Dell PowerConnect B-FCXs, Configuration Manual

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1356 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
DHCP relay agent information (DHCP Option 82)
39
Sub-option 1 – circuit id
The Circuit ID (CID) identifies the circuit or port from which a DHCP client request was sent. The
PowerConnect switch uses this information to relay DHCP responses back to the proper circuit, for
example, the port number on which the DHCP client request packet was received.
Dell PowerConnect devices support the General CID packet format . This simple format encodes
the CID type, actual information length, VLAN ID, slot number, and port number. This format is
compatible with the format used by other vendors’ devices.
Figure 180 illustrates the general CID
packet format.
FIGURE 180 General CID packet format
Sub-option 2 – Remote ID
The Remote ID (RID) identifies the remote host end of the circuit (the relay agent). Dell
PowerConnect devices use the MAC address to identify itself as the relay agent.
Figure 181
illustrates the RID packet format.
FIGURE 181 RID packet format
Sub-option 6 - subscriber id
The Subscriber ID (SID) is a unique identification number that enables an Internet Service Provider
to:
•
Identify a subscriber
•
Assign specific attributes to that subscriber (for example, host IP address, subnet mask, and
domain name server (DNS))
•
Trigger accounting
Figure 182 illustrates the SID packet format.
FIGURE 182
SID packet format
The second byte ( N in Figure 182 ) is the length of the ASCII string that follows. The PowerConnect
switch supports up to 50 ASCII characters.
1 Byte 2 Byte s
1 6 0 4 VLAN ID Slot ID Port
1 Byte
2 8 0 6
MAC Addre ss
1 Byte
6 N ASCII String 1.....N