Troubleshooting IX With a BGP Session Routing Issue

When a session on Internet Exchange (IX) is experiencing a routing issue, step through these troubleshooting actions.

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 authentication	Look through the logs for `Invalid MD5 digest`. Verify that the correct BGP MD5 password is in use for the and of the VXC.
Run connectivity tests	Run a test between the A-End 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?

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 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
logs between source and destination host
Packet capture logs, if possible (file size can be up to 10 M)

​Troubleshooting actions

​Next steps

​Collect essential troubleshooting data

Troubleshooting actions

Next steps

Collect essential troubleshooting data