1. I installed net-snmp 5.7.3 on Ubuntu 1704 (but the following problem was observed on many versions of Ubuntu like 1604, 1404)

As i think, this switch is necessary for the purpose of accessing routing MIBs which must be responsed by zebra.

make[2]: Entering directory '/home/theuser/frr/FRR3'
  CLIPPY   ospfd/ospf_vty_clippy.c
  CLIPPY   lib/plist_clippy.c
  CC       lib/lib_libfrrsnmp_la-agentx.lo
  CC       lib/lib_libfrrsnmp_la-smux.lo
  CC       lib/lib_libfrrsnmp_la-snmp.lo
  CCLD     lib/libfrrsnmp.la
/usr/bin/ld: /usr/local/lib/libnetsnmp.a(scapi.o): relocation R_X86_64_PC32 against symbol `usmHMACMD5AuthProtocol' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status
Makefile:2379: recipe for target 'lib/libfrrsnmp.la' failed
make[2]: *** [lib/libfrrsnmp.la] Error 1
make[2]: Leaving directory '/home/theuser/frr/FRR3'
Makefile:3194: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/theuser/frr/FRR3'
Makefile:1867: recipe for target 'all' failed

If net-snmp was not installed, there was no error when making FRR, BUT a similar error was raised when trying to make net-snmp after frr !!!

If i disable --enable-snmp=agentx there is no error! But the system will not respond to snmp requests that ask for routing information.