VLAN to port mapping using SNMP on Juniper EX

This post is about SNMP and it will show you how you can retrieve all the ports that are part of a VLAN and how you can retrieve the vlan membership of a port on a Juniper EX switch.

Before doing this, let’s see what the cli output is and we will compare it with the snmp walk output.

The test will involve VLANs v2220, v2221 and interface ge-0/0/3:

{master:0}
lab@EX4200> show vlans 
Name           Tag     Interfaces
default       
                       None
v2220          2220   
                       ge-0/0/3.0*
v2221          2221   
                       ge-0/0/3.0*

{master:0}
lab@EX4200>

1. To retrieve all ports under a VLAN, follow this procedure:

{master:0}
 lab@EX4200> show snmp mib walk jnxExVlanName
 jnxExVlanName.3 = default
 jnxExVlanName.4 = v2220          ----------> index 4
 jnxExVlanName.5 = v2221

{master:0}
 lab@EX4200> show snmp mib walk jnxExVlanPortStatus.4
 jnxExVlanPortStatus.4.516 = 3

{master:0}
 lab@EX4200> show snmp mib get dot1dBasePortIfIndex.516
 dot1dBasePortIfIndex.516 = 626

{master:0}
 lab@EX4200> show snmp mib get ifDescr.626
 ifDescr.626   = ge-0/0/3.0

{master:0}
 lab@EX4200>

2. To retrieve the VLAN membership of a port, follow this procedure:

{master:0}
 lab@EX4200> show snmp mib walk ifDescr | match ge-0/0/3.0
 ifDescr.626   = ge-0/0/3.0

{master:0}
 lab@EX4200> show snmp mib walk dot1dBasePortIfIndex | match 626
 dot1dBasePortIfIndex.516 = 626

{master:0}
 lab@EX4200> show snmp mib walk jnxExVlanPortStatus | match 516
 jnxExVlanPortStatus.4.516 = 3          ----------> index 4
 jnxExVlanPortStatus.5.516 = 3          ----------> index 5

{master:0}
 lab@EX4200> show snmp mib get jnxExVlanName.4
 jnxExVlanName.4 = v2220

{master:0}
 lab@EX4200> show snmp mib get jnxExVlanName.5
 jnxExVlanName.5 = v2221

{master:0}
 lab@EX4200>

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Paris ARAU

Paris ARAU is a networking professional with strong background on routing and switching technologies. He is a holder of CCIE R&S and dual JNCIE(SP and ENT). The day to day work allows him to dive deeply in networking technologies. Part of the continuously training, he is focusing on Software Defined Network and cloud computing.

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