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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prasad.gsmc Mon, 08/02/2010 - 00:39

regarding Peering

if you have the following proposed setup

6509-----ospf peer---> (Nexus 7K in VPC)

this is not a vaild architecture. You are in need of dedicated routed links between Each 7K to 6K

info from cisco is as follows

"Note When you attach a Layer 3 device to a vPC domain, the peering of routing protocols using a VLAN also carried on the vPC peer-link is not supported. If routing protocol adjacencies are needed between vPC peer devices and a generic Layer 3 device, you must use physical routed interfaces for the interconnection. Use of the vPC peer-gateway feature does not change this requirement. "

http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_2/nx-os/interfaces/configuration/guide/if_vPC.html

Regarding STP

Nexus will be in RSTP+ and it will recognize 6K as root bridge based on Priority. This we have checked. HSRP can be active on 6K.

Please note that during migration you might need 4 physical Ip addres (two for existing 6K and 2 for new 7K) and suggest plan for that.

regards

PK

betacomsvc Mon, 08/02/2010 - 05:45

No. That is not what I need to do. I want to EXTEND Vlans up to N7k. To do that I can't use L3 link.

My idea was to use L2 links WITHOUT vPC between C6k and N7k and use an additional Vlan to establish l3 peering (eigrp,ospf). I would also exclude that vlan from vPC peer-link. To rule out possible split-area failure I would add 1 more vlan to establish l3 peering between N7k-N7k.

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