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Core layer switches IP address for routing

For routing process I add a IP address of each Vlans subnet that active on each Access and Distribution switches (Have a port with that Vlan on the switch) to the corresponding Vlan Interface of them.

Which IP address should I add to the Core switch for routing?

Should I add a IP of each vlan that in the LAN to each vlan interface of Core layer switch?

I want run OSPF routing protocol on the LAN.

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Re: Core layer switches IP address for routing

Hello Reza,

>> Which IP address should I add to the Core switch for routing?

if you want to implement a L3 routed core every link betweeen core device and a distribution device is a L3 link with its own IP subnet.

For example if you have 16 distribution pairs and two core switches: dis11 to core1 di12 to core2 dis21 to core1 di22 to core2

... disF1 to core1 disF2 to core2

this under the idea to have not a full mesh between core routers and distribution devices

then you need also a L3 link between the two cores (at least one)

Each L3 device should also have a loopback interface to be used as OSPF router-id and for management purposes (telnet and so on)

you can use /32 loopbacks taken from same block for example core1 core2 dis11 dis12

to make the routing function the core switches have to talk OSPF on all links to distribution nodes

router ospf 10


network area 0

network area 0

network area commands work like ACL statements and first statement starts OSPF on each interface whose ip address belongs to 10.10.10/24 space

Second command is used to advertise its own loopback.

router-id command allows to define the OSPF router-id.

Distribution nodes have to advertise client Vlans and to take part in OSPF communication on point to point link.

if you use a L2 access layer design client vlans are served by distribution nodes.

if you use a L3 access layer design the access layer switches take part in OSPF and have to advertise their own client vlans.

Hope to help


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