Bug ID 560510: Invalid /etc/resolv.conf when more than one DNS servers are set and MCPD is down.

Last Modified: Jul 18, 2026

Affected Product(s):
BIG-IP LTM, MA-VE(all modules)

Known Affected Versions:
11.5.1, 11.5.1 hf1, 11.5.1 hf2, 11.5.1 hf3, 11.5.1 hf4, 11.5.1 hf5, 11.5.1 hf6, 11.5.1 hf7, 11.5.1 hf8, 11.5.1 hf9, 11.5.1 hf10, 11.5.1 hf11, 11.5.2, 11.5.2 hf1, 11.5.3, 11.5.3 hf1, 11.5.3 hf2, 11.5.4, 11.5.4 hf1, 11.5.4 hf2, 11.5.4 hf3, 11.5.4 hf4, 11.5.5, 11.5.6, 11.5.7, 11.5.8, 11.5.9, 11.5.10, 11.6.0, 11.6.0 hf1, 11.6.0 hf2, 11.6.0 hf3, 11.6.0 hf4, 11.6.0 hf5, 11.6.0 hf6, 11.6.0 hf7, 11.6.0 hf8, 11.6.1, 11.6.1 hf1, 11.6.1 hf2, 11.6.2, 11.6.2 hf1, 11.6.3, 11.6.3.1, 11.6.3.2, 11.6.3.3, 11.6.3.4, 11.6.4, 11.6.5, 11.6.5.1, 11.6.5.2, 11.6.5.3, 12.0.0, 12.0.0 hf1, 12.0.0 hf2, 12.0.0 hf3, 12.0.0 hf4

Fixed In:
12.1.0

Opened: Dec 02, 2015

Severity: 3-Major

Symptoms

When MCPD is not in the running state, dhclient directly writes domain-name-server information into /etc/resolv.conf. If multiple domain-name-servers are given by DHCP server, they are written in the incorrect format with multiple domain-name-servers in a single line comma-separated. Each domain-name-servers entry should be written in a single line with "nameserver" prefix.

Impact

Domain name resolution doesn't work.

Conditions

- MCPD is not in the running state. - DHCP is enabled. - DHCP server has provided multiple domain-name-server entries in the lease.

Workaround

Bring up MCPD which would write the resolv.conf in the correct format. Alternatively, user can manually modify /etc/resolv.conf to write multiple nameserver entry one per line.

Fix Information

DHCP will now write a single nameserver per line in /etc/resolv.conf when multiple nameservers are configured in DHCP.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips