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Forum Discussion

Gonzalo_Arce_17's avatar
Gonzalo_Arce_17
Icon for Nimbostratus rankNimbostratus
Mar 31, 2016

vlan failsafe don`t work on vcmp guest

Hello,   I have a 2x5250V (VCMP). I have installed three guests (Prod,dmz and QA) on both of them host. These Guests are connected on the same Vlans for HA & the following vlan for each guest:   ...
application delivery
LTM
vcmp
vlan failsafe
IanB's avatar
IanB
Icon for Employee rankEmployee
Mar 31, 2016

I'm not sure I fully understand your question, but I think you're staying that you have three pairs of vcmp guests, and two of them are working with vlan failsafe, but the third is not ? Is that correct ?

 

If so, I suggest you run tcpdump -i on both guests, to see what traffic is still being seen there, compared with the traffic seen on the other two vlans. Is the VLAN really totally inactive ?

 

VLAN failsafe is a timer that resets every time it receives a packet. If it reaches half of the timeout value, it starts sending ARP requests out to try and elicit a response. At 3/4s of the timeout, it starts pinging 224.0.0.1 to try and get a response. If none of that works, it will trigger failover.

 

Note that the vlan failsafe configuration is not part of the shared configuration, so make sure you have configured the same values on both guests.

 

Overview of VLAN failsafe

 

Note that VLAN failsafe can be problematic if both devices share the same VLAN, as the gratuitous packets from one device end up keeping the other one alive. In such a situation, Gateway failsafe is more appropriate, but that can have problems too, where the loss of the common gateway router causes both devices to go standby, since both see it as being down.