Description:
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I read via PHP function snmp2_real_walk OID value '.1.3.6.1.2.1.17.4.3.1.1' for get MAC address from Cisco switch device. Problem is, that some results (randomly around the 50 results of the 200) return bad characters (yet I have found a mistake if I read only MAC addresses). Ie.:

correct output examples:
 [Dot1dTpFdbAddres] => 30 05 5C 38 A7 8C
 [Dot1dTpFdbAddres] => C0 7B BC 0E 56 18

wrong output examples - device return randomly none-hex value for hex values, ie.:
[iso.3.6.1.2.1.17.4.3.1.1.92.38.10.129.123.27] => Hex-STRING: 5C 26 0A 81 7B 1B 
[iso.3.6.1.2.1.17.4.3.1.1.120.69.196.42.25.241] => Hex-STRING: 78 45 C4 2A 19 F1 
[iso.3.6.1.2.1.17.4.3.1.1.120.69.196.42.27.169] => Hex-STRING: 78 45 C4 2A 1B A9 
[iso.3.6.1.2.1.17.4.3.1.1.120.69.196.42.34.45] => STRING: "xE�*\"-"
[iso.3.6.1.2.1.17.4.3.1.1.120.172.192.142.199.214] => STRING: "x�����"
[iso.3.6.1.2.1.17.4.3.1.1.124.30.179.254.9.201] => Hex-STRING: 7C 1E B3 FE 09 C9 

If I try read OID '.1.3.6.1.2.1.17.4.3.1.1' from program Getif, I have got correct results.

The tested solution that fails:
 PHP - Chnaged snmp2_real_walk by snmprealwalk
 Changed encoding of files (UTF8, ANSI)
 SNMP longer timeout and try add PHP sleep() function
 PHP directive: snmp_set_oid_numeric_print(1)
 PHP directive: snmp_set_quick_print(true)
 PHP directive: snmp_set_enum_print(true)
 PHP directive: snmp_set_valueretrieval(SNMP_VALUE_LIBRARY and SNMP_VALUE_PLAIN)

Resolution - add new parameter for:
 snmprealwalk
 snmp2_real_walk
for forced return Hex-STRING result.

Test script:
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$arrDot1dTpFdbAddress = snmprealwalk("SomeIp:161", "ReadCommunity", ".1.3.6.1.2.1.3.1.1.2", (1000000 * 1), 3);
        
    echo '<pre>';
    print_r($arrDot1dTpFdbAddress);
    echo '</pre>';