HA Split-Brain: I'm looking for details on how ADC...
# citrix-netscalera
Arthur
08/21/2024, 6:23 AMHA Split-Brain: I'm looking for details on how ADC behaves during long term connection loss between them.
There seems to be very little documentation based on this topic. My questions are:
• What's the time at which ADC switches to split-brain (default)
• What happens? (Based on documentation it seems to be loss of ADC functionality)
• What will happen when communication between ADC will start again?
j
jvitech
08/21/2024, 9:59 AMBased on real xp
1. After the HA packets is loss X times.
2. Each node will become active so you have 2 active NS, twice the VIPs, SNIPs, etc
3. One of the node will become passive.
a
Arthur
08/21/2024, 12:15 PM1. What’s default X times ?
2. What’s the impact? In my opinion nothing will work anymore because of IP’s duplication
3. I’m not sure about it… how with situation from point 2 ?
r
Richard Faulkner
08/21/2024, 1:19 PMBy default, NetScaler (NS) sends heartbeats every 200ms and dead interval is 3sec. After three seconds, a peer node is marked DOWN if heartbeat messages are not received from the peer node. During sync, this is extended as the VLAN settings being sync'ed can cause heartbeats to be missed for more than 3 seconds.
Richard Faulkner
08/21/2024, 1:21 PMDuplicating IPs will cause everything to be down, provided both can properly speak to the network. This is not guaranteed since there is some reason why the heartbeats failed. Truthfully, the impact will depend on the cause of the heartbeats being missed.
Richard Faulkner
08/21/2024, 1:22 PMand 3, this is because they will come to an agreement as to who is Primary.
👍 1
j
jvitech
08/22/2024, 8:52 AM2. If you are in a split brain scenario, duplicate IPs won't matter and that's what you want.
3. Once the split brain has been resolved, connectivity between the NS then HA will recover.
In our case, we have 2 datacenter and in a split brain that's how it works ( I have my HA heartbeat on ALL NetScaler interfaces working).
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