problems while configuring Etherchannel?

[agurekian]

Hi,

I have a couple of 6500 and 3 couples of 4500.

Each couple of 4500 is connected to the 6500s this way (since I am not sure of the ASCII results: it should look like a SQUARE! 🙂 )

6500A ---- 6500B

| |

| |

4500A ---- 4500B

I have to double all the trunks, using Etherchannel (with the PAGP protocol).

Since this will be done in a production environment, I'd like to understand what this will imply.

1) is there a suggested order, or whichever trunk I upgrade first does not make any difference?

2) will the STP recalculations cause an interruption of service? And of which entity?

I could configure a diameter of 6 for the STP, but right now the switches are configured using the 'priority' keyword instead of the 'root primary' and 'root secondary' keywords.

Does the reconfiguration of this parameters start a new STP recalculation?

And how much will I 'gain' by configuring a diameter of 6 instead of the default? (which is the default? 7? 8?)

Any kind of info/help, even on a single question, will be greatly appreciated.

Thank you in advance.

Cheers

Aram

[aashish.c]

Hi Aram,

1. There is no order denied by cisco to transform the links in etherchannel. You can make links one by one. But for couple of seconds connectivity will be gone because of config mismatch one side and other while applying FEC and trunking commands on links.

2. when u put individual links in FEC, it act as 1 logical link and STP also treats that whole bundle of links as 1 link. all the values of STP, speed, duplex and allowed vlans on trunks should be exactly same on all the links of FEC otherwise FEC will not form.

3. on trunks when you will set priority for different vlans they will act normally in FEC as they do on normal trunks. But while changing priorities root bridges for vlans can change depending upon the values of priorities set for Vlans on switches.

4. Recommended STP diameter is 7. If u make 6 as ur diamter STP will run smoothly, there will not be any delay in BPDUs and calculations. But dont change delay timers and fwding time or BPDU circulation timers which is 2 sec. by default. Bcoz changing these timer vlaues may impact the network in unknown results depending on your network.

Kindly update if need any further clarification...

Thakns

aashish C