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3750 Stacking and HSRP...

Jason Whitehead
Level 1
Level 1

Before I had two 3750 Switches without stacking, I had HSRP setup per interface on the two switches.

If the master switch fails the other member in the standby group would take over:

switch#1

      interface GigabitEthernet0/1

      no switchport

      ip address 10.10.10.2 255.255.255.0

      standby 1 ip 10.10.10.1

      standby 1 timers 3 5

      standby 1 priority 110

      standby 1 preempt

switch#2

     interface GigabitEthernet0/1

     no switchport

     ip address 10.10.10.3 255.255.255.0

     standby 1 ip 10.10.10.1

     standby 1 preempt

I then stacked the switches and from my understanding when you stack the switches they become one logical unit with one management interface. I cannot have 2 interfaces configured to the same subnet if they are acting as one unit ( Overlaps ). I would lose the capability to do HSRP.

I would imagine i would need to make a VLAN and assign the the vlan interface with one ip address, in this case it would be 10.10.10.1 255.255.255.0

and add the port on each switch as a member of that VLAN.

Should I then put the two ports in a Etherchannel? that would rid of STP on the redundant link.

Let me know if I am correct on this or any advice appreciated.

1 Accepted Solution

Accepted Solutions

Hello Jason,

If your access-layer switch supports LACP then I would recommend to bundle with it, following would be cfg sample :

StackedSwitch(config)#

stack-mac persistent timer 0

interface port-channel 1

no switchport

ip address 10.10.10.1 255.255.255.0

interface GigabitEthernet 1/0/1

no switchport

no ip address

channel-protocol lacp

channel-group 1 mode active

interface GigabitEthernet 2/0/1

no switchport

no ip address

channel-protocol lacp

channel-group 1 mode active

thanks,

rahul.

View solution in original post

8 Replies 8

Karel Vins
Level 1
Level 1

Hi,

you are right. You have to assign IP to VLAN interface (SVI) and these two port add to this VLAN.

You can do "multi-chasis" etherchannel as you mention.

Regards,

Karel V.

Edison Ortiz
Hall of Fame
Hall of Fame

Not clear on your previous setup. It seems you had a point-to-point connection between these switches, unless these switches were connecting to a layer2 switch and providing HSRP services for that Vlan.

If you want to duplicate the setup with a stack, you can either go with SVI + L2 Etherchannel or simply go with L3 Etherchannel. Now, I'm implying this switch is connecting to a Layer2 switch that is servicing such Vlan.

Rahul Kachalia
Cisco Employee
Cisco Employee

Hello Jason,

That is correct. Network is greatly simplified and hardware-driven fault detection/recovery with logical switching system. StackWise simplifies control and management of one large system and with distributed/cross-stack network paths you can bundle into single logical p2p EtherChannel interface to simplify network topology.

Based on configuration you provided, you may keep this ports in Layer 3 mode add use Layer 3 Port-Channel:

- Add new Layer 3 Port-Channel on StackWise switches.

- Configure HSRP VIP as IP address on this interface.

- Bundle interfaces from SW1 and SW2 in same EtherChannel.

- Remember to configure "stack-mac persistent timer 0"

- Finally you may take off HSRP configuration.

For additional detail, refer to Chapter 2 - Deploying Cisco Catalyst 3750-X StackWise Plus section from following url:

http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/Borderless_Campus_Network_1.0/Borderless_Campus_1.0_Design_Guide.pdf

thanks,

rahul.

Joseph W. Doherty
Hall of Fame
Hall of Fame

Disclaimer

The Author of this posting  offers the information contained within this posting without   consideration and with the reader's understanding that there's no      implied or expressed suitability or fitness for any purpose.    Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind.  Usage of   this posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

Once you stack the switches, they indeed become one logical switch.  The solutions for putting an IP on two ports (same logical switch) are: place the ports into a VLAN and put the IP address on VLAN (also works with HSRP, which you might want to retain to avoid MAC change if stack master fails) or, I think(?), creating a L3 port channel.

Oh, although you may no longer need STP by design, offen good idea to keep it active in case someone inadvertly loops your switches.

Jason Whitehead
Level 1
Level 1

Hello all,

Thank you for your quick replies, I have made the following configuration changes and everything seems to

be operational. did I miss anything?

StackedSwitch(config)#

stack-mac persistent timer 0

interface port-channel 1

no switchport

ip address 10.10.10.1 255.255.255.0

interface GigabitEthernet 1/0/1

no switchport

no ip address

channel-group 1 mode on

interface GigabitEthernet 2/0/1

no switchport

no ip address

channel-group 1 mode on

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind.  Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Looks reasonable.

I see you also found the command to keep stack's mac across stack master change.  Using HSRP still offers two slight advantages.  First, it stays the same even across a reboot, recall(?) persistent mac doesn't; second it makes it easy to migrate gateway to another platform if the need ever arises.

Hello Jason,

If your access-layer switch supports LACP then I would recommend to bundle with it, following would be cfg sample :

StackedSwitch(config)#

stack-mac persistent timer 0

interface port-channel 1

no switchport

ip address 10.10.10.1 255.255.255.0

interface GigabitEthernet 1/0/1

no switchport

no ip address

channel-protocol lacp

channel-group 1 mode active

interface GigabitEthernet 2/0/1

no switchport

no ip address

channel-protocol lacp

channel-group 1 mode active

thanks,

rahul.

Thank you for the help!

I made a LAG between the Cisco stack to a dell switch using LACP, everything is working great!

Thanks everyone

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