HSRP and Stack

[Danilo Dy]

Hi,

I'm thinking about some usage of HSRP compare to Stack. Need advice to verify if I'm correct.

I currently have two L3 (non-stackable switch) configure HSRP in SVI for my clustered firewall gateway (each firewall is physically connected to each switch). The switch is connected to each other with a trunk. This setup is to provide physical L3 switch redundancy.

Now, if I have two L3 (stackable switch) and I stack them together, configure SVI as my clustered firewall gateway (each firewall is physically connected to each switch). This setup also provide physical L3 switch redundancy, since any of the switch fails the SVI that is a gateway for clustered firewall is still up.

Thus the above assumption is correct?

Also what is the longest stack cable for 3750 switch? What is the part number?

[Anand Narayana]

Hi Medan,

maximum of 9 stack switches can be connected on an 3750, stacking cable length is not more than 3 mtr.

[royalblues]

As anand said earlier, you can stack upto 9 switches together.

This setup also provides redundancy as you can build etherchannels across different chassis within a stack. (only HSRP though, it does not support VRRP)

The only problem would be when the stack fails you will two different stack master with the same IP which can create ip conflicts within the partitioned domain.

The part number for the stacking cable would be CAB-STACK-3M (for a 3M cable)

By default cisco ships a 50CM stack cable

part number CAB-STACK-50CM

HTH, rate if it does

Narayan

[Danilo Dy]

Hi All,

Thanks for your reply. The question regarding cable length has been answered.

I know about the 9 switch in the stack.

My question about replacing HSRP's physical L3 switch redundancy be replaced with stack switch which I also considered physical redundancy if I configure the gateway in SVI. This is because of the number of HSRP group that can be created in a switch (32 for 3750), I'm looking for a solution to get rid of HSRP but still able to meet physical L3 switch redundancy by connecting clustered firewall in each switch. I think I have to post a diagram tomorrow of what I'm trying to say :)

[royalblues]

Medan,

Stacking does remove the dependency on HSRP but still providing redundancy..

Post the network diagram to know exactly what needs to be achieved

Narayan

[Anand Narayana]

yeah it would be better that if you could post the diagram so that i can come to know what exactly you want achieve.

[Danilo Dy]

Hi All,

For continuing the HSRP/STACK discussion, see attached diagram. In the left is HSRP diagram, we know that in HSRP if the active switch fails, the standby switch becomes active. This is gateway redundancy and physical switch redundancy. Take a look on the right diagram, since gateway is configured in SVI, that SVI will still be up even if the master switch fails, as the other switch will become master. So it also provides gateway redundancy and physical switch redundancy.

Thus that mean any of the solution works for clustered (active/active) firewall below the diagram?

BTW, I just found out that though the 3750 HSRP group limit is 32, we can reuse it for 1000 SVI, theoritically we can create 32000 HSRP in SVI. Check the discussion in ASK THE EXPERT- NEW CATALYST 3750-E AND 3560-E SWITCHES http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=LAN%2C%20Switching%20and%20Routing&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1dde1bfa

[Anand Narayana]

Hi Medan,

ur right that you get redundancy in HSRP as well as in Stack, but one thing you should consider, when you say HSRP the switches can be located in any location, i mean Main Switch in 1st floor & standby switch in 10th floor, but when you say Stack switch, all the switches should be placed with 3Metrez only, bcoz maximum cable length in stack switches will not exceed more than 3Metrez.

hope you agree this. rate this post if satisfied.

[Anand Narayana]

Hi Medan,

ur right that you get redundancy in HSRP as well as in Stack, but one thing you should consider, when you say HSRP the switches can be located in any location, i mean Main Switch in 1st floor & standby switch in 10th floor, but when you say Stack switch, all the switches should be placed with 3Metrez only, bcoz maximum cable length in stack switches will not exceed more than 3Metrez.

hope you agree this. rate this post if satisfied.

[Danilo Dy]

Thanks for the confirmation :)

I may not use the STACK anyway after knowing that I can create up to 32000 HSRP in SVI :). But it's good knowledge that there is an alternative.