To all the crazy ones, all the gurus: TLDR: FreeSWITCH Server looses connectivity with main router (gateway), can ping any other server but cannot reach router. We have a cluster of FreeSWITCH servers running behind Kamailio. For 3 years we have been up and running smoothly without any glitches. Last week we upgraded our FreeSWITCH servers, the upgrade included: 1) Upgraded Debian Squeeze to Ubuntu LTS 14.04 2) Upgraded FreeSWITCH from version 1.2 to 1.4.18 (git: 4eed221) Ever since last week, a very strange problem happened 3 times. The FreeSWITCH servers randomly loose connectivity with our main router (gateway). FS servers can be reached and pinged from the rest of servers, they also can ping and reach all other servers but when we ping router from inside FS servers they cannot ping and reach the router. The only way we can get them working again is by: ifconfig eth1 down sleep 3 ifconfig eth1 up route add default gw 208.65.xxx.xxx eth1 The rest of our 20 servers are all running Ubuntu 14.04 and most of them are under heavy load, this only happens with FS servers. Does any one have any clue about this bizarre situation? Any one know under what circumstances a server might loose connectivity and routing to its gateway? Any pointer for debugging or suggestion is highly appreciated. Thank you, Moe