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Layer 2 Design Question


HP Blade Enclosure C7000

HP GbE2c Ethernet Blade Switches (x2) [We will call these switches 1 & 2]

Cisco 6509 (x2) Core Switches [We will call these switches A & B]

Current Setup:

The servers in the HP Enclosure have dual NICs that connect to each HP GbE2c Ethernet switch

There is a dual internal cross over link between the two HP GbE2c Ethernet switches (disabled by default)

Each HP Switch has four external uplink ports that you can run LACP to create a trunk port.

I have created a 4x1Gb LACP trunk between HP Switch 1 and Cisco 6509 A

I have created a 4x1Gb LACP trunk between HP Switch 2 and Cisco 6509 B

Cisco 6509 switch A has two 10Gb ports in Port-Channel 1 (trunk) connecting to Cisco 6509 switch B

I am running all Layer 3 routing on the Cisco switches using HSRP


Should I enable the link between the two HP GbE2c switches?  I don't believe you can setup these ports as trunks (i.e. LACP).  Would this create a Layer 2 loop?



Everyone's tags (5)

Layer 2 Design Question

Hey Damien,

I would look into enabling it and tag all vlans needed to provide a complete fault tolerant environment. Are you running NIC teaming on your servers?

LACP and Trunks are two different things...

It will not create a L2 loop provided to you configured STP properly Switch A and B as root bridge primary and secondary respectevely.

The link will be in blocking mode and it will only be moved to a fowarding state if one of the uplinks fail.



Hall of Fame Community Legend

Layer 2 Design Question

Too bad.  IT would've made things slightly easier if your 6500 were running in VSS mode.

Rising star

Re: Layer 2 Design Question

My understanding of the HP Blade switches is that you can configure the backplane links (XConnect1 - port 17 & XConnect2 - port 18) as a port-channel - HP call this 'trunking' which is confusing.  By default 'Trunk Group 1' consists of port 17 & 18, however by default they are disabled.

You state that the 6509 switches are Layer-3 so the I assume the link between them is a routed connection and doesn't have VLANs on it.  If this is the case then you don't need to worry about STP.  The SVI's for the VLAN's for the Blade Enclosure need to terminate on the 6509's and then the L2 VLANs need to be allowed on the trunks down to the Blade Enclosure.  You will obviously be running HSRP, VRRP or GLBP on the SVI's on the 6509's for default-gateway redundancy.  There is no STP loop, just a 'U' shape.

I am not sure VSS would help that much in this case as the two switches in the Blade enclosure are separate switches so the 'U' would need to be through the Core VSS and the XConnects would need to be left disabled (or STP blocked).




Hi Damien  Can you please

Hi Damien
 Can you please tell if your current configuration is working i have one HP GBe2c switch and one cisco 4500 series switch. if possible please share configuration as well. I have tried lacp trunk between HP and cisco on 4 ports but servers in c7000 become inaccessible .


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