To avoid traffic interruption, you can enable alternative routes globally to replace the best route with the next-best route, if the best route becomes unavailable.
The concept of alternative route applies between routing protocols. For example, if an OSPFv3 route becomes unavailable and an alternative RIPng route is available, the system activates the RIPng route immediately without waiting for an update interval to expire.
By default, the alternative routes feature is globally enabled on the switch.
The following example demonstrates this behavior.
In this example, you configure OSPFv3 and RIPng routes on two switches, Switch-1 and Switch-2, as shown in the following table.
| Configuration | Switch-1 | Switch-2 |
|---|---|---|
| VLAN ID | 2 | 2 and 3 |
| IPv6 address | 2000:0:0:0:0:0:0:1/64 |
VLAN 2: 2000:0:0:0:0:0:0:2/64 VLAN 3: 3000:0:0:0:0:0:0:2/64 |
| Protocols | OSPFv3 and RIPng | OSPFv3 and RIPng |
| VLAN port members | 1/5 |
VLAN 2: 1/5 VLAN 3: 1/6 |
On Switch-1, configure VLAN 2 and the IPv6 interface address 2000:0:0:0:0:0:0:1/64.
Switch1:1:1>enable Switch1:1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch1:1(config)#vlan create 2 type port-mstprstp 0 Switch1:1(config)#vlan members 2 1/5 Switch1:1(config)#interface vlan 2 Switch1:1(config-if)#ipv6 interface address 2000:0:0:0:0:0:0:1/64 Switch1:1(config-if)#ipv6 interface enable Switch1:1(config-if)#exit
Switch1:1(config)#show vlan basic
=======================================================================================
Vlan Basic
=======================================================================================
VLAN MSTP
ID NAME TYPE INST_ID PROTOCOLID SUBNETADDR SUBNETMASK VRFID ORIGIN
---------------------------------------------------------------------------------------
1 Default byPort 0 none N/A N/A 0 CONFIG
2 VLAN-2 byPort 0 none N/A N/A 0 CONFIG
All 2 out of 2 Total Num of Vlans displayed
Switch1:1>show vlan members
==========================================================================
Vlan Port
==========================================================================
VLAN PORT ACTIVE STATIC NOT_ALLOW
ID MEMBER MEMBER MEMBER MEMBER
--------------------------------------------------------------------------
1 1/1-1/4,1/6- 1/1-1/4,1/6-
1/24 1/24
2 1/5 1/5
All 2 out of 2 Total Num of Port Entries displayed
Switch1:1(config)#show ipv6 interface vlan 2
=================================================================================================================
Vlan Ipv6 Interface
=================================================================================================================
IFINDX VLAN PHYSICAL ADMIN OPER TYPE MTU HOP REACHABLE RETRANSMIT MCAST IPSEC RPC RPCMODE
INDX ADDRESS STATE STATE LMT TIME TIME STATUS
-----------------------------------------------------------------------------------------------------------------
2050 2 b0:ad:aa:4e:59:00 enable up ETHER 1500 64 30000 1000 disable disable disable existonly
=================================================================================================================
Vlan Ipv6 Address
=================================================================================================================
IPV6 ADDRESS VLAN-ID TYPE ORIGIN STATUS NAME
-----------------------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 V-2 UNICAST MANUAL PREFERRED
fe80:0:0:0:b2ad:aaff:fe4e:5900/64 V-2 UNICAST LINKLAYER PREFERRED
1 out of 1 Total Num of Interface Entries displayed.
2 out of 2 Total Num of Address Entries displayed.
Configure port 1/5.
Switch1:1(config)#interface gigabitEthernet 1/5 Switch1:1(config-if)#encapsulation dot1q Switch1:1(config-if)#no shutdown Switch1:1(config-if)#exit
Configure IPv6 globally.
Switch1:1(config)#ipv6 forwarding
Switch1:1(config)#show ipv6 forwarding
Ipv6 forwarding - GlobalRouter : enable
ecmp : disable
ecmp-max-path : 1
Configure OSPFv3 on the VLAN.
Switch1:1(config)#interface vlan 2
Switch1:1(config-if)#ipv6 ospf area 0.0.0.0
Switch1:1(config-if)#ipv6 ospf enable
Switch1:1(config-if)#show ipv6 ospf interface vlan 2
admin-status : enable
area : 0.0.0.0
dead-interval : 40
hello-interval : 10
metric : 1
poll-interval : 120
priority : 1
retransmit-interval : 5
transit-delay : 1
type : BROADCAST
Configure OSPFv3.
Switch1:1(config-if)#exit
Switch1:1(config)#router ospf ipv6-enable
Switch1:1(config)#show ipv6 ospf
==================================================================================
OSPFv3 Global Information - GlobalRouter
==================================================================================
router-id : 170.78.88.0
admin-state : ENABLED
version : 3
area-bdr-rtr-state : FALSE
as-bdr-rtr-state : FALSE
helper-mode : ENABLED
as-scope-lsa-count : 0
lsa-checksum : 0
originate-new-lsas : 22
rx-new-lsas : 11
ext-lsa-count : 0
Switch1:1(config)#show ipv6 ospf neighbor
==========================================================================================
OSPF Neighbor - GlobalRouter
==========================================================================================
IFINDX(VID/BRT/CLIP) NBRROUTERID NBRIPADDR STATE TTL
------------------------------------------------------------------------------------------
2050 (2) 170.78.84.0 fe80:0:0:0:b2ad:aaff:fe4e:5500 Full 31
1 out of 1 Total Num of Neighbor Entries displayed.
==========================================================================================
OSPF Virtual Neighbor - GlobalRouter
==========================================================================================
NBRAREAID NBRROUTERID VIRTINTFID NBRIPV6ADDR STATE
------------------------------------------------------------------------------------------
0 out of 0 Total Num of Virtual Neighbor Entries displayed.
==========================================================================================
OSPF NBMA Neighbor - GlobalRouter
==========================================================================================
INTERFACE NBRROUTERID NBRIPADDR STATE
------------------------------------------------------------------------------------------
0 out of 0 Total Num of NBMA Neighbor Entries displayed.
H = Helping a Restarting neighbor
Switch1:1(config-if)#exit
Configure RIPng on the VLAN.
Switch1:1(config)#interface vlan 2 Switch1:1(config-if)#ipv6 rip Switch1:1(config-if)#ipv6 rip enable
Switch1:1(config-if)#show ipv6 rip interface
Total RIPng interfaces: 1
================================================================================
RIPng Interface - GlobalRouter
================================================================================
IFINDX COST POISON SEND ADMIN OPER
STATUS DEFAULT STATUS STATUS
--------------------------------------------------------------------------------
2050 (2 ) 1 disable disable enable enable
1 out of 1 Total Num of RIPng interfaces displayed
Configure RIPng globally.
Switch1:1(config)#router rip ipv6-enable Switch1:1(config)#router rip
Switch1:1(config)#show ipv6 rip
==========================================================================
RIPng Global - GlobalRouter
===========================================================================
Rip : Enabled
HoldDown Time : 120
Timeout Interval : 180
Update Time : 30
Default Info Metric : 1
Default Info State : Disabled
Default Import Metric : 1
On Switch-2, configure VLAN 2 and VLAN 3 with the IPv6 interfaces 2000:0:0:0:0:0:0:2/64 and 3000:0:0:0:0:0:0:2/64 respectively.
Switch2:1>enable Switch2:1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch2:1(config)#vlan create 2 type port-mstprstp 0 Switch2:1(config)#vlan members 2 1/5 portmember Switch2:1(config)#interface vlan 2 Switch2:1(config-if)#ipv6 interface address 2000:0:0:0:0:0:0:2/64 Switch2:1(config-if)#ipv6 interface enable Switch2:1(config-if)#ipv6 forwarding Switch2:1(config-if)#exit
Switch2:1(config)#vlan create 3 type port-mstprstp 0 Switch2:1(config)#vlan members 3 1/6 portmember Switch2:1(config)#interface vlan 3 Switch2:1(config-if)#ipv6 interface address 3000:0:0:0:0:0:0:2/64 Switch2:1(config-if)#ipv6 interface enable Switch2:1(config-if)#ipv6 forwarding Switch2:1(config-if)#exit
Switch2:1(config)#show vlan basic
=======================================================================================
Vlan Basic
=======================================================================================
VLAN MSTP
ID NAME TYPE INST_ID PROTOCOLID SUBNETADDR SUBNETMASK VRFID ORIGIN
---------------------------------------------------------------------------------------
1 Default byPort 0 none N/A N/A 0 CONFIG
2 VLAN-2 byPort 0 none N/A N/A 0 CONFIG
3 VLAN-3 byPort 0 none N/A N/A 0 CONFIG
All 3 out of 3 Total Num of Vlans displayed
Switch2:1(config)#show vlan members
=======================================================================
Vlan Port
========================================================================
VLAN PORT ACTIVE STATIC NOT_ALLOW
ID MEMBER MEMBER MEMBER MEMBER
------------------------------------------------------------------------
1 1/1-1/4,1/7-1/24 1/1-1/16,1/7-1/24
2 1/5 1/5
3 1/6 1/6
All 3 out of 3 Total Num of Port Entries displayed
Switch2:1(config)#show ipv6 interface vlan
==================================================================================================================
Vlan Ipv6 Interface
==================================================================================================================
IFINDX VLAN PHYSICAL ADMIN OPER TYPE MTU HOP REACHABLE RETRANSMIT MCAST IPSEC RPC RPCMODE
INDX ADDRESS STATE STATE LMT TIME TIME STATUS
------------------------------------------------------------------------------------------------------------------
2050 2 b0:ad:aa:4e:55:00 enable up ETHER 1500 64 30000 1000 disable disable disable existonly
2051 3 b0:ad:aa:4e:55:01 enable up ETHER 1500 64 30000 1000 disable disable disable existonly
===================================================================================================================
Vlan Ipv6 Address
===================================================================================================================
IPV6 ADDRESS VLAN-ID TYPE ORIGIN STATUS NAME
-------------------------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:2/64 V-2 UNICAST MANUAL PREFERRED
fe80:0:0:0:b2ad:aaff:fe4e:5500/64 V-2 UNICAST LINKLAYER PREFERRED
3000:0:0:0:0:0:0:2/64 V-3 UNICAST MANUAL PREFERRED
fe80:0:0:0:b2ad:aaff:fe4e:5501/64 V-3 UNICAST LINKLAYER PREFERRED
2 out of 2 Total Num of Interface Entries displayed.
4 out of 4 Total Num of Address Entries displayed.
Configure ports 1/5 and 1/6.
Switch2:1(config)#interface GigabitEthernet 1/5 Switch2:1(config)#encapsulation dot1q Switch2:1(config)#no shutdown Switch2:1(config)#interface GigabitEthernet 1/6 Switch2:1(config)#encapsulation dot1q Switch2:1(config)#no shutdown
Configure IPv6 globally.
Switch1:1(config)#ipv6 forwarding
Switch1:1(config)#show ipv6 forwarding
Ipv6 forwarding - GlobalRouter : enable
ecmp : disable
ecmp-max-path : 1
Configure OSPFv3 on the VLANs.
Switch2:1(config)#interface vlan 2 Switch2:1(config-if)#ipv6 ospf area 0.0.0.0 Switch2:1(config-if)#ipv6 ospf enable Switch2:1(config)#interface vlan 3 Switch2:1(config-if)#ipv6 ospf area 0.0.0.0 Switch2:1(config-if)#ipv6 ospf enable
Switch2:1(config-if)#show ipv6 ospf
=================================================================================
OSPFv3 Global Information - GlobalRouter
=================================================================================
router-id : 170.78.84.0
admin-state : ENABLED
version : 3
area-bdr-rtr-state : FALSE
as-bdr-rtr-state : FALSE
helper-mode : ENABLED
as-scope-lsa-count : 0
lsa-checksum : 0
originate-new-lsas : 56
rx-new-lsas : 62
ext-lsa-count : 0
Switch2:1(config-if)#show ipv6 ospf interface
Total ospf areas: 1
Total ospf interfaces: 2
==================================================================================
OSPF Interface - GlobalRouter
==================================================================================
IFINDX(VID/BRT/CLIP) AREAID ADM IFSTATE METRIC PRI DR/BDR IFTYPE
----------------------------------------------------------------------------------
2050 (2 ) 0.0.0.0 ena BDR 1 1 170.78.88.0 BROADCAST
170.78.84.0
2051 (3 ) 0.0.0.0 ena DR 1 1 170.78.84.0 BROADCAST
0.0.0.0
2 out of 2 Total Num of ospf interfaces displayed
Total ospf virtual interfaces: 0
==================================================================================
OSPF Virtual Interface - GlobalRouter
==================================================================================
AREAID NBRIPADDR STATE
----------------------------------------------------------------------------------
0 out of 0 Total Num of ospf virtual interfaces displayed
Switch2:1(config-if)#show ipv6 ospf neighbor
==================================================================================
OSPF Neighbor - GlobalRouter
==================================================================================
IFINDX(VID/BRT/CLIP) NBRROUTERID NBRIPADDR STATE TTL
----------------------------------------------------------------------------------
2050 (2) 170.78.88.0 fe80:0:0:0:b2ad:aaff:fe4e:5900 Full 30
1 out of 1 Total Num of Neighbor Entries displayed.
===================================================================================
OSPF Virtual Neighbor - GlobalRouter
===================================================================================
NBRAREAID NBRROUTERID VIRTINTFID NBRIPV6ADDR STATE
-----------------------------------------------------------------------------------
0 out of 0 Total Num of Virtual Neighbor Entries displayed.
===================================================================================
OSPF NBMA Neighbor - GlobalRouter
===================================================================================
INTERFACE NBRROUTERID NBRIPADDR STATE
------------------------------------------------------------------------------------
0 out of 0 Total Num of NBMA Neighbor Entries displayed.
H = Helping a Restarting neighbor
Configure OSPFv3 globally.
Switch2:1(config-if)#exit
Switch2:1(config)#router ospf ipv6-enable
Switch1:1(config)#show ipv6 ospf
=====================================================================================
OSPFv3 Global Information - GlobalRouter
=====================================================================================
router-id : 170.78.88.0
admin-state : ENABLED
version : 3
area-bdr-rtr-state : FALSE
as-bdr-rtr-state : FALSE
helper-mode : ENABLED
as-scope-lsa-count : 0
lsa-checksum : 0
originate-new-lsas : 22
rx-new-lsas : 11
ext-lsa-count : 0
Configure RIPng on the VLANs.
Switch2:1(config)#interface vlan 2 Switch2:1(config-if)#ipv6 rip Switch2:1(config-if)#ipv6 rip enable Switch2:1(config-if)#exit Switch2:1(config)#interface vlan 3 Switch2:1(config-if)#ipv6 rip Switch2:1(config-if)#ipv6 rip enable Switch2:1(config-if)#exit Switch2:1(config)#
Switch2:1(config)#show ipv6 rip interface
Total RIPng interfaces: 2
========================================================================
RIPng Interface - GlobalRouter
========================================================================
IFINDX COST POISON SEND ADMIN OPER
STATUS DEFAULT STATUS STATUS
-------------------------------------------------------------------------
2050 (2 ) 1 disable disable enable enable
2051 (3 ) 1 disable disable enable enable
2 out of 2 Total Num of RIPng interfaces displayed
Configure RIPng globally.
Switch2:1(config)#router rip ipv6-enable
Switch2:1(config)#router rip
Switch2:1(config)#show ipv6 rip
=============================================================
RIPng Global - GlobalRouter
==============================================================
Rip : Enabled
HoldDown Time : 120
Timeout Interval : 180
Update Time : 30
Default Info Metric : 1
Default Info State : Disabled
Default Import Metric : 1
On Switch-1 and Switch-2, the route 3000:0:0:0:0:0:0:2/64 is learned using the protocols RIPng and OSPFv3. The OSPFv3 route is learned as the best route because of its route preference value of 20. The RIPng route is added as alternative route because it has the route preference 100, which is greater than the OSPFv3 route preference of 20. On Switch-2, the route 3000:0:0:0:0:0:0:2/64 is a local route.
View route and alternative route configuration on Switch-1.
Switch1:1(config)#show ipv6 route alternative
====================================================================================================
IPv6 Routing Table Information - GlobalRouter
====================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
----------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 B 20
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 RIP 2 0 A 100
----------------------------------------------------------------------------------------------------
3 out of 3 Total Num of Route Entries displayed.
----------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
Switch1:1(config)#show ipv6 route
===================================================================================================
IPv6 Routing Table Information - GlobalRouter
===================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
---------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 B 20
---------------------------------------------------------------------------------------------------
2 out of 2 Total Num of Route Entries displayed.
---------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
View route and alternative route configuration on Switch-2.
Switch2:1(config)#show ipv6 route alternative
======================================================================================================
IPv6 Routing Table Information - GlobalRouter
======================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
------------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:2/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 LOCAL 2 0 B 20
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 LOCAL 2 0 A 100
------------------------------------------------------------------------------------------------------
3 out of 3 Total Num of Route Entries displayed.
------------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
Switch2:1#show ipv6 route
==========================================================================================
IPv6 Routing Table Information - GlobalRouter
==========================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:2/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-3 LOCAL 1 0 B 20
------------------------------------------------------------------------------------------
2 out of 2 Total Num of Route Entries displayed.
------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
On the switch, default preferences are assigned to all standard routing protocols. You can modify the global preference for a protocol to give it a higher or lower priority than other protocols. When you change the preference for a static route, if all best routes remain best routes, only the local route tables change. However, if changing the protocol preference causes best routes to no longer be best routes, neighboring route tables can be affected.
In the following example scenario, you configure a different routing preference for the RIPng protocol on Switch-1 and observe the learning of best and alternative routes. The existing route preference for RIPng is 100.
Switch1:1#show ipv6 route alternative
========================================================================================================
IPv6 Routing Table Information - GlobalRouter
========================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
--------------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 B 20
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 RIP 2 0 A 100
--------------------------------------------------------------------------------------------------------
3 out of 3 Total Num of Route Entries displayed.
--------------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
Switch1:1(config)#show ipv6 route
===================================================================================================
IPv6 Routing Table Information - GlobalRouter
===================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
---------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 B 20
---------------------------------------------------------------------------------------------------
2 out of 2 Total Num of Route Entries displayed.
---------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
Configure a different route preference for the RIPng protocol, for example, 19.
Switch1:1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch1:1(config)#ipv6 route preference protocol ripng 19 Switch1:1(config)#exit
Verify the route preference configuration.
Switch1:1#show ipv6 route preference
========================================================================================
IPv6 Route Preference - GlobalRouter
========================================================================================
PROTOCOL DEFAULT CONFIG
----------------------------------------------------------------------------------------
LOCAL 0 0
STATIC 5 5
SPBM_L1 7 7
OSPFv3_INTRA 20 20
OSPFv3_INTER 25 25
EBGP 45 45
RIPNG 100 19
OSPFv3_E1 120 120
OSPFv3_E2 125 125
IBGP 175 175
View the updated route preference (for RIPng) on Switch-1. The RIPng route is now learned as the best route because its route preference value (19) is lower than that of OSPFv3 (20), as shown here.
Switch1:1(config)#show ipv6 route
===================================================================================================
IPv6 Routing Table Information - GlobalRouter
===================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
---------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 RIP 2 0 B 19
---------------------------------------------------------------------------------------------------
2 out of 2 Total Num of Route Entries displayed.
---------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
Switch1:1#show ipv6 route alternative
===========================================================================================================
IPv6 Routing Table Information - GlobalRouter
===========================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
-----------------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 RIP 2 0 B 19
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 A 20
-----------------------------------------------------------------------------------------------------------
3 out of 3 Total Num of Route Entries displayed.
-----------------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
The following example demonstrates disabling alternative route learning on Switch-1.
View the alternative routes on Switch-1.
Switch1:1(config)#show ipv6 route alternative
=======================================================================================================
IPv6 Routing Table Information - GlobalRouter
=======================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
-------------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 B 20
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 RIP 2 0 A 100
-------------------------------------------------------------------------------------------------------
3 out of 3 Total Num of Route Entries displayed.
-------------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
Disable IPv6 alternative routes on Switch-1.
Switch1:1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch1:1(config)#no ipv6 alternative-route Switch1:1(config)#exit
Verify that alternative route learning is disabled.
Switch1:1#show ipv6 global
forwarding : enable
default-hop-cnt : 64
number-of-interfaces : 1
icmp-error-interval : 1000
icmp-error-quota : 50
icmp-unreach-msg : disable
icmp-echo-multicast-request : enable
static-route-admin-status : enable
alternative-route : disable
ecmp : disable
ecmp-max-path : 1
source-route : disable
Switch1:1(config)#show ipv6 route
===================================================================================================
IPv6 Routing Table Information - GlobalRouter
===================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
---------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 B 20
---------------------------------------------------------------------------------------------------
2 out of 2 Total Num of Route Entries displayed.
---------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route
Verify that the alternative route (RIPng) is not learned.
Switch1:1(config)#show ipv6 route alternative
======================================================================================================
IPv6 Routing Table Information - GlobalRouter
======================================================================================================
Destination Address/PrefixLen NEXT HOP VID/BID/TID PROTO COST AGE TYPE PREF
------------------------------------------------------------------------------------------------------
2000:0:0:0:0:0:0:1/64 39-4900-24XE V-2 LOCAL 1 0 B 0
3000:0:0:0:0:0:0:2/64 SwitchXYZ V-2 OSPF 2 0 B 20
------------------------------------------------------------------------------------------------------
2 out of 2 Total Num of Route Entries displayed.
------------------------------------------------------------------------------------------------------
TYPE Legend:
A=Alternative Route, B=Best Route, E=Ecmp Route