Cisco SCE 1000 2xGBE User's Guide download pdf (Page 42)

Chapter 2 Topology

Failure and Recovery

SCE 1000 2xGBE Release 2.0.10 User Guide

2-6 OL-7117-02

The above figure represents the SCE 1000 redundant topology. It is applicable as an overlay to a

customer’s redundant topology, on condition that the entire traffic of a specific subscriber (end

station, subnet or VLAN) is flowing through one link only. Both links may be active, providing

that the subscriber traffic is mutually exclusive.

This redundancy solution addresses any failure in the SCE 1000 Platform itself. It is based on the

idea that any fatal hardware or software failure will cause the platform to “cut” the link. A “cut”

link will cause the routers/switches on both ends to switch the traffic to the standby link. On the

standby link, the traffic is analyzed and policies enforced by the standby SCE 1000, which, after

the failure, acts as the active SCE 1000.

Note that when both links are simultaneously independently active and redundant for the other

link (as is the case when HSRP with two virtual routers is used), if one link fails, its traffic is

directed to the other link. However, the overall supported load in the link that is now carrying all

the traffic is only equal to one link, not two.

During setup of this topology, the configuration of the two SCE 1000 platforms is done through

multi-box configuration. This ensures that both hold the same configurations and policies. The

functional operation of switching from the active to standby, SCE 1000 is contingent upon the

fact that the two SCE 1000 platforms are in the same Domain. All configurations performed on

this Domain are automatically updated on both SCE Platforms. Both boxes should also be

assigned to the same Subscriber Domain. For more information on Domains, see the smartSUB

Manager User Guide.

The common protocols used for redundancy traffic switching between network elements such as

routers and switches in networks are Spanning-Tree in layer2, HSRP in layer3 (usually used in

data-centers), and other common routing protocols like OSPF or RIP.

Note

When using routing/switching protocols that perform load balancing as well, the load balancing

capabilities should be disabled.

The transition to the backup SCE 1000 platform is transparent. Once the routers/switches detected

that traffic has been cut, they start sending traffic through the redundant link. After this occurs, the

failed SCE 1000 can be fixed/replaced with no downtime, since the box is effectively

disconnected from the network. After fixing/replacing the failed SCE 1000, you must copy the

configuration of the current active SCE 1000 to the fixed/replaced SCE 1000.

The backup and restore procedures used for copying policies and Service Configurations from

one SCE 1000 to the next are detailed in the Service Control Application Suite for Broadband

User Guide.

Failure and Recovery

It is important to decide how the system should behave in case of the failure of the SCE 1000,

both during the time that the unit is down and after recovery. This decision is influenced by

several factors:

• Physical installation (connection mode)

• Redundancy

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Cisco SCE 1000 2xGBE User's Guide Page 42

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