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We have been experiencing slow timeouts for unreachable hosts is extremely slow. Recent testing in our lab shows it may be a delay reporting negative ARP lookups. Dumping traffic during attempts to open a telnet connection to a local zone which was down for patching showed the following.

If the source was Linux three ARP requests were sent at 1 second intervals, and the connection failed in just over three seconds.

If the source was a Solaris server an initial five ARP requests were sent to the broadcast address at 1 second intervales. 5 seconds later more ARP requests were sent. ARP requests continued with increasing pause times until the connection failed after 3 minutes and 44 seconds. Tests were run from a global zone to a local zone on a different global. Both global zones are running on Sparc hardware. The devices are connected via level 2 switching equipment.

Are there any tunables which will result in a fast (3 to 5 seconds) ARP failure? Are there any other tunables which will cause connections to unreachable (downed) hosts to fail faster?

We appear to have the same or similar behavior between a variety of servers running on Sparc. As far as I can tell, Solaris is trying very hard get an address by ARPing the address, and does not time out very quickly if no host is replying to the ARP request.

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  • If you snoop on another machine, do you actually see the arp-whois messages on the Ethernet Broadcast address? Also what I don't understand: You tried to connect from a local zone to another zone on the machine, did I get this correctly? Also, which architecture? SPARC or Intel?
    – Alexander Janssen
    Oct 5, 2012 at 16:10
  • @AlexanderJanssen I have updated the post with additional information.
    – BillThor
    Oct 9, 2012 at 0:31
  • So SPARC then, eh? Is local-mac-address set to true? If it's not, the same MAC-address from a multiport ethernet card might be visible on more then just one port. This can confuse the switch. Refer to docs.oracle.com/cd/E19963-01/html/821-1458/geyqe.html
    – Alexander Janssen
    Oct 9, 2012 at 19:30
  • @AlexanderJanssen The server is down, so no ARP responses are expected nor generated. Solaris keeps ARPing for several minutes before reporting the server is unreachable.
    – BillThor
    Oct 9, 2012 at 23:06

1 Answer 1

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Did you consider running ndd /dev/arp \? to see a list of ARP related kernel configurables?

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  • Yes, we had checked all values, and did not find any values that would explain the behavior. Based on the arp_probe_count value of 3 we would expect behavior similar to what we experience with other operating systems.
    – BillThor
    Oct 9, 2012 at 23:19

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