Hi @Muthukumar1 !
If your router is running Comware 7, then it should have this command - https://support.hpe.com/hpesc/public/docDisplay?docId=c03890429&docLocale=en_US , Page 29. But you must have a line card (LPU Module) that either has Layer 2 (bridged) interfaces or interfaces that can be converted to bridged with command "port link-mode bridge".
Also, keep in mind that you can connect BAGG on 5900 to a RAGG with sub-interfaces on HSR6800, because technically these two configs are equal:
Configuration #1:
interface Bridge-Aggregation1
link-aggregation mode dynamic
port link-type trunk
port trunk permit vlan 10 20
#
inteface Vlan-interface10
ip address 10.0.10.1 24
#
inteface Vlan-interface20
ip address 10.0.20.1 24
Configuration #2:
interface Route-aggregation1
link-aggregation mode dynamic
#
interface Route-aggregation1.10
vlan-type dot1q vid 10
ip address 10.0.10.1 24
#
interface Route-aggregation1.20
vlan-type dot1q vid 20
ip address 10.0.20.1 24
However, if you don't feel comfortable with BAGG-to-RAGG config, keep it simple and use BAGG on both sides if available. Aslo you must use BAGG-to-BAGG when on the HSR6800 you have other ports except aggregation in Vlans that traverses the aggregation like VLAN 10 and 20 in my scenario. So BAGG-to-RAGG is ok when you need to terminate VLAN on the HSR.
I didn't say MSR36-20 has this command, I confirmed HSR6802 should have it. Also, this MSR is not known to me, this is H3C's product number, HPE uses different numbers, I guess we have analogue from MSR3000 series, but I couldn't find any information about it. I doubt it was bought from HPE, to be honest. So, unfortunately, I can't say nothing about this MSR36-20, but the command reference guide for HSR6800 clearly states that "interface Bridge-Aggregation" should be there. Just FYI - Comware 7 is not a single image for all devices. Instead, every device family or even a device has its own version of Comware 7 even sometimes with slightly different feature sets. Therefore we can't judge HSR by looking at MSR.