Routing VLAN over OSPF

Unanswered Question
Jun 9th, 2008
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Hi All,


I have, say, 3 locations, Tokyo (R1), New York (R2) and Sydney (R3) and for this scenario, all are connected via serial, and I am running VLANs at all locations. There is a VLAN named accounting and there is one member at 10.0.1.2/128 on the Sydney side and a member at 10.0.1.120/128 on the New York side. Does this require that I add the network 10.0.1.0/128 to both routers?


router ospf 100

network 10.0.3.0 0.0.0.252 area 0


The links between the 3 main routers will be in area 0. Each lan side of each location, will be in their own areas. Tokyo area 1, New York area 2 and Sydney area 3.


network 10.0.1.0 0.0.0.128 area 1


This is a scenario in a Bosom Simulator only. The network between both routers will be on 10.0.3.0/30. Sydney at 10.0.3.1/30 and NewYork at 10.0.3.2/30


Sydney New York

serial 0/0 serial 0/0

10.0.3.1/30 10.0.3.2/30


Sydney LAN

Switch 1

VLAN 2 Name Accounting

PC 1

10.0.1.2/128


New York LAN

Switch 1

VLAN 2 Name Accounting

PC 1

10.0.1.120/128


There will be another 5/6 VLANs added eventually. I understand that I need to create a trunk between the routers and their respective switch(es) via sub-interfaces. Cheers.


Mark

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n.nandrekar Mon, 06/09/2008 - 01:34
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hi!

As per your configuration, I see that you are having same vlan... say "accounting" on 2 sides of an L3 network. You cannot have the same subnet then. For the Vlan "accounting" to be contifguous and for host 1 (10.0.1.1) and host 2 (10.0.1.2) to talk to each other, you need to have a vlan trunk between the routers (not L3 serial link).

When you have L3 serial link in between, the created "accounting" vlan on both the routers is actually 2 different vlans from practical point ( just the name is same).

As for OSPF, the purpose of network command is "not to advertise the network, but to enable ospf on the link with that network configured" So you need the network command on all the routers. It will then start ospf on the interfaces, discover the neighbor and exchange the LSAs.


Regards,

Niranjan

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