O snmpd não exporta nenhuma métrica para subinterfaces. Tenho certeza que o Linux nem registra essas métricas. Observe:
$ ifconfig -a
<cut non-eth1 data>
eth1 Link encap:Ethernet HWaddr E4:11:5B:E0:14:5C
inet addr:87.233.215.178 Bcast:87.233.215.191 Mask:255.255.255.240
inet6 addr: fe80::e611:5bff:fee0:145c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:909395198 errors:5 dropped:0 overruns:0 frame:0
TX packets:939665657 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:738107052290 (687.4 GiB) TX bytes:799183242768 (744.2 GiB)
eth1:179 Link encap:Ethernet HWaddr E4:11:5B:E0:14:5C
inet addr:87.233.215.179 Bcast:87.233.215.191 Mask:255.255.255.240
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth1:180 Link encap:Ethernet HWaddr E4:11:5B:E0:14:5C
inet addr:87.233.215.180 Bcast:87.233.215.191 Mask:255.255.255.240
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth1:181 Link encap:Ethernet HWaddr E4:11:5B:E0:14:5C
inet addr:87.233.215.181 Bcast:87.233.215.191 Mask:255.255.255.240
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth1:182 Link encap:Ethernet HWaddr E4:11:5B:E0:14:5C
inet addr:87.233.215.182 Bcast:87.233.215.191 Mask:255.255.255.240
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
$ snmpwalk -v3 -x AES -X ........ -u ........ -a SHA -A ........ -l authPriv gateway-machine IF-MIB::ifDescr
IF-MIB::ifDescr.1 = STRING: lo
IF-MIB::ifDescr.2 = STRING: eth0
IF-MIB::ifDescr.3 = STRING: eth1
Nenhum contador de pacotes na saída ifconfig para os dispositivos: 179-: 182, nenhuma interface listada na saída snmpwalk.