How Xrn Interacts With Other Features; Vlans - 3Com 5500-SI Configuration Manual

How XRN Interacts
with other Features

VLANs

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.

How XRN Interacts with other Features

VLAN 1
Switch 5500 units
802.3ad
Aggregated Link
VLAN ID 1, 2
XRN Distributed Fabric
VLAN2
VLAN ID 1, 2
681