Route Processor Redundancy and Stateful Switch Over

Route Processor Redundancy

1. Supported from 12.2(12c)EW onwards.

2. Redundant supervisory engine will synchronize itself with the active supervisory engine’s start-up config only, the redundant supervisory engine will be in partial-initialized state until the active supervisory engine fails.

3. During switch over, traffic will be disrupted, this is because only the persistent configuration (start-up configuration in NVRAM) is synchronized, the redundant supervisory engine does not have information about the states of the line cards.

4. Hence when the redundant supervisory engine takes over as active, it boots up and reinitialized information from the modules.


Stateful SwitchOver

1. Redundant supervisory engine is initialized completely and synchronizes start-up and running-configuration with the active supervisory engine, the link states of all line cards will also be synchronized, below protocols will also be synchronized:

i. 802.3

ii. 802.3u

iii. 802.3x (Flow control)

iv. 802.3ab (Gigabit ethernet)

v. 802.3z (Gigabit ethernet including CWDM)

vi. 802.3ad (LACP)

vii. 802.1q

viii. 802.1X (Radius)

ix. 802.1D (STP)

x. 802.3af (PoE)

xi. PAgP

xii. VTP

xiii. Dynamic ARP Inspection

xiv. DHCP snooping

xv. IP Source Guard

xvi. IGMP snooping (version 1 and 2)

xvii. DTP (802.1q and ISL)

xviii. 802.1w (MST)

xix. PVST+

xx. Rapid PVST

xxi. Portfast/uplink fast/backbone fast

xxii. BPDU guard and filtering

xxiii. Voice VLAN

xxiv. Unicast MAC filtering

xxv. ACL (VACL, PACL and RACL)

xxvi. QoS (DBL)

xxvii. Multicast storm control and broadcast storm control

Protocol information not synchronized:

i. 802.1q tunneling

ii. Baby giants.

iii. Jump frame support

iv. CDP

v. Flood control

vi. UDLD


viii. NetFlow

All switch virtual interfaces are synchronized.


RPR synchronization

RPR enabled redundant sup engine is partially initialized, it will only be synchronized when the active sup engine has changed its start-up configuration. Hence for this reason, if user wants to synchronize the redundant sup engine a write command is necessary.

When a second sup engine is inserted into the chassis, active sup engine detects the redundant sup engine and perform synchronization, all existing configuration in redundant sup engine will be replaced.

auto-sync command is enabled by default, when redundant sup engine boots start-up configuration is synchronized.


SSO synchronization

Active sup engine detects the newly inserted sup engine and perform start-up and running configuration synchronization.

Real-time changes that modify the running-config will be synchronized as well.

When write command is used, modification of start-up config will be synchronized as well.


Active and redundant election

First come first served basis, which sup engine boots up first becomes the active. Period.


SSO configuration


Switch(config-red)#mode sso


Things to note on SSO

While SSO CEF table will be cleared, routing will be disrupted until routing protocols converged.

Static routes are preserved.

Layer 3 dynamic states information will be lost on switchover. NSF is needed to preserve dynamic routing information.

Configuration change occurs the same time as switchover, that configuration is lost. Previous configuration will still be preserved.

If a line card is removed on a redundant sup engine and you initiate a switchover, when you reinsert the line card all ports will be shut down, however line card configuration will still be preserved.


Console into the redundant sup engine

Each sup engine has its own console port, to access the redundant sup engine through virtual terminal (console) you have to physically put your roll-over cable into the console port of the redundant sup engine.

You can however access the virtual console of the redundant sup engine from active sup engine using virtual console, this feature can only be used in privilege level 15.

Switch#session module 2

Suppose slot 2 is the redundant sup engine.



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