How to configure router to connect to two different stack switch belonging to the same broadcast domain?

[rrairineo1]

Hi all,

I have this design plan for redundancy for our stack switch. i have simulated it and works perfectly fine (using STP). Somehow I notice i cannot simulate the router to switch connection. The routers will be connected to the two stack switches but they all belong to the same broadcast domain. I believe for every interface of the router means a broadcast domain. I want to connect two interfaces of the router to each of the stack switch belonging to the same broadcast domain. how can i do it? or if not, are there any suggestions. For now, i am limited to do changes on the IP allocation that's why i thought of this. please see attached diagram for reference.

thanks and best regards, 

[Mark Malone]

Hi yes correct there layer 2 ports in hwic and you can use stp cost to chose which link will be active , that's all the hwic does really gives a router layer 2 capabilities

[rrairineo1]

thank you very much for your help. i think my problem is solved. until next time. thanks for your expert advice.  

[Mark Malone]

No problem if you get stuck during setup just respond back to this thread it will still email me anyway save you opening another post and going through everything again

[rrairineo1]

hi. changed plans. i was advice that i can now use vss instead of the 3750 stack switches. (same scenario as the one i presented here). i would like to ask which is better to use 6500, 4500, or 6800? i am really new at this one. never used any of those (or the vss setup). My consideration for this one is just ease of maintenance and troubleshooting aside from HA. Moreover,i will  still be needing the hwic module right? (dont have enough ports on the router) if that's the case then can i use the same stp concept? or what better setup do you recommend? thank  you.  

[Mark Malone]

Hey If your using VSS use a port-channel from each access level switch, a link to each of the VSS switches ,loadbalance your user traffic across both switches at same time for redundancy and best throughput and unfortunately I don't think HWICs support bonding so you will still have 1 active 1 blocked stp link to your routers if you require 2 links or you can go full routed is the other choice as mentioned before all p2p link advertised on VSS between routers and then use eigrp to load balance out the links to the routers keeping the all active , but then you will need a capable license on VSS which could be expensive

use these commands on vss and user switches, you can change the type of LB but this one works well usually

platform ip cef load-sharing ip-only
port-channel load-balance src-dst-port

[rrairineo1]

hi thank you. for the access level switch that is noted ill use port-channel to connect it to each member of vss switches. what would you recommend to use: 4500, 6500, or 6800? for the connection from router to vss switches i think ill follow this one. (please refer to the attached file). my only problem is that what module should i use to the router? can i use portchannel for this also? (router connecting to each members of the vss) logically the router sees the vss as one right?(please refer to the second file attached). please comment if you see design conflict. thanks.

PS

i think i can use the list attached for the modules. better preference for the module?

[Mark Malone]

4500 is obviously cheapest 65s and 68s are big switches lot power , it depends on how many users you have etc and what type of bandwidth they require but if you thought a stack would do a pair of 45s definitely would , you need specific modules and sups for VSS switches , in 65s they are all 67xx and sups start with VS, I think it could be same on 4500

hwics dont support port-channels unfortunately so only 1 link will be active per router STP will block the other to prevent a loop , yes the router and all devices see the VSS as 1 switch only , even when you log in it looks like 1 switch but you can jump between them with certain commands

2 good docs I keep handy as I have a few vss setups , some good pointers in them

http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-virtual-switching-system-1440/prod_qas0900aecd806ed74b.html

https://supportforums.cisco.com/document/124626/virtual-switching-system-vss-configuration-cisco-4500-series-switches

[rrairineo1]

"In Cisco IOS Release 12.4(17.6), EtherChannel support is introduced for embedded Fast Ethernet and Gigabit Ethernet interfaces on Cisco 2811, Cisco 2821, Cisco 2851, Cisco 3825 and Cisco 3845. Additionally, the same feature is also supported on the NM-1GE, HWIC-1GE-SFP, HWIC-1FE and HWIC-2FE modules in the earlier IOS release."

http://www.cisco.com/c/dam/en/us/products/collateral/routers/3800-series-integrated-services-routers-isr/prod_white_paper0900aecd806f698a.pdf

- does this mean if i use one of the modules stated, then i can now use port-channel (from router to vss)?

[Mark Malone]

Yes looks like it , last time I checked those hwics couldn't use etherchannels , that's good to know but you would want at least a 2port gigabit card

[rrairineo1]

thank you for your suggestion. thank you for sharing good pointers. i will be reading the references. until next time.