For example:
Site 0001
Data:10.0.0.0/24
Voice: 10.0.1.0/24
summary route : 10.0.0.0/23
Site 0002
Data:10.0.2.0/24
Voice: 10.0.3.0/24
summary route: 10.0.2.0/23
....cont...
site 0129
Data:10.1.0.0/24
Voice: 10.1.1.0/24
summary route: 10.1.0.0/23
site 0130
Data:10.1.2.0/24
Voice: 10.1.3.0/24
summary route: 10.1.2.0/23
so 3rd octet is odd number assigned to voice, and even number assigned to data; for security team to recongize voice prefix, use an ACL with wildcast to filter odd number on third octet, started from 10.0.1.0 0.0.254.255, 10.1.1.0 0.0.254.255......, 10.1.1.0 0.0.254.255 etc; for 10.0.1.0 0.0.254.255, any IP in binary that started with 00001010.00000000.xxxxxxx1.xxxxxxxx will be matched (x = either 0 or 1), covert 3rd octet into dec, for example, 10000001 = 129 which is a voice VLAN.

The two practical OSPF convergence improvements are enabling Bidirectional Forwarding Detection and tuning OSPF timers and throttling behavior. Cisco describes BFD as a protocol designed to provide fast forwarding-path failure detection across media, encapsulations, topologies, and routing protocols. With OSPF, BFD allows a neighbor failure to be detected rapidly without depending only on the OSPF dead interval.
OSPF parameters can also be tuned, including SPF scheduling, LSA generation, and LSA arrival throttling, so the control plane reacts quickly but not recklessly during instability. Merging all areas into one backbone area is not a convergence improvement; it usually increases the size of the link-state database and the impact of topology changes. Making every nonbackbone area stub may reduce external LSA scope, but it is not universally valid and does not directly solve failure detection. Spanning the same IP network across multiple OSPF areas is a poor design and can create operational ambiguity. Therefore, BFD plus careful OSPF parameter tuning are the appropriate convergence-focused design actions.

Explanation:
Graphical user interface, application Description automatically generated