Advanced - SIP/RTP (Tab) - SIP(Section)__SIP Dirty Host TTL (s)
Specify the “Time to Live” (TTL) for dirty hosts in seconds. This means that, when a phone was unable to reach a host, the phone will not try to reach this host again until the time speciﬁed in this ﬁeld has elapsed.
If this setting is 0 or empty, it has no effect (the host is set as "dirty" but only for 0 seconds, which means it will have no effect on future requests)
See also: sip_request_timeout, sip_retry_t1, sip_health_check
Integer values, e.g. <60>, <120>.