Broadcom Gigabit Ethernet Teaming Services
NetXtreme
User Guide
Broadcom
®
April 2017 • 2CS57XX-CDUM514-R
Page 107
When the clients and the system are on different subnets, and incoming traffic has to traverse a router, the
received traffic destined for the system is not load balanced. The physical adapter that the intermediate driver
has selected to carry the IP flow carries all of the traffic. When the router sends a frame to the team IP address,
it broadcasts an ARP request (if not in the ARP cache). The server software stack generates an ARP reply with
the team MAC address, but the intermediate driver modifies the ARP reply and sends it over a particular physical
adapter, establishing the flow for that session.
The reason is that ARP is not a routable protocol. It does not have an IP header and therefore, is not sent to the
router or default gateway. ARP is only a local subnet protocol. In addition, since the G-ARP is not a broadcast
packet, the router will not process it and will not update its own ARP cache.
The only way that the router would process an ARP that is intended for another network device is if it has Proxy
ARP enabled and the host has no default gateway. This is very rare and not recommended for most applications.
Transmit traffic through a router will be load balanced as transmit load balancing is based on the source and
destination IP address and TCP/UDP port number. Since routers do not alter the source and destination IP
address, the load balancing algorithm works as intended.
Configuring routers for Hot Standby Routing Protocol (HSRP) does not allow for receive load balancing to occur
in the adapter team. In general, HSRP allows for two routers to act as one router, advertising a virtual IP and
virtual MAC address. One physical router is the active interface while the other is standby. Although HSRP can
also load share nodes (using different default gateways on the host nodes) across multiple routers in HSRP
groups, it always points to the primary MAC address of the team.
Generic Trunking
Generic Trunking is a switch-assisted teaming mode and requires configuring ports at both ends of the link:
server interfaces and switch ports. This is often referred to as Cisco Fast EtherChannel or Gigabit EtherChannel.
In addition, generic trunking supports similar implementations by other switch OEMs such as Extreme Networks
Load Sharing and Bay Networks or IEEE 802.3ad Link Aggregation static mode. In this mode, the team
advertises one MAC Address and one IP Address when the protocol stack responds to ARP Requests. In
addition, each physical adapter in the team uses the same team MAC address when transmitting frames. This
is possible since the switch at the other end of the link is aware of the teaming mode and will handle the use of
a single MAC address by every port in the team. The forwarding table in the switch will reflect the trunk as a
single virtual port.
In this teaming mode, the intermediate driver controls load balancing and failover for outgoing traffic only, while
incoming traffic is controlled by the switch firmware and hardware. As is the case for Smart Load Balancing, the
BASP intermediate driver uses the IP/TCP/UDP source and destination addresses to load balance the transmit
traffic from the server. Most switches implement an XOR hashing of the source and destination MAC address.
Summary of Contents for NetXtreme BCM57 Series
Page 1: ...Broadcom NetXtreme BCM57XX User Guide Last revised April 2017 2CS57XX CDUM514 R...
Page 16: ...Functionality and Features NetXtreme User Guide Broadcom April 2017 2CS57XX CDUM514 R Page 16...
Page 169: ...Regulatory Information NetXtreme User Guide Broadcom April 2017 2CS57XX CDUM514 R Page 169...
Page 170: ...Regulatory Information NetXtreme User Guide Broadcom April 2017 2CS57XX CDUM514 R Page 170...
Page 171: ...Regulatory Information NetXtreme User Guide Broadcom April 2017 2CS57XX CDUM514 R Page 171...
