Slow access to certain web sites after upgrading to SGOS 5

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Technical Alert

Affected Products

ProxySG SGOS 5.5.x.x


Beginning with SGOS 5.5.x.x, the ProxySG performs IPv4 and IPv6 DNS queries. Because not every DNS server is configured to answer to IPv6 queries, this can cause a delay since the ProxySG waits for an answer to the IPv6 query.


Issue is resolved in SGOS


The issue is resolved in SGOS  Please see bug 139106 in the release notes.  SGOS and accompanying release notes can be downloaded from .  For information on how to upgrade SGOS, please see 000014861 titled "How do I upgrade SGOS on my ProxySG?".


If you do not wish to upgrade SGOS, you can work around the issue by adding the following CPL code to the Local Policy File.  This code prevents the ProxySG from performing IPv6 DNS queries and, in most cases, fixes the slowness issue.



For information on how to install CPL into the local policy file, please see 000010101.

Bug Number

Two bugs are mentioned here:

  • 139106 When DNS lookups are configured to use "Prefer IPv4 over IPv6", ProxySG still waits for IPv6 DNS lookups to complete before HTTP requests are sent out.
  • 140690 Switching Off AAAA lookups not working as expected  <--  This looks like it might be a duplicate of 139106.  Bug status is WORKSFORME.
InQuira Doc IdTFA39

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First Published      10/01/2014
Last Modified      10/01/2014
Last Published      10/01/2014
Article Audience
Product      ProxySG
Software      SGOS 5.5
Topic      Upgrade / Maintenance, Usability
Article Number      000007632
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