diff --git a/doc/snmp_agent.txt b/doc/snmp_agent.txt
index 8b08f11e..574508d6 100644
--- a/doc/snmp_agent.txt
+++ b/doc/snmp_agent.txt
@@ -98,6 +98,15 @@ Exactly every 10 msec the SNMP uptime timestamp must be updated with
 snmp_inc_sysuptime(). You should call this from a timer interrupt
 or a timer signal handler depending on your runtime environment.
 
+A alternative way it to update the SNMP uptime timestamp is to do a call like
+snmp_add_sysuptime(100) each 1000ms (which is bigger "step", but call to
+a lower frequency). Another one is to not call snmp_inc_sysuptime() or
+snmp_add_sysuptime(), and to define the SNMP_GET_SYSUPTIME(sysuptime) macro.
+This one is undefined by default in mib2.c. SNMP_GET_SYSUPTIME is called inside
+snmp_get_sysuptime(u32_t *value), and enable to change "sysuptime" value only
+when it's queried (any direct call to "sysuptime" is changed by a call to 
+snmp_get_sysuptime).
+
 
 3 Private MIBs
 ==============