Update-2:

Replaced PORT6-N2 with PORT5-N2 as below.

root@cic-1:~# neutron router-update R1 --routes type=dict list=true destination=15.0.0.0/24,nexthop=11.1.2.3 destination=2111:12f:862:18::/64,nexthop=2001:db8:abcd:11:f816:3eff:feb8:ef29 destination=15.0.0.0/24,nexthop=12.23.34.3 destination=2111:12f:862:18::/64,nexthop=2025:caf:3214:12:f816:3eff:fef0:9738
Updated router: R1

root@cic-1:~# neutron port-list | grep PORT5
| be09ff9b-afb6-4b9b-bbbc-a663f6c9670b | PORT5-N2 | fa:16:3e:f0:97:38 | {"subnet_id": "e4094270-337e-48a7-bbad-7b81bddf9b54", "ip_address": "12.23.34.3"}         

Port6-N2 entries are removed but the first update entries for PORT2-N1 persists

root@compute-0-1:~# sudo ovs-ofctl dump-groups br-int -O Openflow13 | grep 150017
 group_id=150017,type=select,bucket=actions=group:150001,bucket=actions=group:150009
root@compute-0-1:~# sudo ovs-ofctl dump-groups br-int -O Openflow13 | grep 150018
 group_id=150018,type=select,bucket=actions=group:150002,bucket=actions=group:150010,bucket=actions=set_field:0x444->tun_id,set_field:fa:16:3e:9a:bb:f4->eth_dst,load:0x200->NXM_NX_REG6[],resubmit(,220)
root@compute-0-1:~# sudo ovs-ofctl dump-groups br-int -O Openflow13 | grep 150002
 group_id=150002,type=all,bucket=actions=set_field:fa:16:3e:fd:61:02->eth_src,set_field:fa:16:3e:b8:ef:29->eth_dst,load:0xd00->NXM_NX_REG6[],resubmit(,220)
 group_id=150018,type=select,bucket=actions=group:150002,bucket=actions=group:150010,bucket=actions=set_field:0x444->tun_id,set_field:fa:16:3e:9a:bb:f4->eth_dst,load:0x200->NXM_NX_REG6[],resubmit(,220)
root@compute-0-1:~# sudo ovs-ofctl dump-groups br-int -O Openflow13 | grep 150010
 group_id=150010,type=all,bucket=actions=set_field:fa:16:3e:93:27:fd->eth_src,set_field:fa:16:3e:f0:97:38->eth_dst,load:0x1100->NXM_NX_REG6[],resubmit(,220)
 
root@compute-0-2:~# sudo ovs-ofctl dump-groups br-int -O Openflow13 | grep 150018
 group_id=150018,type=select,bucket=actions=group:150006,bucket=actions=set_field:0x444->tun_id,set_field:fa:16:3e:b8:ef:29->eth_dst,load:0x500->NXM_NX_REG6[],resubmit(,220),bucket=actions=set_field:0x430->tun_id,set_field:fa:16:3e:f0:97:38->eth_dst,load:0x500->NXM_NX_REG6[],resubmit(,220)
root@compute-0-2:~# sudo ovs-ofctl dump-groups br-int -O Openflow13 | grep 150006
 group_id=150006,type=all,bucket=actions=set_field:fa:16:3e:fd:61:02->eth_src,set_field:fa:16:3e:9a:bb:f4->eth_dst,load:0xf00->NXM_NX_REG6[],resubmit(,220)