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New Member

route on addtitinal vlan

I have an ABR in my premise...

Originally I have on my LAN an IP address BLOCK1.

Now, we are planning to add another block called BLOCK2 and planning to do 2 VLAN on our core switch ..One vlan for the old block and another vlan for the new block..the core switch will provide inter vlan routing..This 2 blocks cannot be summarized as 1 summarization...

What command will i use on the ABR to reach the new Block 2 adresses.

I was planning to inject a static route below

IP route IP_Block 2 IP_vlan old

Where ip_block 2 is the summarize IP of the new block

and IP_vlan old is the Ip address of the vlan(Block 1) which is connected to the interface of the router.

Thanks a lot


Re: route on addtitinal vlan

Doesn't ABR and your core switch speak OSPF?If not you can use the same method that you use for your old vlan (I don't know how you did it:)).


New Member

Re: route on addtitinal vlan

i just called the old lan as old vlan but it is actually a flat network..on the abr, that network is mentioned on the network statement..but since we are implementing now the vlan because of the additional network, could i use the static route ive stated b4?


Re: route on addtitinal vlan

I think In your old topology ABR was directly connected to ABR and therefore "network...area..." statement under OSPF config of the ABR was OK. But now you say you'll perform inter-vlan routing on the core (can I say layer-3) switch. This way you'll break the connection between ABR and the subnets (there'll be a new subnet between ABR and layer-3 switch). Solutions I can imagine:

1. Make your layer-3 switch part of the OSPF area bounded by the ABR. - I think the most appropriate way.

2. You can extend you vlans to the ABR via a trunk and put network statements for both subnets. But this way you won't use layer-3 sufunctionality of the switch and the ABR will take the load of inter-vlan routing.

3. If the layer-3 switch doesn't support OSPF you can perform inter-vlan routing on the layer-3 switch, write two static routes to your subnets on the ABR and resistribute these routes to OSPF. But this way your ABR will be an ASBR also.

Good luck.

New Member

Re: route on addtitinal vlan

Nice info..Thanks a lot. I might stick to your solution number 3, because theres a plan to insert firewall near future (which we know doesnt support ospf)..Isnt static route on the ABR good enough to reach my vlans without using not well verse in redistribution thats why i want to eliminate that portion if possible at all..

Re: route on addtitinal vlan


If you write statics on the aBR and don't redistribute it into OSPF, of course ABR can reach those networks but ABR won't form external LSAs for these networks and so rest of the OSPF domain will have no knowledge about these and can't reach these.

If you write statics on the ABR you can't put the "network" commands like the way you do up to now because these networks are not directly connected to the ABR anymore ("network...area... " can be written for directly connected networks). With this configuration you'll have a new network connecting switch and ABR (probably a /30 mask network).