modifications to the designated Echo Node were required. Third, a frame type had to be
chosen that would not cause loss of communication for normal data traffic between the Echo
Node and the team since, in many environments, the Echo Node could be another server,
another client, a switch, or a router functioning as the team’s gateway.
To comply with the above requirements, Directed ARP was designed to use a modified ARP
request frame as the Echo Node probe. The format of the ARP request frame was chosen in
order to prevent Echo Node probes from changing the team’s ARP cache entry in the Echo
Node’s ARP table. By omitting the Source IP address in the ARP frame, the designated Echo
Node doesn’t have enough information to modify its ARP entry for the team’s IP address.
However, the Echo Node will respond back to the Source MAC address in the ARP frame
with an ARP response. Since each teamed port inserts its own unique MAC address in the
Source MAC Address field, each teamed port receives an individual response from the Echo
Node. As a result, Directed ARP’s Echo Node probe provides for validation to each teamed
port, works with most (but not all) IP protocol stacks, and does not cause loss of
communication with the team for normal data traffic.
Table 4-3 Directed ARP Echo Node Probe REQUEST Frame Format
64 Bytes TotalValueEthernet V2 Frame Format
6 bytes“Broadcast” unless specified in GUIDestination MAC address
6 bytes“MAC address of Teamed port”Source MAC address
4 bytes“Value of VLAN ID and Priority”802.1Q/p tag (optional)
2 bytes0x0806 (ARP)Type
2 bytes0x01 (Ethernet)Hardware type
2 bytes0x800 (IP)Protocol type
1 byte0x06Hardware address length
1 byte0x04Protocol address length
2 bytes0x001 (ARP request)ARP operation
6 bytes“MAC address of Teamed port”Source MAC address
4 bytes0.0.0.0Source IP address
6 bytes00:00:00:00:00:00Destination MAC address
4 bytes“Echo Node IP Address from GUI”Destination IP address
4 bytes“varies”Checksum
Table 4-4 Directed ARP Echo Node Probe REPLY Frame Format
64 Bytes TotalValueEthernet V2 Frame Format
6 bytes“MAC address of Teamed port”Destination MAC address
6 bytes“Echo Node’s MAC Address”Source MAC address
4 bytes“Value of VLAN ID and Priority”802.1Q/p tag (optional)
2 bytes0x0806 (ARP)Type
2 bytes0x01 (Ethernet)Hardware type
2 bytes0x800 (IP)Protocol type
1 byte0x06Hardware address length
1 byte0x04Protocol address length
40 The Mechanics of Teaming for the Advanced User
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