Troubleshooting IX With a BGP Session Routing Issue

When a BGPBorder Gateway Protocol (BGP) is a standardized routing protocol designed to exchange route and reachability information among autonomous systems (AS) on the internet.
session on Internet Exchange (IX) is experiencing a routing issue, step through these troubleshooting actions.

Tip

Megaport operates a public, web-accessible MegaIX Looking Glass for peers and network operators to investigate the current routing state. You can query the primary and redundant route servers for live BGP data here: MegaIX Looking Glass.

Troubleshooting actions

Action	Steps
Verify the BGP configuration	Check the ASN, BGP IP address, and subnet mask.
Verify access to TCP port 179	BGP neighbors establish a TCP session using TCP port 179. Make sure that a BGP neighbor is not blocking ingress or egress from TCP port 179 and other relevant ephemeral ports. You can view the port number using Wireshark, the debug ip packet detail command, or netstat in Windows. Make sure that all firewalls and ACLs permit TCP port 179 in both directions.
Check the BGP neighbor state	When BGP is configured with a neighbor IP address (route servers, bilateral peers, or both), it goes through several stages before it reaches the Established state. The BGP Neighbor States are Idle, Connect, Active, OpenSent, OpenConfirm, and Established.
Check the BGP message type	BGP packets use these message types: OPEN – Sets up and establishes BGP adjacency. UPDATE – Advertises, updates, or withdraws routes. KEEPALIVE – Ensures that the BGP neighbor is still alive. NOTIFICATION – Indicates an error condition to a BGP neighbor.
Verify the MD5Sometimes known as an MD5 hash or BGP key. The message-digest (MD5) algorithm is a widely used cryptographic function producing a string of 32 hexadecimal digits. This is used as a password or key between routers exchanging BGP information. authentication	Look through the logs for `Invalid MD5 digest`. Verify that the correct BGP MD5 password is in use for the A-EndThe start of the connection – the Port, MCR, or MVE. Megaport connections need an A-End and a B-End. The connection starts with an A-End. Most often, the Port is the A-End. The B-End is the other end of the connection: it can be a Port, an Internet Exchange, a Marketplace connection, or a cloud service provider. and B-EndA Port, MCR, or MVE establishes the A-End of the connection and the B-End is the other end. The B-End can be a Port, MCR, or MVE for a private VXC, an Internet Exchange, a Marketplace connection, or a Cloud Service Provider (CSP). of the VXC.
Run connectivity tests	Run a pingA ping test transmits data packets to a specific IP address and either confirms or denies connectivity between IP-networked devices. test between the A-End PE routerA router between one network service provider’s area and areas administered by other network providers. and the B-End PE routers that are connected to route servers to test multilateral peering. Run a ping test between the A-End PE router and the B-End PE router that is connected to bilateral peer to test the bilateral peering. Ask the customer run a ping test from their BGP router to the BGP neighbor IP addresses to test end-to-end connectivity. Confirm the ARP table entry of the BGP peer.
Find error conditions in BGP logs	The BGP protocol sends a notification message when it detects an error with the BGP session such as an expiring hold timer, a change to neighbor capabilities, or a request to reset a BGP session. When an error is detected, the BGP session is closed. For example, enter show log %BGP-xxxxx. For more information, see Internet Exchange Overview.

Next steps

If the troubleshooting actions do not resolve your issue, contact support. Before contacting support for assistance, collect the following information:

All troubleshooting steps taken, in detail. For example, if you place loopbacks, note their location and direction.
Note the date, time, and time zone in which the issue started.
Is the BGP session down?
Is the BGP session flapping? For example, does the peering establish, then drop, re-establish and then drop? Try to pinpoint where the problem might be in the network using ping.
Is there a BGP routing issue?

Note

For more information about when a field service technician is needed onsite at the data center, see Customer Field Services.

Collect essential troubleshooting data

BGP configuration information

Interface settings, including VLANA partitioned and isolated computer network at the data link layer (OSI Layer 2) on a single physical interface (for example, a Port) used to subdivide a network. LAN is an abbreviation of local area network.
number
BGP IP address and subnet mask
BGP ASN
BGP network addresses to be advertised
BGP neighbor IP address and subnet mask
BGP neighbor ASN
BGP neighbor network addresses to be received
BGP authentication between BGP peers
BGP route filtering and manipulation (if applicable)

BGP command output and packet capture information

Examine the BGP neighbor table and BGP state using the show IP BGP summary command
Examine the BGP neighbor details using the show IP BGP neighbors command
Logs that show BGP-related messages (output from the show log %BGP-xxxxx command)
BGP routing table entries that have BGP routing issues (output from the show IP BGP command)
BGP advertised routes (output from the show IP BGP neighbors <neighbor-ip-address> advertised-routes command)
BGP received routes (output from the show IP BGP neighbors <neighbor-ip-address> routes command)
Routing table (output from the show IP route <ip-address> command) at both ends
TracerouteA diagnostic tool that examines how data moves through the internet to determine if a destination is reachable.
logs between source and destination host
Packet capture logs, if possible (file size can be up to 10 M)