> Base interface configuration

#  ifconfig -a
eri0: flags=1004843<UP,BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 1500 index 2
        inet 165.137.7.160 netmask ffffff00 broadcast 165.137.7.255
        ether 0:3:ba:5:1c:bc 
eri1: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 3
        inet 192.168.17.17 netmask ffffff00 broadcast 192.168.17.255
        ether 0:3:ba:5:1c:bc 
eri0: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 2
        inet6 fe80::203:baff:fe05:1cbc/10 
        ether 0:3:ba:5:1c:bc 
eri1: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 3
        inet6 fe80::203:baff:fe05:1cbc/10 
        ether 0:3:ba:5:1c:bc 

> Interface status from SNMP 

snmpbulkwalk -v 2c -c t3stTHIS udp6:[::1] ifAdminStatus
getaddrinfo:  node name or service name not known
IF-MIB::ifAdminStatus.1 = INTEGER: up(1)
IF-MIB::ifAdminStatus.2 = INTEGER: up(1)
IF-MIB::ifAdminStatus.3 = INTEGER: up(1)

> Turn off the IPv4 stack on eri1

# ifconfig eri1 unplumb

> New interface configuration

# ifconfig -a
eri0: flags=1004843<UP,BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 1500 index 2
        inet 165.137.7.160 netmask ffffff00 broadcast 165.137.7.255
        ether 0:3:ba:5:1c:bc 
eri0: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 2
        inet6 fe80::203:baff:fe05:1cbc/10 
        ether 0:3:ba:5:1c:bc 
eri1: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 3
        inet6 fe80::203:baff:fe05:1cbc/10 
        ether 0:3:ba:5:1c:bc 

> Still showing 3 interfaces up;

snmpbulkwalk -v 2c -c t3stTHIS udp6:[::1] ifAdminStatus
getaddrinfo:  node name or service name not known
IF-MIB::ifAdminStatus.1 = INTEGER: up(1)
IF-MIB::ifAdminStatus.2 = INTEGER: up(1)
IF-MIB::ifAdminStatus.3 = INTEGER: up(1)

> Turn off the IPv6 stack on eri1

# ifconfig eri1 inet6 unplumb

> New interface configuration

# ifconfig -a
eri0: flags=1004843<UP,BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 1500 index 2
        inet 165.137.7.160 netmask ffffff00 broadcast 165.137.7.255
        ether 0:3:ba:5:1c:bc 
eri0: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 2
        inet6 fe80::203:baff:fe05:1cbc/10 
        ether 0:3:ba:5:1c:bc 

> SNMP is now showing interface 2 (eri1) down
snmpbulkwalk -v 2c -c t3stTHIS udp6:[::1] ifAdminStatus
getaddrinfo:  node name or service name not known
IF-MIB::ifAdminStatus.1 = INTEGER: up(1)
IF-MIB::ifAdminStatus.2 = INTEGER: up(1)
IF-MIB::ifAdminStatus.3 = INTEGER: down(2)

>So far, so good. Here is where it gets weird. Turn IPv4 stack on eri1 back on:

# ifconfig eri1 plumb
# ifconfig eri1 dhcp
# ifconfig eri1 up

# ifconfig -a             
eri0: flags=1004843<UP,BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 1500 index 2
        inet 165.137.7.160 netmask ffffff00 broadcast 165.137.7.255
        ether 0:3:ba:5:1c:bc 
eri1: flags=1004843<UP,BROADCAST,RUNNING,MULTICAST,DHCP,IPv4> mtu 1500 index 4
        inet 165.137.8.79 netmask ffffff00 broadcast 165.137.8.255
        ether 0:3:ba:5:1c:bc 
eri0: flags=2000841<UP,RUNNING,MULTICAST,IPv6> mtu 1500 index 2
        inet6 fe80::203:baff:fe05:1cbc/10 
        ether 0:3:ba:5:1c:bc 

> SNMP is now showing 4 interfaces???

snmpbulkwalk -v 2c -c t3stTHIS udp6:[::1] ifAdminStatus
getaddrinfo:  node name or service name not known
IF-MIB::ifAdminStatus.1 = INTEGER: up(1)
IF-MIB::ifAdminStatus.2 = INTEGER: up(1)
IF-MIB::ifAdminStatus.3 = INTEGER: down(2)
IF-MIB::ifAdminStatus.4 = INTEGER: up(1)