Viewing Traffic Routing through MCRLooking GlassThis topic describes the Megaport Cloud Router (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.

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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 details, 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. MCRs must be

running version 2.0.

To view the Looking Glass

Log in to the Megaport Portal and select Services.

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Choose MCR Looking Glass from the Tools menu. Or, click the

binoculars icon next to an MCR for easy access.

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

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neighbors, the protocols associated with the routes, and more.

MCR Selection – A drop-down list of all provisioned MCRs for an

account.

BGP Sessions – This section includes all BGP sessions configured on

the VXCs for the selected MCR.

Routing 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.

When MCR has more than 20 route table entries, the list is paginated.

You can change how many routes are displayed per page using the

drop-down list at the bottom of the routing table.

The total number of entries in the routing table appears at the top and

the bottom of the routing table.

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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. The BGP Sessions list includes all BGP sessions

running on the Virtual Cross Connects (VXCs) for the selected MCR.

Use this list to find all routes that have been advertised or received from

BGP neighbors.

To search for routes within a BGP session

Type an IP address or text to find matches.

Click Neighbour Routes to open a new tab for that session. The tab

shows the routes advertised towards or received from that peer

BGP router.

Select Advertised or Received to sort the routes.

To sort the table by column

Click the up/down triangles next to a column heading.

The table columns reload, if necessary.

Click the heading again to reverse the order.

A small up or down triangle reflects the current bidirectional sort

order.

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Note

You can open up to five session tabs simultaneously. Adding more than five sessions

replaces the first tab selection with the latest tab selection.

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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 page appears.

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.

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.

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Select All Routes.

After Protocol, select All Types.

The Looking Glass displays all routes. The total number of routes

appears at the top and bottom of the routing table.

To view routes by IP or network address

Select Routes by IP.

Enter an IPv4, IPv6, or network address with an optional subnet

mask. When you enter the address, the control validates it and

displays its format. For example, enter a valid IPv4 address and

IPv4 appears in the control. The Looking Glass searches for all

routes associated with the protocol and displays matching table

entries.

To view routes by protocol

Select All Routes.

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

Select All Routes.

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.

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Note

The Looking Glass searches through the entire routing table, not just the current page

you are viewing.

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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.

Next Hop

VXC

Provides a link to the next hop VXC Connection Details page, so you

can edit the VXC.

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To sort the table by column

Click the up/down triangles 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

Select the BGP Table tab.

Select All Routes.

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To search for BGP Routes by IP address

Select the BGP Table tab.

Select Routes by IP.

Enter an IPv4 or IPv6 network address with an optional subnet

mask. When you enter the address, the control validates it and

displays its format. For example, enter a valid IPv4 address and

IPv4 appears in the control.

The Looking Glass searches for the prefix and displays entries from

the BGP routing table.

To view routes using a text filter

Select All Routes.

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.

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This table describes the column headings and their meaning.

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.

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

Route

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.

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.

Next Hop

VXC

Provides a link to to edit the VXC used to reach the next hop.

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To view BGP route details

Select the down arrow next to a prefix.

This table describes the attributes and their meaning.

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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.

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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

Select the Routes Table tab.

Select All Routes.

For Protocol, select Static.

Reloading the data

Routes are added, updated, and withdrawn from the routing tables as

the networks change.

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The Looking Glass collects route details when you select an MCR and

doesn’t refresh changes to the routes table automatically. The routes

table updates when you manually reload the data.

To reload the route information

Click Reload Data in the upper-right corner.•

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