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How do you determine the most specific network route ONTAP 9.2 and later versions will use for network traffic?

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Applies to

  • ONTAP 9.2 and later versions
  • IPv4

Description

  • How ONTAP chooses a route when it needs to initiate a new request or reply to a request.
  • To determine the most specific route(s) to the destination, run the following command from the ONTAP CLI:​​​​​​
    • set advanced; network route active-entry show -vserver vserver -node node-01 
    • This will include routes that originate from the LIFs on the node specified
      • The command "route show" will only show routing configurations (not the actual routes in the routing table)
    • Alternatively, ROUTE-ACTIVE.XML can be reviewed in the AutoSupport section of  ActiveIQ 
  • From the available routes determine which route has the "narrowest" (most-specific or smallest) subnet that the destination IP will fit into.
    • For example, if the destination IP address is 10.1.1.1, looking at routing table with the following destinations:
      • "default" or 0.0.0.0/0 matches and has a /0 (all zeroes) netmask
      • 10.1/16 matches and has a /16 (255.255.0.0) netmask
      • 10.1.1/24 matches and has a /24 (255.255.255.0) netmask
      • 10.1.1.1/32 matches and has a /32 (all ones) netmask (32 is more specific than 24, 16, and 0). This is an example of a single host route, an exact match to a single IP address, making it the most specific route

(The actual routing decision takes place looking at most-specific to least-specific address, ending up a the default route 0.0.0.0/0 when nothing else matches, including link-local addresses.

Additional Information

 

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