Skip to content

Viewing Traffic Routing through MCR Looking Glass

This topic describes the Megaport Cloud RouterA managed virtual router service that establishes Layer 3 connectivity on the worldwide Megaport software-defined network (SDN).
(MCR) Looking Glass. The 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.

MCR route selection

MCR uses Border Gateway Protocol (BGP) to exchange network reachability information with adjacent BGP systems, known as neighbors, or peers. During the process of transporting data between BGP neighbors from a source to a destination, MCR makes complex routing decisions about where to send traffic over available routes.

MCR forwards traffic on preferred routes using a combination of metrics received from BGP neighbors and settings on the MCR itself. In addition, MCR follows standard BGP policies and autonomous system (AS) routing best practices. All routes are stored in a routing table. The routing table merges all of the routes from different protocols and connected networks.

What the Looking Glass tells you

The Looking Glass answers questions such as:

  • What route is MCR currently using to send traffic?
  • What are all possible routes MCR can use?
  • What IP prefixes and routes have I received from my BGP neighbor(s)?
  • Which routes have been advertised to my BGP neighbor(s)?
  • Does a route exist in the routing table for a specific destination?

Megaport offers a public API that you can use to access the services available through the Looking Glass. For more information, see Megaport API.

Viewing the Looking Glass

The routing table information is available through the Looking Glass only after you have provisioned one or more MCRs.

To view the Looking Glass

  1. Log in to the Megaport ONE Portal.
  2. Choose Tools > MCR Looking Glass. Select MCR
  3. Select an MCR from the drop-down menu.
    Only MCRs with a Live provisioning status are shown.

Tip

You can also view the Looking Glass for a specific MCR by selecting the Gear icon (Gear icon) > MCR Looking Glass for the MCR from the Access page. For details, see Viewing Network Services.

The Looking Glass displays the routing table entries along with the path MCR uses to arrive at a destination, the VXCs that connect the BGP neighbors, the protocols associated with the routes, and more. MCR Looking Glass

  • Select an MCR – A drop-down list of all MCRs with a Live provisioning status.

  • MCR BGP Sessions – This section includes all BGP sessions configured on the VXCs for the selected MCR.

  • Routes Table – This table provides the big picture by displaying all of the networks that MCR can reach, including static, local, connected, and BGP routes. MCR consults this table when selecting the best route for forwarding traffic to a destination.

  • BGP Table – This table includes all BGP sessions running on the Virtual Cross Connects (VXCs) for the selected MCR.

When MCR has more than 100 table entries, the list is paginated.

The total number of entries in the routing table appear at the bottom of the routing table, along with the number of displayed routes.

BGP sessions

BGP communicates between two neighbors using a standard TCP connection. Once connected, the BGP neighbors share routing information with each other. The connection between the neighbors is called a BGP session.

Use this table to find all routes that have been advertised or received from BGP neighbors.

To search for routes within a BGP session

  • In the Search field, type an IP address or text to find matches.

To sort the table by column

  • Click the up or down triangle next to a column heading.
    The table columns reload, if necessary.
  • Click the heading again to reverse the order.
    A bold up or down triangle reflects the current bidirectional sort order.

VXC details

Status icons indicate the current BGP session status:

  • A green check mark means that the session is up.
  • A red x means that the session is down.
  • A yellow information icon means that the session status is unknown.

To view or edit a VXC

  • Click the VXC name.
    The connection details appear.

Routing table

The routing table includes all of the networks that MCR can reach, along with the path MCR uses to arrive at a destination.

When MCR receives a packet, it examines the packet’s destination IP address and uses the routing table to make forwarding decisions accordingly. For example, suppose MCR is selecting a route for a packet with a destination IP address of 10.0.0.3. MCR consults the routing table and considers 10.0.0.0/8 and 10.0.0.0/24 as candidates because they both cover the address range. In this example, MCR would select 10.0.0.0/24 as the best match, because it is the most specific.

Note

Click any address in the table to copy it to the clipboard.

Searching the routing table

This section describes several ways to retrieve detailed information about routes.

To view the routing table

  • Select the Routes Table tab.

    The Looking Glass displays all routes. The total number of routes appear at the bottom of the routing table.

To view routes by IP or network address

  • In the Search field, enter an IPv4, IPv6, or network address with an optional subnet mask.

The Looking Glass searches for all routes associated with the address and displays matching table entries.

Note

The Looking Glass searches through the entire routing table, not just the current page you are viewing.

To view routes by protocol

  • Select the Routes Table tab.
  • Select a protocol.
    The Looking Glass searches for all routes associated with the protocol and displays matching table entries.

To view routes using a text filter

  1. Select All Routes.
  2. Enter text, one search term at a time. For example, type Azure or 20.
    The Looking Glass filters the table based on the search term and displays matching table entries.

This table describes the column headings and their meaning.

Heading Description
Prefix Displays the destination network of the route. An IP network is a group of IP addresses. The network address is the prefix.
For example:

IPv4 address: 192.0.2.1
IPv4 network prefix: 192.0.2.0/24 (includes 192.0.2.0 - 192.0.2.255)
Metric Displays the route’s local preference.
Protocol Connected - Indicates the route was learned as a result of configuring the interface and is directly connected to the interface.

Static - Indicates the route was explicitly configured as a static route.

BGP - Indicates the route was received through BGP update messages from a BGP neighbor.

Local - Indicates the route is local to MCR.
Distance Displays the administrative distance assigned to the route. This value can be used during selection of the best route when there are two different routes to the same destination from two different routing protocols. The smaller the administrative distance, the higher the preference.
Next Hop Displays the IP address of an adjacent router, or hop, in the remote network that tells MCR where to send the packet.

An IP address of 0.0.0.0 indicates the route is local to MCR and MCR doesn’t need a next hop address to route the traffic to its destination.

To sort the table by column

  • Click the up or down triangle next to a column heading.
    The table columns reload, if necessary.
  • Click the triangle in the heading again to reverse the order.
    The triangle reflects the current bidirectional sort order.

Viewing BGP routes

A BGP route is a destination consisting of an IP address prefix and other details describing the path to the destination. The BGP table page displays the BGP table that summarizes all BGP routes (not only the best routes) from all of the BGP neighbors, including several routes to the same network with different attributes.

To view the BGP table

  1. Select the BGP Table tab.
  2. From the Show drop-down menu, select All Routes.

BGP Route Table

Note

Click any address in the table to copy it to the clipboard.

To advertised or received routes to or from a VXC

  1. Select the BGP Table tab.
  2. From the Show drop-down menu, select Advertised Routes or Received Routes.
  3. Select the originating IP address or VXC name used to reach the next hop.

To search for BGP Routes by IP address

  1. Select the BGP Table tab.
  2. In the Search field, enter an IPv4, IPv6, or network address with an optional subnet mask.

    The Looking Glass searches for the prefix and displays entries from the BGP routing table.

To view routes using a text filter

  1. Select All Routes.
  2. Enter text, one search term at a time. For example, type AWS or 20.
    The Looking Glass filters the table based on the search term and displays matching table entries.

To view the next hop VXC

  1. Select All Routes.
  2. Enter text, one search term at a time. For example, type AWS or 20.
    The Looking Glass filters the table based on the search term and displays matching table entries.

This table describes the column headings and their meaning.

Heading Description
Prefix Displays the destination network of the route. An IP network is a group of IP addresses. The network address is the prefix.
For example:

IPv4 address: 192.0.2.1
IPv4 network prefix: 192.0.2.0/24 (includes 192.0.2.0 - 192.0.2.255)

Click the Copy icon to copy the prefix to the clipboard.
Best For each prefix in the routing table, when there are two or more next-hop routers advertising a path to that destination network, MCR selects the preferred route. MCR uses the metrics and distance values from the received route advertisements to determine the best route to a destination.

A check mark indicates that MCR considers this route to be the best when choosing between two routes to the same destination.

An X indicates that MCR does not prefer this route when choosing between two routes to the same destination.
Last Updated Displays the last time the route was updated.
Next Hop Displays the IP address of this particular hop in the remote network.
A blank space indicates that this route is Local or Connected and doesn’t need another router to reach it.

BGP route details

BGP routes have several associated attributes that MCR can consider to select the best route. Looking Glass retrieves the values for the BGP attributes directly from MCR. They can either be values that MCR has received, or they can be values that MCR has set.

To view BGP route details

  • Select the arrow next to a prefix.

BGP route details

Note

Click any address in the table to copy it to the clipboard.

This table describes the attributes and their meaning.

Attribute Description
AS path Displays a list of all autonomous system numbers (ASNs) through which the route has passed.
For example:

132863 58941 58941 4826

Each ASN identifies an individual BGP network.

Shorter AS paths are preferred because a shorter path can indicate a closer destination.
Local Preference Displays the preference used within an autonomous system. The highest local preference is preferred. The default value is 100.
Multi-Exit Discriminator Displays the Multi-Exit Discriminator (MED) value that is considered while selecting the preferred traffic route.

MCR considers the MED when the advertising AS path is the same for candidate routes and there are multiple entry points for that AS. To determine the preferred VXC, MCR selects a lower MED metric over a higher metric.

For details on setting the MED, see Configuring a preferred route.
Origin Indicates where a prefix came from. A prefix origin is a key factor used by BGP to select the best path to a destination between multiple alternative paths in the network. The lowest value is preferred.

IGP - Indicates that the prefix originated from an Interior Gateway Protocol. This origin has the lowest and most preferred value.

EGP - Indicates that the prefix originated from an Exterior Gateway Protocol. This origin has the medium value.

Incomplete - Indicates that the prefix was learned via other means, such as statically defined. This origin has the highest value.
Communities Displays the route’s BGP community. BGP communities are a group of destinations that share a common property. The format is:

As-number:community-value

For example, 65534:100.

Note: BGP sessions on MCR transparently pass standard and extended BGP communities between neighbors. However, MCR reserves some private ASNs for internal use. When MCR receives a BGP community that is in use internally, it will strip the community from the BGP session. To prevent BGP community removal, avoid communities defined with a 2-byte private ASN as their first value. For example, private_asn:nnn.
Weight A local attribute used to set path priority when multiple paths exist out of a Cisco router for a destination. Higher weights are the priority.

Viewing static routes

Static routes are manually defined and maintained. Static routing is not really a routing protocol but instead a simple process of manually entering a route prefix and destination to define a route.

To view static routes

  1. Select the Routes Table tab.
  2. For Protocol, select Static.

Refreshing the data

Routes and BGP sessions are added, updated, and withdrawn from the Looking Glass as the networks change.

The Looking Glass collects route and BGP session details when you select an MCR and doesn’t refresh changes automatically. The display updates when you manually refresh the data.

To refresh the route or BGP session information

  • Click the Refresh button.

BGP Session Refresh

Downloading routes

The Looking Glass provides a convenient way to download all routes associated with an MCR. You can save the routes in either the command-separated values (CSV) format or the JavaScript Object Notation (JSON) format.

To download a list of routes

  1. In the Looking Glass, select a routes table tab and click Export Routes.

  2. Select a file format.

Export Routes from Looking Glass

The Looking Glass saves the route list in the selected file format and downloads the file to your Downloads folder.


Last update: 2023-01-26