3Com 5500-SI Configuration Manual page 679

Figure 180 A Dual XRN Distributed Fabric Network
How to Set up this Network
This section provides information on how to configure an XRN network as shown
in Figure 180. It assumes you have carried out step 1 to step 4 as detailed in "How
to Implement XRN—Overview" on page 676.
1 Enable LACP on the required ports, ensuring you have not connected your devices
to the Distributed Fabric yet as you must configure your VLANs before the
aggregated links are configured. Individual port members of each aggregated link
must have VLAN membership explicitly set, that is, manually configured, before
the aggregated link is set up. You must not rely on port members inheriting VLAN
membership configuration from the aggregated link.
2 Create the VLANs and assign VLAN membership to all ports.
3 Connect up your ports. As LACP was enabled in step 1 the aggregated links will
now automatically configure themselves.
4 Configure the router IP interfaces.
5 Ensure that RSTP is enabled across the network.
Legacy aggregated links are not resilient to an interconnect failure. Hence the
3Com recommendation to use IEEE 802.3ad aggregated links (LACP) for maximum
resilience.
If an automatic aggregated link (created by LACP) contains ports with different
VLAN membership, the aggregated link will inherit the VLAN membership of the
first port that comes up in the aggregated link. It will override any pre-defined
VLAN membership for the aggregated link.
VLAN 1 VLAN2
XRN Distributed Fabric
802.3ad
Aggregated Links
VLAN ID 1, 2
VLAN ID 1, 2
XRN Distributed Fabric
Servers on
1000 Mbps connections
Network Example using XRN
VLAN 1 VLAN2
Switch 5500 units
VLAN ID 1, 2
VLAN ID 1, 2
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