What is the maximum limit of domains in a DNS search list?
Environment
- RHEL 5
- RHEL 6
- glibc package versions lower than glibc-2.17-222.el7
Issue
-
Need more than 6 domains in the resolv.conf search list.
-
Only the first 6 domains in the search path are looked up by the resolver.
Resolution
Upgrade glibc packages to versions be at or above glibc-2.17-222.el7.
Root Cause
The search list is currently limited to six domains with a total of 256 characters.
The limit is specified by glibc source at resolv/resolv.h as below:
# define MAXDNSRCH 6 /* max # domains in search path */
This cannot be modified for RHEL 6.x and below and is resolved in RHEL7 glibc package versions at or exceeding glibc-2.17-222.el7.
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