Cisco Cisco 1700 2600 3600 3700 Series VPN Module White Paper
© 2012 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.
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Typically, in a standalone environment, these First Hop Redundancy Protocols (FHRPs) are required to provide a
single default gateway that is both redundant and highly available. These protocols typically designate an active
forwarder for a given pair of Layer 3 interfaces by using respective hello protocols. Additionally, a separate
instance of these hello protocols is run for each pair of interfaces for which the FHRP is configured.
In a Cisco Virtual Switching System environment, the use of FHRPs to provide default gateway redundancy has
been obviated in most environments, because a single interface and router MAC address are shared across both
virtual switches (Figure 20).
Figure 20. First Hop Redundancy Protocols
You can enable FHRP to another network device or Cisco Virtual Switching System with the FHRP frames
redirected to the route processor of the active virtual switch for processing.
Failure Scenarios
With the VSS operating under normal, non-failure scenarios both chassis are actively forwarding data traffic, while
one of the supervisor modules has negotiated to become the active control plane.
Active Supervisor Engine Failure
The standby supervisor engine can detect the failure of the active supervisor engine using one of the following
methods:
Redundancy framework heartbeats sent across the VSL:
●
VSL Protocol (VSLP)
●
Cisco Generic Online Diagnostics (GOLD) failure event
●
CDL-based hardware assistance
●
Full VSL link down
Upon detecting the failure of the active supervisor, the hot-standby supervisor engine performs an SSO switchover
and assumes the role of the active supervisor. An online insertion and removal (OIR) event is simulated for all
modules in the previous active chassis to remove those cards from the running chassis inventory.
5
5
If there is an in-chassis redundant supervisor engine installed or if the failed supervisor is capable of performing a reload, the
failed chassis will be reloaded. After the reload, the former in-chassis standby supervisor will assume the role of the in-chassis
active supervisor and proceed to boot chassis. This chassis will then become the VSS Hot Standby.
active supervisor and proceed to boot chassis. This chassis will then become the VSS Hot Standby.