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To start with, I'm unsure what your non-LLQ bandwidth allocations are as you didn't define bandwidth for class-default nor did you specify which IOS version you're using. (NB: there's some differences between pre-HQF and HQF CBWFQ.)
1. The voice-class 20% is calculated off the parent policy – hence voice-class gets a max 20% of 400M = 80M strict priority. Policed at 80M during congestions.
Correct.
2. When there is no congestion on the link– that is say Voice-class, class3, class1, default-class have NO packets in it; can Class2 scavenge upto 400Mbps ?? OR can Class2 go upto 320Mbps only (even though there is nothing in voice class)
No, not congestion on the link, congestion due to the shaper.
With your posted configuration, any of the non-LLQ classes can use the full bandwidth allowed by the shaper, 400 Mbps. (And as you described in your 1st question, so can LLQ if there's no congestion. I.e. its implicit policer only triggers when there's packets queued to the LLQ.)
2. During periods of high congestion, when all classes are congested to the full. Can you confirm when using “bandwidth remaining percent ” command, as per the config- if –
a.Class3 will get a guaranteed minimum 128Mbps (40% of 320Mbps)
b.Class2 will get a guaranteed minimum of 57.6 Mbps (30% of remaining [400-80-128]) OR
c.Class2 will get a guaranteed minimum of 96 Mbps (30%of 320Mbps)
d.Class1 will get a guaranteed minimum of 13.44Mbps (10% of remaining [400-80-128-57.6]) OR
e.Class1 will get a guaranteed minimum of 32Mbps (10% of 320Mbps)
Unsure because what class-default's percentage is undefined in your posting.
Bandwidth percentages are a bit misleading, because they are only "correct" when you allocate all 100%. Otherwise they effectively set ratios between classes. For example, ignoring class-default (i.e. zero traffic) and assuming all your non-class-default classes were congested, your LLQ gets 20%. Your other class ratios are 4:3:1 or 4/8%, 3/8% and 1/8% of the remaining 80%, or .8*4/8%, .8*3/8% and .8*1/8% of your 400 Mbps.
3. Where does the priority percent calculates against interface bandwidth In this case ?? should the calculations not be based on the parent policy map in this case ?
As your priority class is in the child policy, its priority % is against the bandwidth it believes it has, in this case the 400 Mbps. If you also defined a priority class in the parent policy, by default, it would takes its percentage from 1 Gbps. (Some or all IOS versions, I recall, [for the interface policy classes, not child policy classes] will base their percentage against the interface's bandwidth statement.)
