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Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

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Displaying the Ports in a VLAN using SNMP

Dell Networking OS identifies VLAN interfaces using an interface index number that is displayed in the output of the show interface vlan command.

Example of Identifying the VLAN Interface Index Number 

Dell(conf)#do show interface vlan id 10
                                 % Error: No such interface name.
                                 R5(conf)#do show interface vlan 10
                                 Vlan 10 is down, line protocol is down
                                 Address is 00:01:e8:cc:cc:ce, Current address is 00:01:e8:cc:cc:ce
                                 Interface index is 1107787786
                                 Internet address is not set
                                 MTU 1554 bytes, IP MTU 1500 bytes
                                 LineSpeed auto
                                 ARP type: ARPA, ARP Timeout 04:00:00

To display the ports in a VLAN, send an snmpget request for the object dot1qStaticEgressPorts using the interface index as the instance number, as shown in the following example.

Example of Viewing the Ports in a VLAN in SNMP 

snmpget -v2c -c mycommunity 10.11.131.185 .1.3.6.1.2.1.17.7.1.4.3.1.2.1107787786
                                 SNMPv2-SMI::mib-2.17.7.1.4.3.1.2.1107787786 = Hex-STRING:
                                 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                                 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                                 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
The table that the Dell Networking system sends in response to the snmpget request is a table that contains hexadecimal (hex) pairs, each pair representing a group of eight ports.
  • Seven hex pairs represent a stack unit. Seven pairs accommodate the greatest number of ports available on an Aggregator, 12 ports. The last stack unit is assigned eight pairs, the eight pair is unused.
The first hex pair, 00 in the previous example, represents ports 1 to 7 in Stack Unit 0. The next pair to the right represents ports 8 to 15. To resolve the hex pair into a representation of the individual ports, convert the hex pair to binary. Consider the first hex pair 00, which resolves to 0000 0000 in binary:
  • Each position in the 8-character string is for one port, starting with Port 1 at the left end of the string, and ending with Port 8 at the right end. A 0 indicates that the port is not a member of the VLAN; a 1 indicates VLAN membership.

All hex pairs are 00, indicating that no ports are assigned to VLAN 10. In the following example, Port 0/2 is added to VLAN 10 as untagged; the first hex pair changes from 00 to 04.

Example of Viewing VLAN Ports Using SNMP (Port Assigned) 

R5(conf)#do show vlan id 10
                                 
                                 Codes: * - Default VLAN, G - GVRP VLANs
                                 Q: U - Untagged, T - Tagged
                                 x - Dot1x untagged, X - Dot1x tagged
                                 G - GVRP tagged, M - Vlan-stack
                                 
                                 NUM Status  Description  Q Ports
                                 10  Inactive             U TenGi 0/2
                                 
                                 [Unix system output]
                                 
                                 > snmpget -v2c -c mycommunity 10.11.131.185 .1.3.6.1.2.1.17.7.1.4.3.1.2.1107787786
                                 SNMPv2-SMI::mib-2.17.7.1.4.3.1.2.1107787786 = Hex-STRING: 40 00 00 00 00 00 00 00 00 00 00

The value 40 is in the first set of 7 hex pairs, indicating that these ports are in Stack Unit 0. The hex value 40 is 0100 0000 in binary. As described, the left-most position in the string represents Port 1. The next position from the left represents Port 2 and has a value of 1, indicating that Port 0/2 is in VLAN 10. The remaining positions are 0, so those ports are not in the VLAN.

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