is preferred over a higher metric. MED is enabled on a VXC connection.

For information on the MED setting, see Configuring a preferred route.

BGP on/off toggle

BGP shutdown provides an easy way to administratively shut down a BGP connection without removing it. This feature can be useful while setting up a new route, performing maintenance, and so on.

For information on the BGP shutdown setting, see Shutting down a BGP connection.

Static routing

Without BGP, MCRs use static routing to directly connect manually configured routes that access a single route. Static routing is generally used in place of BGP when a customer device does not support BGP or the target device requires manually configured IP addressing and routes.

For information on static routing, see Configuring static routes.

Autonomous system number support

An autonomous system (AS) is a single network or a set of networks and routers that are managed and supervised by a common network administrator (or group of administrators) on behalf of a single administrative entity, such as a business division. An AS is assigned a globally unique number that identifies the network to the world. MCR supports both 2-byte and 4-byte autonomous system numbers (ASNs).

ASN support includes per-peer local ASNs.

For more information about how MCR uses ASNs for route advertisement, see MCR Private Cloud Peering.

NAT IP addresses

Network Address Translation (NAT) is generally used for public and private NAT or inter-customer isolation. You can configure NAT for static or dynamic routing.

For more information, see Creating a VXC and How the MCR Performs NAT.