HSRP with Interface VLANs

　　Introduction

　　In this configuration, we have two Catalyst 6509 switches, each with two Multilayer Switch Feature Cards (MSFCs), for a total of four routers. Our strategy is to have the MSFC-a1 in the diagram below route for odd virtual LANs (VLANs), as the primary router, and MSFC-b1 to route odd VLANs as the backup router. For even VLANs, we want MSFC-b2 to be the primary router and MSFC-a2 to be the backup router.

　　Note: The backup routers (MSFCs) don't have a standby priority explicitly assigned so they default to priority 100. We add the standby preempt statement so that if the primary router goes down and comes back up, it resumes the highest priority, or preempt control.

　　MSFC-a1配置信息：

　　msfc-a1#

　　!

　　hostname msfc-a1

　　!

　　!

　　interface Vlan1

　　ip address 1.1.1.2 255.255.0.0

　　standby 1 priority 110 preempt

　　standby 1 ip 1.1.1.1

　　!

　　interface Vlan3

　　ip address 3.1.1.2 255.255.0.0

　　standby 3 priority 110 preempt

　　standby 3 ip 3.1.1.1

　　!

　　!

　　end

　　MSFC-a2配置信息：

　　msfc-a2#

　　!

　　hostname msfc-a2

　　!

　　!

　　interface Vlan2

　　ip address 2.1.1.3 255.255.0.0

　　standby 2 ip 2.1.1.1

　　!

　　interface Vlan4

　　ip address 4.1.1.3 255.255.0.0

　　standby 4 ip 4.1.1.1

　　!

　　!

　　end

　　MSFC-b1配置信息：

　　msfc-b1#

　　!

　　hostname msfc-b1

　　!

　　!

　　interface Vlan1

　　ip address 1.1.1.3 255.255.0.0

　　standby 1 ip 1.1.1.1

　　!

　　interface Vlan3

　　ip address 3.1.1.3 255.255.0.0

　　standby 3 ip 3.1.1.1

　　!

　　!

　　end

　　MSFC-b2配置信息：

　　msfc-b2#

　　!

　　hostname msfc-b2

　　!

　　!

　　interface Vlan2

　　ip address 2.1.1.2 255.255.0.0

　　standby 2 priority 110 preempt

　　standby 2 ip 2.1.1.1

　　!

　　interface Vlan4

　　ip address 4.1.1.2 255.255.0.0

　　standby 4 priority 110 preempt

　　standby 4 ip 4.1.1.1

　　!

　　!

　　!

　　end

　　相关命令与讲解如下：

　　debug and show Commands

　　Verify that HSRP is working by using the show standby command. In the output below, MSFC-a1 sees its backup router as "Standby router 3.1.1.3."

　　msfc-a1#show standby

　　Vlan1 - Group 1

　　Local state is Active, priority 110, may preempt

　　Hellotime 3 holdtime 10

　　Next hello sent in 00:00:01.588

　　Hot standby IP address is 1.1.1.1 configured

　　Active router is local

　　Standby router is 1.1.1.3 expires in 00:00:08

　　Standby virtual mac address is 0000.0c07.ac01

　　Vlan3 - Group 3

　　Local state is Active, priority 110, may preempt

　　Hellotime 3 holdtime 10

　　Next hello sent in 00:00:02.092

　　Hot standby IP address is 3.1.1.1 configured

　　Active router is local

　　Standby router is 3.1.1.3 expires in 00:00:08

　　Standby virtual mac address is 0000.0c07.ac03

　　When we issue the show standby command from MSFC-b1, we see that for VLAN 1 and 3, MSFC-b1 is the backup or standby router: "Local state is Standby, priority 100." The active router is 1.1.1.2, or MSFC-a1, which has priority 110. Since 110 is greater than 100, MSFC-a1 is the active router.

　　msfc-b1#show standby

　　Vlan1 - Group 1

　　Local state is Standby, priority 100

　　Hellotime 3 holdtime 10

　　Next hello sent in 00:00:01.440

　　Hot standby IP address is 1.1.1.1 configured

　　Active router is 1.1.1.2 expires in 00:00:09

　　Standby router is local

　　Standby virtual mac address is 0000.0c07.ac01

　　Vlan3 - Group 3

　　Local state is Standby, priority 100

　　Hellotime 3 holdtime 10

　　Next hello sent in 00:00:01.478

　　Hot standby IP address is 3.1.1.1 configured

　　Active router is 3.1.1.2 expires in 00:00:09

　　Standby router is local

　　Standby virtual mac address is 0000.0c07.ac03

　　When HSRP isn't configured correctly, you see show standby output similar to that below, which shows MSFC-b2 doesn't see its HSRP partner.

　　msfc-b2#show standby

　　Vlan2 - Group 2

　　Local state is Active, priority 110, may preempt

　　Hellotime 3 holdtime 10

　　Next hello sent in 00:00:02.904

　　Hot standby IP address is 2.1.1.1 configured

　　Active router is local

　　Standby router is unknown expired

　　When you see this output, first check that the configuration is correct. Then verify that all the VLANs are passing through the trunk between the two switches. In the output below, VLANs 1 through 4 are passing through correctly.

　　Switch (enable)#show trunk 8/1

　　Port Mode Encapsulation Status Native vlan

　　-------- ----------- ------------- ------------ -----------

　　8/1 desirable n-isl trunking 1

　　Port Vlans allowed on trunk

　　----------------------------------------------------------------

　　8/1 1-1005

　　Port Vlans allowed and active in management domain

　　----------------------------------------------------------------

　　8/1 1-4

　　Port Vlans in spanning tree forwarding state and not pruned

　　----------------------------------------------------------------

　　8/1 1-4

　　If you're still running into issues, ensure that the virtual VLAN interfaces are up by issuing the show interface vlan command.

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