How best to stack 3 x SGE2010

muppetgeoff · ‎07-22-2010

Hi,

I hope I posted this in the right place! Apologies if not, I will happily remove and repost in the right place. But I hope someone can help.

I have 2 x SGE2010 switches, currently running 2 seperate networks, and a new one just arrived. The two networks have reached thier capacity, and both need the expansion that this new one would provide.

Currently, we have our servers multi-homed, such that (for example) ServerA has 2 interfaces, each 1Gbit, and each interface plugged into switch.

Now before someone suggests buying a Backplane/Blade style switch - I have no choice. This is the kit I have to work with. So I need to make it work as best I can

So I have a couple of questions, which I can't seem to find answer to:

In stacking mode, the ports used for the stack - are they used for transferring configuration info only? or do they server as the bandwidth for the inter-switch traffic?
If I change the server configuration, creating a 2-port bonded link (so 2Gbit) and then connect one link into switch A, and 1 into switch B, can I create a LAG group that has members on different physical switches (but the same Vlan)?
How would YOU interconnect the switches? Stack them? or just use LAG groups for the interconnects?

I could (if the interconnecting bandwidth is sufficient) reconfigure the 2 LANs into one, bridging the 3 switches. Or continue with the split, and just VLan the new one. Again, bandwidth is a BIG issue - all our users are either Audio engineers, or Graphics designers. That is why we went down the seperate LAN/Link route.

Just to confuse things a bit more, we have a further 3 SRW2048 switches. I know these are not 'stackable', so I will just use LAG groups like we currently are.

Kind regards,

Geoff

Jayakrishna Mada · ‎08-03-2010

Hi Geoff,

See answers inline, I havent worked with specifically with SGE2010 switches but this should be same as the 3750 stackable switches.

In stacking mode, the ports used for the stack - are they used for transferring configuration info only? or do they server as the bandwidth for the inter-switch traffic?

[Jaya] The stack ports are used to transfer data between the switches as well.

2. If I change the server configuration, creating a 2-port bonded link (so 2Gbit) and then connect one link into switch A, and 1 into switch B, can I

create a LAG group that has members on different physical switches (but the same Vlan)?

[Jaya] Yes assuming that the server supports LAG, you can configure LAG on switch as well.

3. How would YOU interconnect the switches? Stack them? or just use LAG groups for the interconnects?

[Jaya] It all depends on how you want to look at the switches. All 3 as one switch or adminstor all 3 seperately. Personally I would stack them and

the resaons are:

1. STP will block one of the redundant port or LAG link if you have redundacny between these 3 switches.

2. Though you use LAG its not 100% load-balanced between the links it depends on the etherchannel alogrithm.

3. You need to have ip's assigned to each switch seperately.

http://www.cisco.com/en/US/docs/switches/lan/csbms/sfe2000/administration/guide/SFE-SGE2xxx_Admin_Guide.pdf

Hope this helps.

JayaKrishna

muppetgeoff · ‎08-05-2010

Thanks for the reply JayaKrishna.

If I stack them, how would I go about increasing the link speed between them? 1Gbps isn't fast enough.

Kind regards,

Geoff

Jayakrishna Mada · ‎08-05-2010

Hi Geoff,

I read the docs on SGE2010 unlike 3750 they dont have seperate stack ports. As you might already know we use port 12 and 24 or GBIC ports for stacking.

So the stack speed is 1gig vs 32gig on 3750.

With that said if your concern is bandwidth of stack ports then you might want to connect these 3 switches using port channel and load-balance the valns across them if you going to connect them in a triangle topology.

How are you going to connect these switches ?

switch 1---switch 2---switch3--network ? (no redundacny but no blocking ports)

or

switch1 (redundancy and also blocking ports unless you load-balance vlans)

/ \

switch 2 -----------switch 3

muppetgeoff · ‎08-10-2010

Hi,

I think I have settled on the following:

Switch 1 = Network 1

Switch 2 = Shared Network 1 and 2 (2 Vlans - ID 1 'Default', ID 2 'Network 2'))

Switch 3 = Network 2

4 ports on Switch 1 to Switch 2 (Network 1 Vlan) in LAG group, Trunk mode.

4 Ports on Switch 3 to Switch 2 (Network 2 Vlan) in LAG group, Trunk mode.

In this configuration, they are not 'stacked' (i.e. no central management) and I am aware that if I introduce the 'Stack' ports, I will merge the 'Default' Vlan (i.e. Vlan ID number 1) which - at the moment - is the Vlan ID of switch 1 and switch 2.

If I want to introduce stacking, I would need to move all the ports on Switch 3 to the Vlan ID 2 'Network 2' Vlan BEFORE stacking. Is that right? Otherwise the stack will merge those two switches.

Also, if I am using a LAG group in Trunk mode to facilitate the bandwidth to the 'Default' VLAN group, will this interfere with the stack ports?

I have noticed that I can only access the WebUI of the switch, if I am plugged into a port that is a member of the Default Vlan, irrespective of my IP address. I understand why (Vlan is a logical equivalent to seperate physical switches) but if I move all the ports into thier respective Vlans, how will I admin the switches?

Sorry for the bunch of questions, and thank you for helping.

Kind regards,

Geoff