Deployment Guide
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, 56 ports.
The last stack unit is assigned eight pairs, the eight pair is unused.
The rst 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 rst 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 rst hex pair changes from 00 to 04.
Example of Viewing VLAN Ports Using SNMP (Port Assigned)
[Dell Networking system output]
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 Tengig 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
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 value 40 is in the rst 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.
Fetching Dynamic MAC Entries using SNMP
The Aggregator supports the RFC 1493 dot1d table for the default VLAN and the dot1q table for all other VLANs.
NOTE
: The table contains none of the other information provided by the show vlan command, such as port speed or whether the
ports are tagged or untagged.
NOTE: The 802.1q Q-BRIDGE MIB denes VLANs regarding 802.1d, as 802.1d itself does not dene them. As a switchport must
belong a VLAN (the default VLAN or a congured VLAN), all MAC address learned on a switchport are associated with a VLAN.
For this reason, the Q-Bridge MIB is used for MAC address query. Moreover, specic to MAC address query, the MAC address
indexes dot1dTpFdbTable only for a single forwarding database, while dot1qTpFdbTable has two indices — VLAN ID and MAC
address — to allow for multiple forwarding databases and considering that the same MAC address is learned on multiple VLANs.
The VLAN ID is added as the rst index so that MAC addresses are read by the VLAN, sorted lexicographically. The MAC address
is part of the OID instance, so in this case, lexicographic order is according to the most signicant octet.
Simple Network Management Protocol (SNMP) 219