we are in the planning phase for a network upgrade. We have two C2960 Switches connected via one (L2) Etherchannel (4x1 Gbit/s) which works very well. In the next phase we would like to upgrade our router to an 2911 series which has 3 gb interfaces. and indeed we would like to create an etherchannel as well. our plan is to use 2 of the 2911 to connect to the first 2960 switch and the one left to the other 2960. i think we will achieve some redundancy with this config.
has anyone build some config like that or is it nosense? setting up one etherchannel wouldn´t work i think?! what is the best way for this?
so we really appreciate our input :-)
Talk about "redundancy". If your router fails, then you have ....
Besides, you want to tell me that you've got something that can push 1 Gbps when your router can't?
so i´d like to descripe my "redundancy" goals ;-)
As you can see, we have one router and two switches, as well. I am not talking about HSRP or something similar, we would like to achive a "redundancy" for the network in case that on switch fails (example : hardware failure of Switch A or B or a cable disconnect (human or material)).
I would like to explain in detail.
In a normal network you connect your router with one port to your Switch A and this one is connected to another Switch called Switch B. So your PC is connected to Switch B, and somehow the cable from router to Switch A failed. So what happens? No Internet, and maybe no interVLAN Routing (in case of L2 Switches). You couldn´t reach your servers etc.
My Idea, connected one Port to Switch A and one (maybe two) to Switch B. In case that one Switch fails, the other could reach the internet and servers.
i hope i could explain it quiet a little bit.
what about backups between seperate vlans? the switches are all l2 ...
i appreciate your service
Leo was talking about single point of failure. That means that as per Leo's scenarion the router fails (the hardware) you can't back up anything. You would need to have at least another 2911 to plan/design a minimum of redundancy.
Assuming you have only one broadcast domain (vlan) then the uplinks to the router will create a loop but STP (if you use it) will set one of the uplinks to BLOCKED. So you will NOT have the opportunity to use both of uplinks(loadbalancing) but you will have uplink redundancy.
Be carefull about the router (single point of failure) if you run critical traffic though it because if it fails then you need to think of an high availability scenario (Active-Active, Active-Standby)
Are you using an etherswitch module on your 2911 router? If not, you cannot create a Layer 2 etherchannel to connect to the 2960 switches - you should be able to utilize a Layer 3 etherchannel, however. Also, without an etherswitch module you will be unable to create multiple interfaces on the router that belong to the same subnet, thus preventing the type of redundancy you are looking for.
If I am correct assuming you don't have an etherswitch module, your best bet is to utilize a BVI (Bridge Virtual Interface) which will function similar to a Layer 3 SVI. Please see the Cisco document regarding BVI's.