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New Member

L3 switch to L3 switch

hi,

suppose we have two organizaiton A and B. (both are seperate and have their own intervlan routing) - attached is a visio diagram.

Ospf is turned on on sw A to reach the vlan 10 and 20 from the routed site (192.168.1.x). Similarily Ospf is turned on on sw B to reach the vlan 30 and 40 from the routed site (172.10.1.x).

Now if i have to connect both these switches (Sw A and SW B - both being l3 and running ospf), can i use a l2 trunk link or l3 link. what is cisco best practise design for connecting l3 sw to l3 sw? (i understand if you connect l3 then it makes life easier) but i use l2 trunk then will things work as normal or any special config needed ?

Thanks

6 REPLIES
Cisco Employee

L3 switch to L3 switch

if you just want connectivity b/w Location A and B, just a trunk link would do but if you want the location A vlans to reach location B vlan's then L3 link is recommended and a routing protocol or default route is required across these locations.

will let experts to comment on this.

-Vijay

New Member

L3 switch to L3 switch

Thanks vijay

can i have a trunk link between the both and still run ospf on both switches (is this cisco best practise?) to reach inside networks on both sides ?

Cisco Employee

L3 switch to L3 switch

No it cannot be Trunk. the link connecting both the switches has to be a Routed port to run OSPF between them.

-Vijay

New Member

L3 switch to L3 switch

nope still works with trunk. i have tested this. strange !!

Purple

L3 switch to L3 switch

  Sure it would work as a trunk as long as the vlan has a L3 SVI on each side .  Basically the same as a L3 routed port except you are using an SVI instead of putting the address on the interface itself .

New Member

L3 switch to L3 switch

it does work without svi as well. for example i have vlan 10 on Switch A. if i make the link between Sw A and SW B a trunk and create a vlan 10 on SWB then i can still route through vlan 20 from Sw B. (iVLAN 20 can be reached through VLAN 10 and so as 192.168.1.1.x subnet on SW A

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