Cisco 6500 User Manual
Page 7
4-7
Cisco IOS Software Configuration Guide, Release 12.2SX
OL-13013-06
Chapter 4 Configuring Virtual Switching Systems
Understanding Virtual Switching Systems
VSS Quad-Sup Uplink Forwarding
When you use VSS quad-supervisor uplink forwarding, the in-chassis standby (ICS) supervisor engine
acts as a DFC line card. Only one processor, the SP processor, acts as the DFC line card; the RP processor
is reset to ROMMON. During the bootup, once the chassis level role is resolved, the ICS downloads the
image from the in-chassis active (ICA) supervisor engine. Once the supervisor engine is booted with the
image, it will function in the same way as a DFC line card. All applications running in virtual switch
(VS) view the in-chassis standby as a DFC line card.
See
for the various roles that supervisor engines can assume within a quad-supervisor VSS
system.
Figure 4-5
Typical VSS Quad-Supervisor Configuration
If your supervisor engine is:
•
in-chassis active, it can be VSS active or VSS standby.
•
in-chassis standby, it can only be an ICS.
•
VSS active, it can only be ICA.
•
VSS standby, it can only be ICA.
Quad-supervisor uplink forwarding provides these key features:
•
eFSU upgrades— You can upgrade or downgrade your VSS system using ISSU. See
for more information about eFSU upgrades.
•
Image version mismatch—Before the bootup, the ICS completes a version check. If there is a
version mismatch, the ICS is set to ROMMON. If you want to boot different images on the ICS and
ICA. You need to configure the no switch virtual in-chassis standby bootup version
mismatch-check command. This command is only valid once all four supervisors are running
software that supports Quad-supervisor uplink forwarding. If one supervisor is running software that
does not support Quad-supervisor uplink forwarding the command will have no effect.
•
EARL mode mismatch—If the supervisor engine EARL modes do not match then the supervisor
engine is reset to ROMMON. It is recommended that all four supervisor engines run the same EARL
Lite or EARL Heavy version.
•
VSS RPR switchover—On RPR switchover the ICS will be reset. For more information regarding
RPR see
“RPR and SSO Redundancy” section on page 4-12
.
Linecard 1
Linecard 2
Linecard N
Supervisor 2:
standby, ICA
Supervisor 3 ICS
Supervisor 4 ICS
Linecard 1
Linecard 2
Linecard N
Supervisor 1:
active, ICA
197277
VSL
Active chassis
Standby chassis