Python の SNMPライブラリ PySNMP でベンダの拡張MIBを取得できるようにするのに、やり方が分からず結構ハマったのでそのメモです。
結果的に、超簡単に利用できるということが分かりました。。。
利用したのはJuniper vSRXと、その拡張MIBです。他の拡張MIBでも同じだと思います。
OSはCentOS7を利用してます。

PySNMPインストール

pip で pysnmp, pysnmp-mibs をインストール。

[centos@ip-172-31-2-50 ~]$ sudo pip install pysnmp pysnmp-mibs

Juniper公式サイトからのMIBをダウンロード

(今回はvSRXの JUNOS15.1X49 のMIBをダウンロードして解凍する。)

[centos@ip-172-31-2-50 ~]$ wget http://www.juniper.net/documentation/software/junos/junos151X49/juniper-mibs-15.1X49-D140.2.zip
[centos@ip-172-31-2-50 ~]$ unzip juniper-mibs-15.1X49-D140.2.zip
[centos@ip-172-31-2-50 ~]$ ls juniper-mibs-15.1X49-D140.2/
JuniperMibs  StandardMibs

MIBテキストファイルからコンバート

mibdump.py を利用して、PySNMPから利用できるようにする。
JuniperMibs 配下のtxtファイルを全てコンバートする。
(コマンド一発でできる！！)

[centos@ip-172-31-2-50 ~]$ cd juniper-mibs-15.1X49-D140.2/
[centos@ip-172-31-2-50 juniper-mibs-15.1X49-D140.2]$ mibdump.py JuniperMibs/*
Source MIB repositories: /home/centos/juniper-mibs-15.1X49-D140.2/JuniperMibs, file:///usr/share/snmp/mibs, http://mibs.snmplabs.com/asn1/@mib@
Borrow missing/failed MIBs from: http://mibs.snmplabs.com/pysnmp/notexts/@mib@
Existing/compiled MIB locations: pysnmp.smi.mibs, pysnmp_mibs
Compiled MIBs destination directory: /home/centos/.pysnmp/mibs
MIBs excluded from code generation: INET-ADDRESS-MIB, PYSNMP-USM-MIB, RFC-1212, RFC-1215, RFC1065-SMI, RFC1155-SMI, RFC1158-MIB, RFC1213-MIB, SNMP-FRAMEWORK-MIB, SNMP-TARGET-MIB, SNMPv2-CONF, SNMPv2-SMI, SNMPv2-TC, SNMPv2-TM, TRANSPORT-ADDRESS-MIB
MIBs to compile: mib-jnx-alarm, mib-jnx-analyzer, mib-jnx-atm-cos, mib-jnx-atm, mib-jnx-bfd-exp, mib-jnx-bfd, mib-jnx-bgpmib2, mib-jnx-bl, mib-jnx-cfgmgmt, mib-jnx-chas-defines, mib-jnx-chassis-alarm, mib-jnx-chassis-fwdd, mib-jnx-chassis, mib-jnx-coll, mib-jnx-cos, mib-jnx-dcu, mib-jnx-dfc, mib-jnx-dom, mib-jnx-event, mib-jnx-ex-mac-notification, mib-jnx-exp, mib-jnx-ex-smi, mib-jnx-fabric-chassis, mib-jnx-firewall, mib-jnx-fru, mib-jnx-gen-set, mib-jnx-hostresources, mib-jnx-if-accounting, mib-jnx-if-extensions, mib-jnx-ifotn, mib-jnx-ipforward, mib-jnx-ipsec-flow-mon, mib-jnx-ipsec-monitor-asp, mib-jnx-ipv4, mib-jnx-ipv6, mib-jnx-jdhcp, mib-jnx-jdhcpv6, mib-jnx-js-auth, mib-jnx-js-cert, mib-jnx-js-dns, mib-jnx-js-flow, mib-jnx-js-idp, mib-jnx-js-if-ext, mib-jnx-js-ipsec-vpn, mib-jnx-js-nat, mib-jnx-js-packet-mirror, mib-jnx-js-policy, mib-jnx-jsrpd, mib-jnx-js-screening, mib-jnx-js-smi, mib-jnx-js-spu-monitoring, mib-jnx-js-utm-av, mib-jnx-jvae-infra, mib-jnx-jvae-node, mib-jnx-l2ald, mib-jnx-l2cp-features, mib-jnx-l2l3vpn-mcast, mib-jnx-l2tp, mib-jnx-ldp, mib-jnx-license, mib-jnx-lsys-securityprofile, mib-jnx-lsys-sp-authentry, mib-jnx-lsys-sp-cpu, mib-jnx-lsys-sp-flowgate, mib-jnx-lsys-sp-flowsess, mib-jnx-lsys-sp-natconebind, mib-jnx-lsys-sp-natdstpool, mib-jnx-lsys-sp-natdstrule, mib-jnx-lsys-sp-natpoipnum, mib-jnx-lsys-sp-natsrcnopatad, mib-jnx-lsys-sp-natsrcpatad, mib-jnx-lsys-sp-natsrcpool, mib-jnx-lsys-sp-natsrcrule, mib-jnx-lsys-sp-natstaticrule, mib-jnx-lsys-sp-policy, mib-jnx-lsys-sp-policywcnt, mib-jnx-lsys-sp-scheduler, mib-jnx-lsys-sp-zone, mib-jnx-mac, mib-jnx-mag, mib-jnx-mbg-smi, mib-jnx-mimstp, mib-jnx-mobile-gateway-aaa, mib-jnx-mobile-gateway-appfw, mib-jnx-mobile-gateway-charging, mib-jnx-mobile-gateway-dhcp, mib-jnx-mobile-gateway-example, mib-jnx-mobile-gateway-gtp, mib-jnx-mobile-gateway-rmps, mib-jnx-mobile-gateway-sgw-charging, mib-jnx-mobile-gateway-sgw-gtp, mib-jnx-mobile-gateway-sgw-mfwd, mib-jnx-mobile-gateway-sgw-sm, mib-jnx-mobile-gateway-sm-ip-pool, mib-jnx-mobile-gateways, mib-jnx-mpls-ldp, mib-jnx-mpls, mib-jnx-mvpn, mib-jnx-oam, mib-jnx-optics, mib-jnx-optif, mib-jnx-ospfv3mib, mib-jnx-otn, mib-jnx-p2mp, mib-jnx-pae-extension, mib-jnx-pfe, mib-jnx-ping, mib-jnx-pmon, mib-jnx-power-supply-unit, mib-jnx-pppoe, mib-jnx-ppp, mib-jnx-pwatm, mib-jnx-pwtdm, mib-jnx-rmon, mib-jnx-rpf, mib-jnx-rpm-twamp, mib-jnx-rpm, mib-jnx-rps, mib-jnx-rsvp, mib-jnx-rtm, mib-jnx-scu, mib-jnx-secure-access-port, mib-jnx-services, mib-jnx-sipcommon, mib-jnx-smi, mib-jnx-soam-pm, mib-jnx-sonetaps, mib-jnx-sonet, mib-jnx-sp-nat, mib-jnx-sp, mib-jnx-subscriber, mib-jnx-syslog, mib-jnx-timing-notifications, mib-jnx-traceroute, mib-jnx-user-aaa, mib-jnx-util, mib-jnx-virtualchassis, mib-jnx-vlan, mib-jnx-vmon, mib-jnx-vpls-bgp, mib-jnx-vpls-generic, mib-jnx-vpls-ldp, mib-jnx-vpn
Destination format: pysnmp
Parser grammar cache directory: not used
Also compile all relevant MIBs: yes
Rebuild MIBs regardless of age: no
Dry run mode: no
Create/update MIBs: yes
Byte-compile Python modules: yes (optimization level no)
Ignore compilation errors: no
Generate OID->MIB index: no
Generate texts in MIBs: no
Keep original texts layout: no
Try various file names while searching for MIB module: yes
Created/updated MIBs: BFD-STD-MIB (mib-jnx-bfd-exp), BGP4-V2-MIB-JUNIPER (mib-jnx-bgpmib2), IEEE8021-CFM-MIB, IEEE8021-PAE-MIB, IEEE8021-TC-MIB, JNX-IPSEC-MONITOR-MIB (mib-jnx-ipsec-monitor-asp), JNX-L2TP-MIB (mib-jnx-l2tp), JNX-MPLS-TE-P2MP-STD-MIB (mib-jnx-p2mp), JNX-OPT-IF-EXT-MIB (mib-jnx-bl), JNX-OPT-IF-MIB (mib-jnx-optif), JNX-PPP-MIB (mib-jnx-ppp), JNX-PPPOE-MIB (mib-jnx-pppoe), JUNIPER-ALARM-EXT-MIB (mib-jnx-alarm), JUNIPER-ALARM-MIB (mib-jnx-chassis-alarm), JUNIPER-ANALYZER-MIB (mib-jnx-analyzer), JUNIPER-ATM-COS-MIB (mib-jnx-atm-cos), JUNIPER-ATM-MIB (mib-jnx-atm), JUNIPER-BFD-MIB (mib-jnx-bfd), JUNIPER-CFGMGMT-MIB (mib-jnx-cfgmgmt), JUNIPER-CHASSIS-CLUSTER-MIB (mib-jnx-jsrpd), JUNIPER-CHASSIS-DEFINES-MIB (mib-jnx-chas-defines), JUNIPER-CHASSIS-FWDD-MIB (mib-jnx-chassis-fwdd), JUNIPER-COLLECTOR-MIB (mib-jnx-coll), JUNIPER-DCU-MIB (mib-jnx-dcu), JUNIPER-DFC-MIB (mib-jnx-dfc), JUNIPER-DOM-MIB (mib-jnx-dom), JUNIPER-EVENT-MIB (mib-jnx-event), JUNIPER-EX-MAC-NOTIFICATION-MIB (mib-jnx-ex-mac-notification), JUNIPER-EX-SMI (mib-jnx-ex-smi), JUNIPER-EXPERIMENT-MIB (mib-jnx-exp), JUNIPER-FABRIC-CHASSIS (mib-jnx-fabric-chassis), JUNIPER-FIREWALL-MIB (mib-jnx-firewall), JUNIPER-FRU-MIB (mib-jnx-fru), JUNIPER-HOSTRESOURCES-MIB (mib-jnx-hostresources), JUNIPER-IFOPTICS-MIB (mib-jnx-optics), JUNIPER-IFOTN-MIB (mib-jnx-ifotn), JUNIPER-IPFORWARD-MIB (mib-jnx-ipforward), JUNIPER-IPSEC-FLOW-MON-MIB (mib-jnx-ipsec-flow-mon), JUNIPER-IPv4-MIB (mib-jnx-ipv4), JUNIPER-IPv6-MIB (mib-jnx-ipv6), JUNIPER-JDHCP-MIB (mib-jnx-jdhcp), JUNIPER-JDHCPV6-MIB (mib-jnx-jdhcpv6), JUNIPER-JS-AUTH-MIB (mib-jnx-js-auth), JUNIPER-JS-CERT-MIB (mib-jnx-js-cert), JUNIPER-JS-DNS-MIB (mib-jnx-js-dns), JUNIPER-JS-FLOW-MIB (mib-jnx-js-flow), JUNIPER-JS-IDP-MIB (mib-jnx-js-idp), JUNIPER-JS-IF-EXT-MIB (mib-jnx-js-if-ext), JUNIPER-JS-IPSEC-VPN-MIB (mib-jnx-js-ipsec-vpn), JUNIPER-JS-NAT-MIB (mib-jnx-js-nat), JUNIPER-JS-PACKET-MIRROR-MIB (mib-jnx-js-packet-mirror), JUNIPER-JS-POLICY-MIB (mib-jnx-js-policy), JUNIPER-JS-SCREENING-MIB (mib-jnx-js-screening), JUNIPER-JS-SMI (mib-jnx-js-smi), JUNIPER-JS-UTM-AV-MIB (mib-jnx-js-utm-av), JUNIPER-JVAE-INFRA-MIB (mib-jnx-jvae-infra), JUNIPER-JVAE-NODE-MIB (mib-jnx-jvae-node), JUNIPER-L2ALD-MIB (mib-jnx-l2ald), JUNIPER-L2CP-FEATURES-MIB (mib-jnx-l2cp-features), JUNIPER-LDP-MIB (mib-jnx-ldp), JUNIPER-LICENSE-MIB (mib-jnx-license), JUNIPER-LSYS-SECURITYPROFILE-MIB (mib-jnx-lsys-securityprofile), JUNIPER-LSYSSP-CPU-MIB (mib-jnx-lsys-sp-cpu), JUNIPER-LSYSSP-FLOWGATE-MIB (mib-jnx-lsys-sp-flowgate), JUNIPER-LSYSSP-FLOWSESS-MIB (mib-jnx-lsys-sp-flowsess), JUNIPER-LSYSSP-NATCONEBIND-MIB (mib-jnx-lsys-sp-natconebind), JUNIPER-LSYSSP-NATDSTPOOL-MIB (mib-jnx-lsys-sp-natdstpool), JUNIPER-LSYSSP-NATDSTRULE-MIB (mib-jnx-lsys-sp-natdstrule), JUNIPER-LSYSSP-NATPOIPNUM-MIB (mib-jnx-lsys-sp-natpoipnum), JUNIPER-LSYSSP-NATSRCNOPATAD-MIB (mib-jnx-lsys-sp-natsrcnopatad), JUNIPER-LSYSSP-NATSRCPATAD-MIB (mib-jnx-lsys-sp-natsrcpatad), JUNIPER-LSYSSP-NATSRCPOOL-MIB (mib-jnx-lsys-sp-natsrcpool), JUNIPER-LSYSSP-NATSRCRULE-MIB (mib-jnx-lsys-sp-natsrcrule), JUNIPER-LSYSSP-NATSTATICRULE-MIB (mib-jnx-lsys-sp-natstaticrule), JUNIPER-LSYSSP-POLICY-MIB (mib-jnx-lsys-sp-policy), JUNIPER-LSYSSP-POLICYWCNT-MIB (mib-jnx-lsys-sp-policywcnt), JUNIPER-LSYSSP-SCHEDULER-MIB (mib-jnx-lsys-sp-scheduler), JUNIPER-LSYSSP-ZONE-MIB (mib-jnx-lsys-sp-zone), JUNIPER-LSYSSPAUTHENTRY-MIB (mib-jnx-lsys-sp-authentry), JUNIPER-MAC-MIB (mib-jnx-mac), JUNIPER-MAG-MIB (mib-jnx-mag), JUNIPER-MBG-SMI (mib-jnx-mbg-smi), JUNIPER-MIMSTP-MIB (mib-jnx-mimstp), JUNIPER-MOBILE-GATEWAY-AAA-MIB (mib-jnx-mobile-gateway-aaa), JUNIPER-MOBILE-GATEWAY-DHCP-MIB (mib-jnx-mobile-gateway-dhcp), JUNIPER-MOBILE-GATEWAY-EXAMPLE-MIB (mib-jnx-mobile-gateway-example), JUNIPER-MOBILE-GATEWAY-GTP-MIB (mib-jnx-mobile-gateway-gtp), JUNIPER-MOBILE-GATEWAY-RMPS-MIB (mib-jnx-mobile-gateway-rmps), JUNIPER-MOBILE-GATEWAY-SGW-GTP-MIB (mib-jnx-mobile-gateway-sgw-gtp), JUNIPER-MOBILE-GATEWAY-SGW-SM-MIB (mib-jnx-mobile-gateway-sgw-sm), JUNIPER-MOBILE-GATEWAY-SM-IP-POOL-MIB (mib-jnx-mobile-gateway-sm-ip-pool), JUNIPER-MOBILE-GATEWAY-SM-MIB (mib-jnx-mobile-gateway-appfw), JUNIPER-MOBILE-GATEWAYS (mib-jnx-mobile-gateways), JUNIPER-MOBILE-GW-SGW-MFWD-MIB (mib-jnx-mobile-gateway-sgw-mfwd), JUNIPER-MOBILITY-CHARGING-MIB (mib-jnx-mobile-gateway-charging), JUNIPER-MOBILITY-SGW-CHARGING-MIB (mib-jnx-mobile-gateway-sgw-charging), JUNIPER-MPLS-LDP-MIB (mib-jnx-mpls-ldp), JUNIPER-NAT-MIB (mib-jnx-sp-nat), JUNIPER-OAM-MIB (mib-jnx-oam), JUNIPER-OTN-MIB (mib-jnx-otn), JUNIPER-PAE-EXTENSION-MIB (mib-jnx-pae-extension), JUNIPER-PFE-MIB (mib-jnx-pfe), JUNIPER-PING-MIB (mib-jnx-ping), JUNIPER-PMon-MIB (mib-jnx-pmon), JUNIPER-POWER-SUPPLY-UNIT-MIB (mib-jnx-power-supply-unit), JUNIPER-PW-ATM-MIB (mib-jnx-pwatm), JUNIPER-PW-TDM-MIB (mib-jnx-pwtdm), JUNIPER-RMON-MIB (mib-jnx-rmon), JUNIPER-RPF-MIB (mib-jnx-rpf), JUNIPER-RPM-MIB (mib-jnx-rpm), JUNIPER-RPS-MIB (mib-jnx-rps), JUNIPER-RSVP-MIB (mib-jnx-rsvp), JUNIPER-RTM-MIB (mib-jnx-rtm), JUNIPER-SCU-MIB (mib-jnx-scu), JUNIPER-SECURE-ACCESS-PORT-MIB (mib-jnx-secure-access-port), JUNIPER-SIP-COMMON-MIB (mib-jnx-sipcommon), JUNIPER-SNMP-SET-MIB (mib-jnx-gen-set), JUNIPER-SOAM-PM-MIB (mib-jnx-soam-pm), JUNIPER-SONET-MIB (mib-jnx-sonet), JUNIPER-SP-MIB (mib-jnx-sp), JUNIPER-SRX5000-SPU-MONITORING-MIB (mib-jnx-js-spu-monitoring), JUNIPER-SUBSCRIBER-MIB (mib-jnx-subscriber), JUNIPER-SYSLOG-MIB (mib-jnx-syslog), JUNIPER-Services-MIB (mib-jnx-services), JUNIPER-TIMING-NOTFNS-MIB (mib-jnx-timing-notifications), JUNIPER-TRACEROUTE-MIB (mib-jnx-traceroute), JUNIPER-TWAMP-MIB (mib-jnx-rpm-twamp), JUNIPER-USER-AAA-MIB (mib-jnx-user-aaa), JUNIPER-UTIL-MIB (mib-jnx-util), JUNIPER-VIRTUALCHASSIS-MIB (mib-jnx-virtualchassis), JUNIPER-VLAN-MIB (mib-jnx-vlan), JUNIPER-VMON-MIB (mib-jnx-vmon), JUNIPER-VPN-MIB (mib-jnx-vpn), L2L3-VPN-MCAST-MIB (mib-jnx-l2l3vpn-mcast), LLDP-MIB, MCAST-VPN-MIB (mib-jnx-mvpn), MPLS-MIB (mib-jnx-mpls), MPLS-VPN-MIB, OSPFV3-MIB-JUNIPER (mib-jnx-ospfv3mib), VPLS-BGP-DRAFT-01-MIB (mib-jnx-vpls-bgp), VPLS-GENERIC-DRAFT-01-MIB (mib-jnx-vpls-generic), VPLS-LDP-DRAFT-01-MIB (mib-jnx-vpls-ldp)
Pre-compiled MIBs borrowed:
Up to date MIBs: ALARM-MIB, APS-MIB, ATM-MIB, ATM-TC-MIB, BGP4-MIB, BRIDGE-MIB, DIFFSERV-DSCP-TC, DIFFSERV-MIB, DISMAN-PING-MIB, HCNUM-TC, HOST-RESOURCES-MIB, IANA-ADDRESS-FAMILY-NUMBERS-MIB, IANA-RTPROTO-MIB, IANAifType-MIB, IF-MIB, INET-ADDRESS-MIB, INTEGRATED-SERVICES-MIB, IP-FORWARD-MIB, IP-MIB, IPMROUTE-STD-MIB, IPV6-MIB, IPV6-TC, JUNIPER-COS-MIB, JUNIPER-IF-ACCOUNTING-MIB, JUNIPER-IF-MIB, JUNIPER-MIB, JUNIPER-SMI, MPLS-LSR-STD-MIB, MPLS-TC-STD-MIB, MPLS-TE-STD-MIB, OSPF-MIB, P-BRIDGE-MIB, PerfHist-TC-MIB, Q-BRIDGE-MIB, RFC-1212, RFC-1215, RFC1155-SMI, RFC1213-MIB, RMON-MIB, RMON2-MIB, SNMP-FRAMEWORK-MIB, SNMPv2-CONF, SNMPv2-MIB, SNMPv2-SMI, SNMPv2-TC, VPN-TC-STD-MIB
Missing source MIBs:
Ignored MIBs:
Failed MIBs:

動作確認

Juniperの拡張MIBを取得できるようになったことを確認する。
vSRXのシリアルナンバー(OID:jnxBoxSerialNo)を取得してみる

In [1]: from  pysnmp.hlapi import *
In [22]: get =  getCmd(SnmpEngine(),
    ...: CommunityData("community"), 
    ...: UdpTransportTarget((ipaddress, 161)),
    ...: ContextData(),
    ...: ObjectType(ObjectIdentity("JUNIPER-MIB", "jnxBoxSerialNo", 0)))
    
In [23]: serial = next(get)
In [24]: serial
Out[24]:
(None,
 0,
 0,
 [ObjectType(ObjectIdentity(<ObjectName value object at 0x7fb32b2d1b38 tagSet <TagSet object at 0x7fb33341b0f0 tags 0:0:6> payload [1.3.6.1.4.1.2636.3.1.3.0]>), <DisplayString value object at 0x7fb32b2dc780 tagSet <TagSet object at 0x7fb333412c50 tags 0:0:4> subtypeSpec <ConstraintsIntersection object at 0x7fb330075a58 consts <ValueSizeConstraint object at 0x7fb3333c5630 consts 0, 65535>, <ValueSizeConstraint object at 0x7fb32b75e0b8 consts 0, 255>, <ValueSizeConstraint object at 0x7fb330075a20 consts 0, 255>> encoding iso-8859-1 payload [9614550D7979]>)])

In [31]: print(serial[3][0][1])
9614550D7979

※念のためvSRX側でCLIで確認

root> show chassis hardware
Hardware inventory:
Item             Version  Part number  Serial number     Description
Chassis                                9614550D7979      VSRX
CB 0
Routing Engine 0          BUILTIN      BUILTIN           VSRX-S
FPC 0            REV 07   611-049549   RL3714040884      FPC
  PIC 0                   BUILTIN      BUILTIN           VSRX DPDK GE