The Asus specific MIBS have been removed from Merlin as they are considered a security hole.
Disregarding that, I want to monitor the router. So, I got the mibs from the 378.49_4 tag.
First, we enable SNMP via the web GUI. It is under Administration. The community string you set will be used in the snmp* commands so in that sense, you can use it like a password. There is no real way to secure v2c and I have not figured out how to make this a v3-only installation. Forum posts like the one above indicate that it is not trivial.
After repeated invokations of
$ snmpwalk -Os -c <get community string> -v2c 192.168.1.1 2>/tmp/q
$ cat /tmp/q
to figure out the missing modules, I got all the MIBS from net-snmp, dumped them in /usr/share/snmp/mibs and created an /etc/snmp/snmp.conf file like so,
mibdirs /usr/share/snmp/mibs
mibs +ALL
You can figure out the MIBS you need one by one, but this was faster. Now, snmpwalk should should have descriptive names instead of numeric OIDs.
$ snmpwalk -Os -c <community string> -v2c 192.168.1.1
sysDescr.0 = STRING: Linux euler 2.6.36.4brcmarm #1 SMP PREEMPT Sat May 12 22:04:57 EDT 2018 armv7l
sysObjectID.0 = OID: linux
sysUpTimeInstance = Timeticks: (13740954) 1 day, 14:10:09.54
sysContact.0 = STRING: alephnull@local
sysName.0 = STRING: euler
sysLocation.0 = STRING: tv-room
sysORLastChange.0 = Timeticks: (9) 0:00:00.09
sysORID.1 = OID: ip
sysORID.2 = OID: snmpMIB
sysORID.3 = OID: tcpMIB
...