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lonelyadmin
Beginner

How to have a FT or HA link to 2 separate switches?

New to the 9200X line of switches. I'm trying to figure out the best way to uplink a single 9200X to two seperate 4500X switch stacks. Links don't have to be active/active load balancing (though that's preferred). If approach is active/standby I'd need to be able to at least do some simple logic (ping IP) to determine which link to use.

 

To be clear, I have two pairs of 4500X switches, each in their own VSS stack. Those two stacks connect to one another across a multichassis etherchannel trunk. I need to connect a 9200X to both 4500X switch stacks in a manner where a single 4500X stack failure (or reload) won't cause an outage.

 

If this isn't possible, would using a stacked pair of 9200X switches make a difference?

1 ACCEPTED SOLUTION

Accepted Solutions

Hello @lonelyadmin ,

if you build OSI L2 port channels you can simply rely on Spanning-Tree  ( a form of Rapid STP Rapid PVST or MST) and you can have VSS1 root bridge and VSS2 the backup root bridge so STP will keep in blocking alternate the port-channel to VSS2 and in forwarding state the port-channel to VSS1.

The 9200 catalyst needs to run the same flavor of STP.

 

if you have L3 routed port-channels you can use a routing protocol like OSPF and you can even achieve load balancing and redundancy anot not only fault tolerance like in the L2 case using STP.

 

Hope to help

Giuseppe

 

View solution in original post

4 REPLIES 4
Reza Sharifi
Hall of Fame Expert

So, the issue with this design is that if you connect a 9200 to different VSS sets, you can't use any Portchannels as the 9200 will see each VSS set as a different device and not one logical device/domain. The same problem also persists if you have a stack of 9200. I think the easiest way for this to work is to connect the 9200 (single or a stack of 2)  to one set of VSS since you already have redundancy between the VSS sets.

HTH 

That's pretty much what I've been doing in other places with similar setups. When there is an outage I usually have to either physically move cables if the link to the other stack doesn't exist or shut/no shut ports.

 

I understand that real multichassis portchannels likely will never happen on these class of switches. I'm wondering if I can go ahead and physically cable up to both stacks, each with their own portchannel and then manage the links from EEM or kron. I haven't done any work on the 9200X and don't know if there are any licensing hurdles...or even what capabiilities it has in that regard. But I think I'll look at finding a way to monitor the uplink to check for direct connectivity  (CDP on port-channel?)  and some remote check (icmp through the parent switch?) or what ever logic I can come up with and have the interfaces shut/no shut appropriately. Having an external monitor shell in or SNMP control it is possible as well.

 

Having a short outage while links change over is ok. Better than waiting on me to identify and verify the problem and then move cables or whatever.

Hello @lonelyadmin ,

if you build OSI L2 port channels you can simply rely on Spanning-Tree  ( a form of Rapid STP Rapid PVST or MST) and you can have VSS1 root bridge and VSS2 the backup root bridge so STP will keep in blocking alternate the port-channel to VSS2 and in forwarding state the port-channel to VSS1.

The 9200 catalyst needs to run the same flavor of STP.

 

if you have L3 routed port-channels you can use a routing protocol like OSPF and you can even achieve load balancing and redundancy anot not only fault tolerance like in the L2 case using STP.

 

Hope to help

Giuseppe

 

View solution in original post

lonelyadmin
Beginner

I like that idea...I sometime forget about those. I do have HSRP running on all of the L3 interfaces.