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9-3
Cisco 10000 Series Router Service Selection Gateway Configuration Guide
OL-4387-02
Chapter 9 Interface Configuration
Multicast Protocols on SSG Interfaces
Network Side Interfaces
For network side interfaces, SSG uplink interfaces can accept and forward both SSG traffic and
transparent passthrough traffic. The SSG software classifies the traffic as transparent passthrough. An
interface that is not configured as an SSG uplink can receive transparent passthrough traffic or traffic
destined for Cisco IOS interfaces. The traffic is handled using normal Cisco IOS processing.
Typically, SSG uses transparent passthrough access control lists (ACLs) to allow unauthenticated traffic
to be routed through normal Cisco IOS processing. However, the Cisco 10000 series router does not
require transparent passthrough ACLs (see the “Restrictions of Transparent Passthrough” section on
page 9-3).
The following Cisco-AV pair attributes are used to configure transparent passthrough ACLs:
• Downstream Access Control List (outacl)—Specifies either a Cisco IOS standard ACL or an
extended ACL to be applied to downstream traffic going to the user.
• Upstream Access Control List (inacl)—Specifies either a Cisco IOS standard ACL or an extended
ACL to be applied to upstream traffic coming from the user.
For more information about transparent passthrough ACLs, refer to the Service Selection Gateway,
Release 12.2(15)B feature module.
Restrictions of Transparent Passthrough
SSG uplink interfaces can accept and forward both SSG traffic and transparent passthrough traffic.
Typically, transparent passthrough ACLs are used to prevent downstream SSG traffic from being
forwarded by Cisco IOS software. However, the Cisco 10000 series router does not require transparent
passthrough ACLs; therefore, SSG hosts that have not been authorized for specific services might be able
to receive traffic from those services. If the host attempts to send traffic, the packets are dropped until
authentication occurs.
Configuration of Transparent Passthrough
Transparent passthrough is always enabled for SSG VRFs for uplink interfaces.
Multicast Protocols on SSG Interfaces
SSG supports multicast traffic, which includes normal multicast packets and Internet Group
Management Protocol (IGMP) packets. The multicast traffic is separate from the SSG traffic and is
routed through normal Cisco IOS processing and features; it is not routed through SSG authentication
or features such as per-service statistics or hierarchical policing.
SSG interfaces can simultaneously receive multicast traffic and normal SSG traffic such as traffic to and
from the default network, Open Garden network, and service networks. The normal SSG traffic is routed
through SSG features and processing.