How to safely switch from Multicast Heartbeats to Unicast Heartbeats?

[sameh]

I have a cluster of 4 SteelApp Traffic Managers that has always been using multicast communication for heartbeats between TMs.

I want to do big network changes that will make multicast temporarily unavailable. Because of this, I plan to fully switch the cluster to unicast communication. At least for the time of the network migration.

How does a cluster behave if you switch it to unicast? In case of failure I am mainly worried about a TM unable to communicate with the others, trying to grab all traffic group IP addresses.

Is there a way to do this change safely? Maybe disabling temporarily fault tolerance?

[aclarke · Accepted solution]

Sameh,

    There shouldn't be any problems.  A TCPDUMP on my system during a multicast to unicast conversion, it just keeps ticking.  So long as the STM's can see each other and can communicate via UDP 9090, you should be good.

[email protected]:~# tcpdump -ni any  udp port 9090
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
<...>

00:17:47.173873 IP 1.1.33.205.39086 > 239.100.1.1.9090: UDP, length 70
00:17:47.461110 IP 1.1.33.12.59784 > 239.100.1.1.9090: UDP, length 70
00:17:47.469244 IP 1.1.33.11.35666 > 239.100.1.1.9090: UDP, length 70
00:17:47.969215 IP 1.1.33.11.60123 > 1.1.33.12.9090: UDP, length 70
00:17:48.460930 IP 1.1.33.12.39856 > 1.1.33.11.9090: UDP, length 70
00:17:48.470873 IP 1.1.33.11.60123 > 1.1.33.12.9090: UDP, length 70

Per the documentation though, make sure you have a non zero value for the "state_sync_time" setting: