Bridge Domains; Split-Horizon - Cisco 3845 - Security Bundle Router Software Manual

Understanding EVC Features
Note The switch does not allow overlapping encapsulation configurations. See the
Configurations" section on page

Bridge Domains

A service instance must be attached to a bridge domain. Flooding and communication behavior of a
bridge domain is similar to that of a VLAN domain. Bridge-domain membership is determined by which
service instances have joined it (based on encapsulation criteria), while VLAN domain membership is
determined by the VLAN tag in the packet.
Note You must configure encapsulation before you can configure the bridge domain.
Use the bridge-domain bridge-id service-instance configuration mode command to bind the EFP to a
bridge domain instance. The bridge-id is the identifier for the bridge domain instance, an integer from 1
to 8000.
IGMP snooping is enabled by default on the switch and on all VLANs but is automatically disabled on
a VLAN when you configure a bridge domain under 4094.
The switches support up to 8000 bridge domains on the highest end platform and license.

Split-Horizon

The split-horizon feature allows service instances in a bridge domain to join groups. Service instances
in the same bridge domain and split-horizon group cannot forward data between each other, but can
forward data between other service instances that are in the same bridge domain, but not in the same
split-horizon group.
Service instances do not have to be in a split-horizon group. If a service instance does not belong to a
group, it can send and receive from all ports within the bridge domain. A service instance cannot join
more than one split-horizon group.
Enter the bridge-domain bridge-id split-horizon group group_id service-instance configuration mode
command to configure a split-horizon group. The group_id is an integer from 0 to 2. All members of the
bridge-domain that are configured with the same group_id are part of the same split-horizon group.EFPs
that are not configured with an explicit group_id do not belong to any group.
You can configure no more than 64 service instances per bridge domain. When a bridge domain contains
a service instance that is part of a split-horizon group, this decreases the number of service instances
allowed to be configured in that split-horizon group. The switch supports up to three split-horizon groups
plus the default (no group).
In Table
the indicated split horizon group. Therefore, if a service instance joins split-horizon group 2, it can have
no more than 16 members in split horizon group 2 in the same bridge domain. We recommend that you
add split horizon groups in numerical order to maximize the number of service instances that can belong
to a group.
Cisco ME 3800X and 3600X Switch Software Configuration Guide
11-6
11-13.
11-2, the left column means that a bridge domain belongs to a service instance that is part of
Chapter 11 Configuring Ethernet Virtual Connections (EVCs)
"Examples of Unsupported
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