SNMP Interface name after update to FortiOS 5.4

What do  you mean by snmp interface names? Any examples ?

You can query  the interface well known  ifTable  &  any part of the IF-MIB and the related  Index descriptions aliases if that what your talking about.

You can get an ideal of what the fortiOS  is doing via the following dig commands

  diag debug reset 

  diag debug en 

  diag debug  app snmpd -1

Than have your poller poll the  device index and monitor the device  snap output the debug output 

snmpwalk   -c  <community> -v2c  x.x.x.x  interface

e.g

snmpd: <msg> 47 bytes 70.195.211.101:58396 -> 192.0.1.1/192.0.2.1:161 (itf 46.46)

snmpd: checking if community "nogocmmro" is valid

snmpd: checking against community "1plus2eq2C0mun1"

snmpd: name mismatch.

snmpd: checking against community "test1234"

snmpd: request 1(root)/46/70.195.211.101 == comm 1/0/70.195.211.101/255.255.255.255

snmpd: matched community "nogocmmro"

snmpd: get-next: ifEntry.1.96 -> () -> 0

snmpd: eoq_ifEntry()

snmpd: </msg> 1