Cisco ASR 9000 Series System Configuration Guide

◦ Hop Count – This only affects simple rings, and provides a default traffic engineering algorithm
based on number of intervening Satellite devices.
◦ Parity of the Satellite ID – This is used as a late tie breaker to provide some load balancing across
two Hosts with numerous hub-and-spoke Satellites, in which the even-numbered Satellites prefer
one host, while the odd-numbered Satellites prefer the other host.
On a tie-breaker of all the previous priorities, it falls back to the Primary host, which is the one with the
lowest chassis MAC address based on byte size.
• Support for seamless Split Brain handling — A Split Brain is a condition in which the two hosts are
no longer able to communicate with each other, but each of them can still communicate with the Satellite
device. This scenario can be hazardous, because the devices can reach different conclusions, resulting
in traffic loss, or loops and broadcast storms.
The Satellite protocol has these features to cope with such a situation:
◦
When connected to each other, the two hosts publish a shared System MAC. This allows the
Satellites to recognize probes from what appear to be different hosts, but in fact come from a paired
set of hosts.
◦
Whenever a host-to-host connection is lost, each peer publishes the Chassis MAC as the System
MAC. This operation is seamless and does not require a reset of the state machines, and hence
causes no traffic loss. This allows the Satellite to react, most likely by dropping its connection to
the standby host.
◦
Whenever the connection is restored, the hosts again start publishing the System MAC seamlessly
and allowing the Satellite to restore functionality to the standby host.
◦
If the host-to-host connection is lost while the host is PE-isolated, it immediately drops discovery
to the satellite. This ensures that the satellite uses the host with an available path to the core, if one
exists.
Soft Minimum Active Links for Dual Home Topology
The Soft minimum active links feature for dual home network topology allows you to configure a minimum
number of active links in a bundle satellite-fabric-link. Hence, in a Dual Home setup, if the number of active
links to the active host is less than the configured minimum due to any failure on member links, then the
satellite failover to the standby host. When soft minimum active links is configured, failover is executed if
another suitable host is available or else the traffic is left unaffected. In the case where both the active and
standby hosts have less active links than the configured values, then no switch over occurs.
If a split brain event occurs followed by the number of active links on the active host dropping below the
configured amount, then the satellite does not failover unless there are no active links remaining.
Note
General Limitations of Satellite nV System Network Topologies
1
A satellite can be connected to only one Host in the Hub and Spoke topology model and can be connected
to only two hosts in a Dual-homed network architecture.
Cisco ASR 9000 Series Aggregation Services Router nV System Configuration Guide, Release 5.3.x
13
Configuring the Satellite Network Virtualization (nV) System
Soft Minimum Active Links for Dual Home Topology

Cisco ASR 9000 Series Specifications

General

Brand	Cisco
Model	ASR 9000 Series
Category	Network Router
Language	English