Fujitsu BX600 SB9 manual Port Aggregation, Network problems

White Paper ⏐ Issue: October 2006 ⏐ Integration of BX600 SB9 Switches in Cisco Networks Page 5 / 47

2.2Port Aggregation

2.2.1 Introduction

You will usually need more than 1 Gbit when connecting an SB9 switch in a datacenter. In this case two or more links are set up to form a port-channel, also known as a Fast Ethernet Channel (FEC) or Gigabit Ethernet Channel (GEC) in Cisco networks. Figure 1 shows a typical uplink configuration for an SB9: One port-channel connects to Cisco switch A and a second one connects to Cisco switch B. Each port-channel is formed of two links running with 1000 Mbit in full duplex mode. The redundancy mechanisms between these links will be discussed later. In principle, port-channels can be configured statically or using a port aggregation protocol. Cisco supports LACP as specified in 802.3ad and their proprietary PagP, while the SB9 supports LACP as specified in 802.3ad.

Using static or LACP dynamic configuration, you can form up to six GE links between the SB9 and one other switch.

Figure 1 : Typical uplink configuration for SB9

Table 2 shows the possible combinations of port-channel settings between SB9 and Cisco switches. The combinations marked red are very risky and would lead to networks loops.

No channel

SB9

No Channel	LACP	Static
OK	OK	!!!

Cisco	Passive	OK	OK	!!!
	Active	OK	OK	!!!
	On	!!!	!!!	OK

Table 2 : Possible port-channel configurations

So called “split channels”; where one channel from one switch is terminated at two other switches; are supported neither by the SB9 nor by Cisco switches.

2.2.2 Recommended Solution

Although Cisco switches and SB9 both support LACP, and although this feature has been tested to be compatible between these devices, we recommend using static configured trunks. This is the best practice to minimize the risk of incompatibilities and misconfigurations.

Caution:	In order to avoid loops in the network, please be sure that the affected ports of a port-channel are shut
	down during the configuration process. Generating loops in a datacenter network may cause serious
	network problems!