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Re: stacking/cascading and routing

 
Dan DeCoursey
Regular Advisor

stacking/cascading and routing

Hello,

 

If I  connect 2 switches together, to increse vlan port density, what needs to be setup.... do these 2 ports have to be "tagged"   or  'trunked" 

 

and since all  my Procurves are L2 devices ...what does or when would you set routing = enabled....

Hers a pinch to grow an inch
1 REPLY 1
Emil_G
HPE Pro

Re: stacking/cascading and routing

Hello,

 

Tagging and trunking are different things and no alternatives you have to choose between. So you can have both at the same time. (I guess the question may have to do with the different usage of the terms by Cisco and HP Provision)

 

Trunking with ProVision means link aggregation. Configuring 2 or more ports to function as a virtual interface, load balancing the traffic between the member ports. If you think that 1 link cannot manage the traffic between the 2 switches  -it is a goog idea to implement trunking. (This is called EtherChannel by Cisco as far as I know)

 

Tagging (as used by ProVision) is needed when you have defined more than 1 VLAN on your switches and you want the inter-switch link to carry this VLANs. Then you can define only 1 VLAN as untagged and the rest of the VLANs should be tagged. (Cisco calls this VLAN trunking, the comware based HP switches as well)

 

So you can configure more than 1 port between the 2 switches (Trunk) and you can configure tagging on the trunk, so the trunk carries multiple VLANs.

 

Regarding stacking: Only the most recent modells of the ProVision based devices support true stacking. The other switches support single IP management stacking which only allows you to manage the stacked switches via single IP address.

 

The 3800 and 2920 series support the true stacking. That is -the stacked devices function like a single virtual device not only regarding the management but also regarding the network protocols. For example one bridge in STP, one hop in routes.

The comware based devices support a stacking feature called IRF.

 

Regarding IP routing:  If your ProCurves are layer 2 devices maybe it would not be possible to enable IP routing at all. Depends on the modell.

You would enable routing when you want your ProCurve device to forward packets between devices in different IP subnets (routing). Typically  different subnets are associated with different VLANs.

The ProCurve switch should have IP addresses in all the subnets/VLANs for which it should route. The clients in the subnets should use the IP address of the switch as default gateway. The switch should have static routes to other routers or a routing protocol enabled in order to be able to successfully route.

So I think the implementation of routing requires some planning and should be done only if you understand what you want to achieve. Enabling IP routing without planning can have undesired results like assimetric routing for example.

There are different approaches regarding where in the network IP routing should be enabled - Core layer, distribution layer or access layer. It also depends on the capabilites of the switches.

 

 

HTH

 

I am an HPE employee

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