Cluster/SMLT and Stack/DMLT questions?

[Apollo77]

Hello,
In attachment are the schemes of the current network state and our proposal for implementing redundant links with Cluster+SMLT technology.
We want to create a redundant links (max 20)and get short failover time and the ability to keep the current versions of software (we are satisfied with current).
Nortel Switch 5510 is on base software version 4.0 and the other one is just a reserve. It works as Layer 3 with static routes.It has default route. With these two switches we want to create cluster and SMLT links to other network devices. I need answers for the following questions:

1. When we create a cluster with two switches, do we need to buy Advance Routing License for both switches?
2. Do we have to specifically configure SMLT links to other network devices (Nortel stack, Cisco 2960, 1841, Nortel 2526, ..there is few MLT links from Nortel 4524) or on the cluster concept it is unnecessary?
3. Is it necessary to upgrade software version on the Nortel 5510 switches?
4. Does the 4.0 version software has a demo license for advance routing such as for 5.1 and 6.1 versions?
5. If we want to suggest Stack + D/MLT Technology(5510 in the stack) instead of Cluster + SMLT what would be lost by the failure of one of th 5510 switches-power or cable failure? Note that 5510 is currently working as L3 and with a default route configured. Is it Cluster+SMLT for the L3 level, and Stack + D/MLT only for L2 considering default gateway on the switch?
6. What are the advantages of Cluster + SMLT compared to the Stack + D/MLT for which we don’t need advance license?

Thanks in advance...

 

[andy88]

1,3. To configure SMLT on the 5510 switches you will need version 5 or above software. You will also need to purchase advanced routing license to enable SMLT.

2. You can use MLT as well as SMLT at the same time on the 5510. It would be worth running everything as SMLT as it would require no config changes on the edge switches but gives more resiliency.

4. Version 4 doesn't require a licence.

5,6. SMLT is a L2 feature not L3. If you went with SMLT you would have to configure VRRP for L3 functions.

With your network i'm not sure there would be much difference if a switch failed with either setup. As with SMLT and DMLT once a link/switch goes down traffic will instantly traverse the remaining links.

 

[Apollo77]

I suppose I need advance licenses for both 5510 switches?
Upgrading the switches I can try demo licenses for Cluster/SMLT.
If I try with stack/DMLT scenario do I have to make some config changes on other devices?
My only concern is when one of the switches in stack goes down will another one continue to work as normal with remaining links after a period of time. Concern is also for configured default route on switch (or in this scenario - stack).
Anyhow thanks for answers.

 

[andy88]

Yes, you need a license for both switches if running SMLT.

If you can get a demo licence, then you will be able to test SMLT.

With DMLT you shouldn't need to change any config on the remote switches.

If a switch fails in a stack, then there should be no real loss of traffic as DMLT will continue to work on the remaining switch.

As long as the next hop router is connected via DMLT then a switch failure won't affect routing. If you only have a single connection to the router then if the switch it's connected to fails then you will lose routing.

 

[DutchBaZ]

If the switches are in the same room, i would advice to stack them and configure a DMLT. The 5510 series are not the best when using SMLT. Especially using older SW versions like 4.x!

Also a small note on the cisco config. I would configure the etherchannel with 'mode on' only as on other modes the EC can be instable.

Cheers
Bas