Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

redundant LAN using FEC and spanning tree

I would like to setup a LAN switching environemnt that is totally redundant by using spanning tree and FEC technology. The idea is to have 4 NICS in each server and two stacked 3750 switched. I will use FEC to create a 4 NIC team with 2 NICS connected to switch A and two NICs connected to switch B. I am counting on spanning tree to recognize the redundant paths to the virtual MAC address of the team in order to achieve switch redundancy and FEC will take care of failure at the NIC and/or port level. Will this work? Comments?

Thanks,

Diego

1 ACCEPTED SOLUTION

Accepted Solutions
Purple

Re: redundant LAN using FEC and spanning tree

I think what you are asking about is if you can do cross stack etherchannel on the 3750 and the answer is yes . Just setup the etherchannel like you normally would , if switch in the stack fails it should continue to run on the other 2 channels in the stack . In saying this you also have to think about uplink reduncancy , if your uplink is on a switch that dies then you are out of the water anyway so at the very least you will need 2 uplinks in the stack for redundancy . You take a look at this link for the 3750 etherchannel info. Read the info about doing crossstack etherchannel .Also make sure when stack the 3750's you use 2 stack cables not just 1 . .http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_guide_chapter09186a00801cdea1.html

8 REPLIES

Re: redundant LAN using FEC and spanning tree

The servers will not talk BPDU, so I am not sure what you meant by they will run STP. The switch will run STP, blocking the redundant link that will create a loop. The FEC that you will use to connect to the server will have to be access FEC not trunk, I doubt the server will talk dot1q. The channel or FEC is a logical bundle of all the ports in the FEC therefore they will all be in forwarding mode. The STP to the servers will not give you redundancy but the FEC in itself will give you the redundancy where is one link is to fail you still have the other link or the other 3 links to carry the traffic.

New Member

Re: redundant LAN using FEC and spanning tree

Wow, thanks for blowing my idea full of holes! ;) Anyway, I don't expect the server(s) to do any STP or BDPU. I was hoping that the servers would have one virtual NIC with one IP and all of this would be transparent to the servers because of FEC. The switches using STP/BPDU would take care of the rest. I guess I oversimplified things. Do you have any ideas how I can accomplish this?

TIA,

Diego

Re: redundant LAN using FEC and spanning tree

Then there is nothing else to do with the switch but enable port channeling to the server's NICs that supports channeling.

New Member

Re: redundant LAN using FEC and spanning tree

I guess I didn't make myself clear in my original post. I have used FEC with multiple NICs in my servers for years and I think its great. NIC goes bad, you're covered. Port goes out, you're covered. And if all is good you have 2x or 4x the bandwidth of a single NIC!! But what happens if an entire switch goes out? I don't want to have to unplug a bunch of cables and plug into warm standby switch. I would like my servers to be connected to two switches at the same time so if an entire switch goes out I am also covered. I also want to keep using the added bandwidth and single IP simplicity of FEC. I'm I asking for too much? Is this possible somehow?

TIA,

Diego

Blue

Re: redundant LAN using FEC and spanning tree

You can't split the FEC between 2 switches. Your scenario might work, but load balancing towards the server would be unpredictable. The server would also see his own broadcasts -- not sure if that would be a problem or not. The switches would constantly see the virtual mac coming from a different port, which would generate a lot mac address flapping errors.

A better approach would be fault tolerant teaming on the server with NICs connected to 2 switches. One NIC will be active and the other standby. You might need to upgrade to gig NICs for bandwidth, but overall it would be a cleaner solution.

Please rate helpful posts.

Purple

Re: redundant LAN using FEC and spanning tree

I think what you are asking about is if you can do cross stack etherchannel on the 3750 and the answer is yes . Just setup the etherchannel like you normally would , if switch in the stack fails it should continue to run on the other 2 channels in the stack . In saying this you also have to think about uplink reduncancy , if your uplink is on a switch that dies then you are out of the water anyway so at the very least you will need 2 uplinks in the stack for redundancy . You take a look at this link for the 3750 etherchannel info. Read the info about doing crossstack etherchannel .Also make sure when stack the 3750's you use 2 stack cables not just 1 . .http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_guide_chapter09186a00801cdea1.html

Blue

Re: redundant LAN using FEC and spanning tree

Glen is right on. If both switches are the same 3750 stack the FEC will work fine. I thought you meant separate stacks, but I misread the original post.

New Member

Re: redundant LAN using FEC and spanning tree

Looks like I will read up on the doc that Glen suggested and go with the 3750 stack with one etherchannel port on each switch.

Thanks guys!

Diego

137
Views
0
Helpful
8
Replies