Troubleshooting MCR When a BGP Session is Down
When a BGP session on Megaport Cloud Router (MCR) is down, step through these troubleshooting actions.
|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.
|Verify the route filtering||The MCR Looking Glass displays the routes received or sent after applying route filtering. For details, go to Viewing Traffic Routing Through MCR Looking Glass.
|Check the BGP neighbor state||When BGP is configured with a neighbor IP address, 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:
|Verify the MD5 authentication||
|Run connectivity tests||
|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
If the troubleshooting actions do not resolve your issue, contact support. Before contacting support for assistance, collect the following information.
- 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?
Collect the following required data
BGP configuration information:
- Interface settings, including VLAN 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 any
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)
- Traceroute logs between source and destination host
- Packet capture logs, if possible (file size can be up to 10 M)