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Router Configuration

This article covers the following topics related to the configuration of routers, switches, etc. to collect and export flow records (NetFlow, IPFIX, sFlow) and other network data (BGP, SNMP) to Kentik Detect:

Notes:
- Model-specific configuration settings for sending flow records to Kentik Detect are provided in Router Flow Configs.
- Model-specific configuration settings for BGP peering with Kentik Detect are provided in Router BGP Configs.
- To learn how to register routers on the Kentik system see Device Settings.
- For general information about flow, see Flow Overview.
- For information about host configuration, see Host Configuration.
- As used in this Knowledge Base, the term “router” refers as well to other non-host network devices such as switches.

 

 
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Router Configuration Overview

Setting up a router to use with Kentik Detect involves configuration steps on the device itself and also in the Kentik Detect portal using the Add Device dialog (accessed via Admin » Devices; see Device Admin Dialogs). Before you start, you’ll need to know whether you’ll be exporting flow data to the Kentik Detect servers directly or through a local encryptor/redirector running the Kentik software called “chfagent” (see NetFlow Proxy Agent).

The device configuration process varies depending on device manufacturer, but is typically performed in “configuration mode” or in a “configuration editor.” Before you start you’ll need to know the following information:

  • IP and port: The destination IP and Port to which the router should send flow data:
    - If the flow data is to be sent directly to Kentik Detect, this information (which varies from customer to customer) is found in the General Settings tab of the Add Device dialog in the Kentik Detect portal (see Device Config Info).
    - If the flow data is to be encrypted by chfagent before being sent to Kentik Detect, these values will be the IP and Port you chose on your local encryptor/redirector running chfagent.
  • Sample rate: The sample rate at which you want to sample flow records (see Flow Sampling). The rate configured on the router should match the rate set for the same device in the Kentik Detect portal (see Device General Settings).
  • Ingress or egress: Whether you will examine traffic at ingress or egress (ingress is recommended; see Ingress and Egress).

Once you’ve gathered the information listed above you’re ready to configure your routers to work with Kentik Detect. Configurations that work on some specific hardware/software combinations are covered in the following KB articles:

  • Configuration settings for sending flow records to Kentik Detect (required) are provided in Router Flow Configs.
  • Configuration settings for BGP peering with Kentik Detect (available only for devices on plans that include BGP; see About Plans) are provided in Router BGP Configs.

 

 
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Router Troubleshooting

If you’ve configured a router to send flow to Kentik Detect (using the router-specific configurations provided in Router Flow Configs) and you are not seeing flow from that router in the Kentik Detect portal, then we’ll need to know if the router is able to ping our collectors reliably with large packets. To find that out, please perform the following simple tests:

  • Determine that there’s no loss between your server and Kentik Detect:

ping -c200 -D -s400 flow.kentik.com

  • Determine if the MTU between you and Kentik Detect is “normal”:

ping -c100 -D -s1472 flow.kentik.com

  • Determine if fragmentation works either way:

ping -c100 -s1500 flow.kentik.com

The information that you gather from these tests will help us troubleshoot the issue if you contact support@kentik.com.

 

 
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SNMP OID Polling

SNMP polling by Kentik Detect is covered in the following topics:

 

 
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About SNMP Polling

OIDs are identifiers for SNMP objects that each represent the properties of a network-connected device such as a router. An OID takes the form of a path to the SNMP object it represents. Like a standard HTTP path, each segment represents a successively narrower slice of the entire networked universe, but in the case of an OID each segment is a pre-assigned number. The base OID for MIB-2 defined SNMP variables is 1.3.6.1.2.1.

Kentik Detect polls SNMP OIDs in two different categories (see details in table below):

  • Selected counter OIDs
  • Selected info OIDs

Note: SNMP is polled on a given device only when Kentik Detect is actively receiving flow from that device.

 

 
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SNMP Polling Intervals

The polling intervals for a given router depend on the device’s SNMP Polling setting, which is set in the Add Device or Edit Device page (see Device IP & SNMP Settings):

  • If Standard, interface counter will be polled every 10 minutes and interface description every 3 hours.
  • If Minimum, interface counter won’t be polled and interface description will be polled every 6 hours.

Note: The Interface List (see Interfaces Page) includes indicators that enable you to compare flow volume as reported via SNMP polling with flow volume as reported in flow records from the same device.

 

 
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Enabling SNMP Polling

To enable Kentik Detect to properly poll SNMP on a given router:

  • Determine which version of SNMP to use (see About SNMP V3).
  • Ensure that SNMP is enabled for the router (consult documentation for your router make and model).
  • Permit SNMP polling of the router from the IPs listed in the Device SNMP Polling IPs field of the Device Details page in the portal.
  • Set community on the router to match the SNMP Community string indicated on the Device Details page for the router.
  • If the router has been configured to block polling of any of the specific OIDs polled by Kentik Detect, re-enable polling of those OIDs.

 

About SNMP V3

Kentik Detect supports polling via SNMP V3, which is more secure than previous SNMP versions. SNMP V3 is recommended for customers who have concerns about using SNMP V2 over the public Internet.

The SNMP V3 implementation in Kentik Detect allows each of the following to be enabled and configured independently:

  • Authentication: Options include:
    - None
    - MD5
    - SHA
  • Privacy: The actual encryption of SNMP transactions:
    - None
    - 56-bit DES encryption
    - AES

Note: Kentik Detect’s SNMP V3 privacy options do not currently include 168-bit 3DES.

To use SNMP V3:

  1. Configure your router to enable polling via SNMP V3. Consult your router documentation for the correct settings.
  2. Using the SNMP V3 toggle switch on the Add Device or Edit Device page in the Kentik Detect portal, enable SNMP V3 and fill in the resulting additional fields (see Device IP & SNMP Settings).

 

 
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Verifying SNMP Polling

If you’ve successfully completed the steps in Enabling SNMP Polling, after about 10 minutes (one complete counter polling interval) you’ll be able to verify in the portal that Kentik Detect is able to poll your router:

  • Go to the portal’s Devices page (choose Devices from the drop-down Admin menu).
  • In the Device list, confirm that the SNMP indicator in the column at left is green.
  • Click the Interfaces button for the router, which takes you to that router’s Interfaces page.
  • Verify that names and descriptions for the router’s interfaces appear on the Interfaces page.
  • Verify that blue bars for SNMP ingress and egress are present in the left-hand columns of the Interfaces list.
  • Click the Traffic button to go to the Data Explorer, where you’ll see a graph comparing SNMP and flow rates for the router over the preceding hour.

 

 
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Kentik-polled SNMP OIDs

The OIDs polled by Kentik Detect are shown in the following table:

OID (1.3.6.1.2.1...) Object/variable name
(SNMP_...)
Standard polling interval Minimized polling interval Description
...31.1.1.1.6 ifHCInOctets 10 min N.A. Counter: The total number of octets received on the interface, including framing characters.
...31.1.1.1.7 ifHCInUcastPkts 10 min N.A. Counter: The number of packets, delivered by this sub-layer to a higher (sub-)layer, which were not addressed to a multicast or broadcast address at this sub-layer.
...31.1.1.1.10 ifHCOutOctets 10 min N.A. Counter: The total number of octets transmitted out of the interface, including framing characters.
...31.1.1.1.11 ifHCOutUcastPkts 10 min N.A. Counter: The total number of packets that higher-level protocols requested be transmitted, and which were not addressed to a multicast or broadcast address at this sub-layer, including those that were discarded or not sent.
...2.2.1.2 ifDescr 3 hrs 6 hrs Info: A textual string containing information about the interface. Includes manufacturer name, product name, and interface version.
...31.1.1.1.18 ifAlias 3 hrs 6 hrs Info: An ‘alias’ name for the interface, as specified by a network manager, that provides a non-volatile ‘handle’ for the interface.
...31.1.1.1.15 ifHighSpeed 3 hrs 6 hrs Info: An estimate of the interface’s current bandwidth in bits per second.
...4.20.1.2 ipAdEntIfIndex 3 hrs 6 hrs Info: An index value that uniquely identifies an interface.
...4.20.1.3 ipAdEntNetMask 3 hrs 6 hrs Info: The subnet mask associated with the IP address of this entry.
...55.1.8.1.2 ipv6AddrPfxLength 3 hrs 6 hrs Info: The length of the prefix (in bits) associated with the IPv6 address of this entry.
...1.1 sysDescr 3 hrs 6 hrs Info: A textual description of the entity. Includes the full name and version identification of the system’s hardware type, software operating-system, and networking software.

Notes:
- Discontinuities in the value of counters can occur at re-initialization of the management system, and at other times as indicated by the value of the OID ifCounterDiscontinuityTime (1.3.6.1.2.1.31.1.1.1.19).
- Additional information about the above OIDs may be found in the OID Repository at http://oid-info.com/.

 

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