Details for VCN Flow Logs
This topic provides details for VCN Flow logs.
|API value (ID):||Console (Display Name)||Description|
|all||Flow Logs (All records)||Includes both accept and reject records in VCN flow logs.|
VCN Flow Logs are available in all the regions of the commercial realm.
Each instance in a VCN has one or more virtual network interface cards (VNICs). The Networking service uses security rules to determine what traffic is allowed through a given VNIC. Security rules can be defined using Security lists or Network security groups.
To help troubleshoot the traffic in and out of your VNICs, you can set up VCN flow logs. Flow logs record details about traffic that has been accepted or rejected based on the security rules set up for your VCN.
You can enable flow logs for a given subnet, which means traffic is logged for all existing and future VNICs in that subnet. Each flow log contains information about traffic for a single VNIC.
Certain traffic to core Oracle infrastructure services hosted on link-local (169.254.0.0/16) IP addresses do not appear in flow logs. This includes items such as VCN DNS, DHCP and block storage. Also excluded is network management traffic, such as ARP.
Contents of a VCN Flow Log
A flow log record contains the following fields:
Type of record. Possible values:
|data.bytesOut||Number of bytes recorded in the capture window.||17114|
IP address of the destination, either in IPv4 dot, or IPv6 colon notation.
When IPv6 traffic is encountered in a customer's virtual cloud network, a flow log entry with IPV6 address values is generated, in place of the current location of IPV4 values. The source and destination addresses could be either IPv4 or IPv6, based on the configuration and traffic present in the customer’s VCN. This data will only be available in regions where IPv6 support is generally available and configured by the customer.
|data.destinationPort||IANA port number of the destination.||36266|
|data.endTime||End time of the capture window in Unix epoch seconds.||1598917970|
|data.flowid||Hash of key fields (source and destination addresses, ports, and protocol).||a6a73770|
|data.packets||Number of packets recorded in the capture window.||250|
|data.protocol||IANA protocol number.||6|
|data.protocolName||IANA name for protocol.||TCP|
IP address of the source, either in IPv4 dot, or IPv6 colon notation.
See the note in the data.destinationAddress description.
|data.sourcePort||IANA port number of the source.||443|
Start time of the capture window in Unix epoch seconds.
Unix epoch time uses a fixed point in the past to reference the current time. That means that every second of the current time can be expressed as a number, such as 1576090259 (which is Wednesday, December 11, 2019 6:50:59 PM GMT).
Each flow log record records a one minute interval (0 - 59 seconds) of data flow, using epoch start and end times to indicate the time that data appears during the 60 second interval for that record. Let's consider the epoch time entries that would appear for data flow during a fixed interval of 140 seconds. At five seconds past a particular minute, you open a connection to your host and begin to continuously send data over that connection for the next 140 seconds (< three minutes, three records).
This is how the epoch start and end times would appear in the log:
Status of data capture window. Possible values:
|data.version||Version of the flow log record schema.||2|
|datetime||Timestamp in milliseconds. Same as the oracle.ingestedtime field but in milliseconds.||1598917955000|
|id||Random UUID, unique to each log entry.||abcdabcd-abcd-abcd-abcd-abcdabcdabcd|
|oracle.compartmentid||OCID of the compartment the log group is in.||ocid1.compartment.oc1.<region-id>.<unique-id>|
|oracle.ingestedtime||Time the log was ingested by OCI Logging.||2020-08-31T23:53:54Z|
|oracle.loggroupid||OCID of the log group.||ocid1.loggroup.oc1.<region-id>.<unique-id>|
|oracle.logid||OCID of the log.||ocid1.log.oc1.<region-id>.<unique-id>|
|oracle.tenantid||OCID of the tenant.||ocid1.tenancy.oc1..<region-id>.<unique-id>|
|oracle.vniccompartmentocid||OCID of the compartment to which the VNIC belongs.||ocid1.compartment.oc1..<region-id>.<unique-id>|
|oracle.vnicocid||OCID of the VNIC.||ocid1.vnic.oc1.<region-id>.<unique-id>|
|oracle.vnicsubnetocid||OCID of the subnet to which the VNIC belongs.||ocid1.subnet.oc1.<region-id>.<unique-id>|
|specversion||OCI logging schema version.||1.0|
|time||Same as startTime.||2020-08-31T23:52:35Z|
|type||Category of log: DataEvent, QualityEvent.NoData, or QualityEvent.SkipData.||com.oraclecloud.vcn.flowlogs.DataEvent|
Limitations and Considerations
- Some traffic may not be logged during a capture window because of capacity issues or system errors. In such cases, NODATA or SKIPDATA log status is recorded.
- Some services manage VNICs. For example, the Load Balancing service manages VNICs attached to load balancers. Flow logs for managed VNICs are captured, and identified by VNIC ID. Flow logs, however, currently do not include a field to indicate what service such VNICs belong to.
- For traffic over the public IP of a Compute instance, flow logs records the corresponding private IP.
Using the Command Line Interface (CLI)
See VCN Flow Logs Example for example commands.