Symptom
Issue was found in 4.3.4 and reproduced in the lab for 5.2.4. Router medved has repro, but it is easy to reproduce on any testbed.
1. Configure interface to follow te0000-11-han
RP/0/RSP1/CPU0:medved(config-subif)#router hsrp
RP/0/RSP1/CPU0:medved(config-hsrp)#interface TenGigE1/0/0/4.2023
RP/0/RSP1/CPU0:medved(config-hsrp-if)# address-family ipv4
RP/0/RSP1/CPU0:medved(config-hsrp-ipv4)# hsrp 1403 slave
RP/0/RSP1/CPU0:medved(config-hsrp-slave)# follow te0000-11-han
RP/0/RSP1/CPU0:medved(config-hsrp-slave)# address 10.88.40.100
RP/0/RSP1/CPU0:medved(config-hsrp-slave)#commit
Tue Mar 8 14:13:02.869 CET
2.Reconfigure interface to follow te0000-11-hby
RP/0/RSP1/CPU0:medved(config)#router hsrp
RP/0/RSP1/CPU0:medved(config-hsrp)# interface TenGigE1/0/0/4.2023
RP/0/RSP1/CPU0:medved(config-hsrp-if)# address-family ipv4
RP/0/RSP1/CPU0:medved(config-hsrp-ipv4)# hsrp 1403 slave
RP/0/RSP1/CPU0:medved(config-hsrp-slave)# follow te0000-11-hby
RP/0/RSP1/CPU0:medved(config-hsrp-slave)#commit
Tue Mar 8 14:15:00.103 CET
RP/0/RSP1/CPU0:medved(config-hsrp-slave)#
3. Running config show recent changes correctly.
RP/0/RSP1/CPU0:medved#sh run router hsrp interface TenGigE1/0/0/4.2023
Tue Mar 8 14:34:44.558 CET
router hsrp
interface TenGigE1/0/0/4.2023
address-family ipv4
hsrp 1403 slave
follow te0000-11-hby
address 10.88.40.100
4. HSRP show incorrect follow group.
RP/0/RSP1/CPU0:medved#sh hsrp TenGigE1/0/0/4.2023 detail
Tue Mar 8 14:35:48.304 CET
TenGigE1/0/0/4.2023 - IPv4 Group 1403 (version 2)
Slave to te0000-11-han
Local state is Active
Hot standby IP address is 10.88.40.100 configured
Standby virtual mac address is 0000.0c9f.f57b, state is active
Conditions
Old group which was followed has the same length of the new group to be followed. Further name of old followed group and name of new followed group do not differ at first character (Eg issue does not happen old group is hsrp-1 and new group is Hsrp-2)
Workaround
workaround is to reconfigure the group
