Espen, I see, thanks! However, while not the best practice, one could determine the master/backup role solely with "advbase", couldn't he? Thats because host with the lowest "advbase"+"advskew" value(not just the "advskew" value) should be the preferred one?
thanks, Martin On Thu, Sep 11, 2014 at 7:34 PM, Espen Johansen <pfse...@gmail.com> wrote: > 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" <m4rtn...@gmail.com> 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 <li...@pingle.org> 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 >> > List@lists.pfsense.org >> > https://lists.pfsense.org/mailman/listinfo/list >> > >> _______________________________________________ >> List mailing list >> List@lists.pfsense.org >> https://lists.pfsense.org/mailman/listinfo/list > > > _______________________________________________ > List mailing list > List@lists.pfsense.org > https://lists.pfsense.org/mailman/listinfo/list _______________________________________________ List mailing list List@lists.pfsense.org https://lists.pfsense.org/mailman/listinfo/list
