advbase: This optional parameter specifies how often, in seconds, to advertise that we're a member of the redundancy group. The default is 1 second. Acceptable values are from 1 to 255.
advskew: This optional parameter specifies how much to skew the advbase when sending CARP advertisements. By manipulating advskew, the master CARP host can be chosen. The higher the number, the less preferred the host will be when choosing a master. The default is 0. Acceptable values are from 0 to 254. If advbase is long you can risk slow switchover in a failure situation. It needs to be a sensible time based on system load. And network delay. However network delay is normally not something you have to take into account. Skew will help you force one to become master by default. And if you have more then 2 hosts you can controll primary secondary thirtiary etc. Lets say you have a very fast primary. A slower older secondary. And a even slower older third. This way you can set primary to 1 secondary to 128 and third to 254 and they will be elected master based on this. I assume that is why you need both. Advbase should be the same on all hosts in a carp group. Skew is something you would want to be different if you want to controll which one will be active. -lsf 11. sep. 2014 12:27 skrev "Martin T" <[email protected]> følgende: > Jim, > > thanks for the reply! So do you agree that it's not just the "advskew" > value, but the system with lowest "advbase"+"advskew" value will take > the master role? And it seems that "advbase" is byte number 40 and > "advskew" is byte number 37 in CARP advertisements. For example in > this CARP advertisement "advbase" is 2(02) and "advskew" is 254(fe): > > 0x0020: 0012 2122 fe07 0002 f66a 97c4 8a3a 47f9 ..!".....j...:G. > > > Last but not least, I still don't quite understand why both "advbase" > and "advskew" are available.. One could determine the master/backup > role solely with "advbase", couldn't he? > > > thanks, > Martin > > On 9/10/14, Jim Pingle <[email protected]> wrote: > > On 9/10/2014 5:15 AM, Martin T wrote: > >> 1) Why does the messages interval matter to CARP? Is CARP designed in > >> a way that CARP preferres system which announces CARP messages with > >> shortest interval? > > > > Yes, the fastest advertisement wins the election and becomes master. > > > >> 2) Why is "advskew" needed if one could determine the master/backup > >> role solely with "advbase"? > > > > See above. advbase is a base time added to the skew. (+1 sec per base > > value) > > > > On slower networks you need to use a higher advbase on both to account > > for lag in local network equipment such as when the two nodes are in > > different buildings or similar situations. > > > > Typically, base matches on both and you set the skew to give your > > preferred primary node preference. > > > > Jim > > _______________________________________________ > > List mailing list > > [email protected] > > https://lists.pfsense.org/mailman/listinfo/list > > > _______________________________________________ > List mailing list > [email protected] > https://lists.pfsense.org/mailman/listinfo/list >
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