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Should I use OSPF and make the firewall and ABR?

Hi all,

I am designing an almost isolated network which consists of a VPN stack (a firewall + router) connects to another firewall which hosts all these VLANs that connects to a layer 2 switch (attached is the raw diagram).


so for routing should I just use default route and send everything behind the firewall (internal subnets) up to the firewall and then up to the stack (which does dynamic routing) or use OSPF on the firewall one area for behind the firewall (internal subnets) and another one in front of it (area 0) which connects to the stack?

also there will be other networks accessing this network through VPN (those connection also will terminate on the VPN stack).






The diagram is not quite clear to me. The "VPN stack" look like a one-arm connected VPN appliance, but not clear to show if it's a site-to-site VPN or remote-access VPN? If it's site-to-site VPN, how many sites are connected? Is the OSPF already been enabled on the "VPN stack" and have OSPF neighbors with other sites?


From your diagram, everything look very simple...(e.g. no resilience path, no resiliecne device, only 1-way-in 1-way-out) I can't see a strong reason to use OSPF on your internal firewall. So, more information is needed.



paul driver
VIP Mentor


looks like you only have a single exit from the internal fw to the vpn firewall-rtr as such static default route would be applicable here pointing to the lan interface of the vpn stack because the vpn stack will be dealing with the dynamic routing you wouldn’t need any on the internal fw

However this would then mean the vpn stack would require static or summary routes for your internal lan subnets pointing to you internal fw unless the vpn stack is performing NAT

So if you don’t won’t to mess around with static routing the simple ospf stub area peering between the vpn stack and the internal fw would  be applicable so the vpn stack would advertise a default route into the stub area of the internal fw and at the same time dynamically learn the lan subnets 

vpn stack
wan interface- ospf area0
lan interface-opsf area1 stub no summary

internal fw
wan interface-ospf area1 stub
advertise lan subnets 


kind regards

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