3com 5500-SI Manual De Usuario

This section provides supplementary information on how XRN interacts with other 
software features supported by your Switch.

Figure 181 shows a single aggregated link, created automatically using LACP, 
connecting the Switch 5500 stack to the Distributed Fabric. The Distributed Fabric 
will take its VLAN membership from a port within the Switch

 

5500 stack . 

If the Fabric Interconnect fails the aggregated link will split, creating two separate 
aggregated links (as shown in Figure 182). If the ports within the Switch 5500 
stack each have different VLAN membership, this will mean the two newly formed 
aggregated links will also have different VLAN membership. This will result in the 
different VLANs not being able to communicate. 

3Com recommends that you set individual ports that are to be members of an 
aggregated link to the same VLAN membership. This ensures communication 
between all VLANs at all times.

Figure 181   How XRN interacts with VLANs—Example 1

The Distributed Resilient Routing (DRR) feature also requires that all units can 
communicate with each other on all VLANs. This ensures that on an interconnect 
failure all units can communicate with each other. 

For example in Figure 182 the interconnect has failed and only one of the units in 
the Distributed Fabric will act as the router. STP will detect a potential loop and 
block a path of its choosing, in this example it has blocked the path between 
Switch X units and Switch A. If ports have different VLAN membership as shown 
here there will be loss of communication between VLANs 1 and 2.

VLAN2

VLAN 1

Switch 5500 units

XRN Distributed Fabric

802.3ad

Aggregated Link

VLAN ID 1, 2

VLAN ID 1, 2