Nexus 7k and L3 peering

Unanswered Question
Jul 29th, 2010

Hi,

I have a few questions related to the method of  L3 peering between N7k and a generic L3 device (let's say it is a  router) - the idea is to connect N7k to the core network. The current  design is based on Cat6k switches (they are the core of my network)  which have many Vlans and SVI interfaces for them.

EIGRP is also used currently on Cat6k and other L3 devices in my network.

The goal is to extend Vlans from the current Cat6k to  a pair of N7k configured for vPC. To do that I would have to configure  L2 trunks (and NOT to use vPC links) between Cat6k and a pair of N7k and  use them to pass all the current Vlans to N7k. How to establish EIGRP adjajency between Cat6k and N7k and at the same time pass all the vlans? Should I add any new Vlan on N7k/Cat6k, create SVI for it and use it to establish EIGRP peering?

Is the above the correct thinking? if not how to do that?

- One of the design docs say that we MUST use L3 routed interfaces to connect these two devices (N7k and a core network).

- Other ones mention that the _recommended_ way is to  use L3 routed interfaces to connect these two devices ('recommended'  means what? that any other options are available? what are they?)

-  And other ones say that can use Vlan peering (through SVI interfaces)  if only we make sure not to use vPC vlans (peering of routing protocols  using a VLAN also carried on the vPC peer-link is not supported). Does  it mean that if I configure any new/additional Vlan between the core and  the vPC domain + I would exclude that vlan from vPC peer-link that I  can configure EIGRP/OSPF peering between a generic vPC device and vPC  domain???

what about STP root and HSRP? During the migration can they stay on the 6K till I move all my servers from 6k to N7k?

Will the communication be ok? or I can came across the situation that the traffic would be filtered by the peer-link of N7k?

regards,

m.w

I have this problem too.
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Marwan ALshawi Sun, 08/01/2010 - 05:07

if you have a simple topology will be helpful to provide more presice answer

a\however in  general

if you want to use L2 link ( uplink) with N7K it is better to use vPC to utilize both of the links and take the benifit of the usefual feature in terms of having both links in the forwarding state

when you said extended the Vlans using a trunk that imply the L2 domain will be extended in this case where wil be the L3 interface created in the Cat65 or the N7K ?

i would say this will increase the L2 braodcast domain and you need to be careful when configuring Vpc and Non vPC device with extended L2

if you looking to create the SVIs on both of the Cat65 and N7K not sure how this will looks like in your netwrok ( topology will help )

- it is better to use routed interfaces to connect to two L3 devices in ters of equal cost mulitpath whcih will help you to load balnce th traffic using a rotuing protocol and simplifyin your routing peering too

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