high availablility core network design questions

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Apr 28th, 2008
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I have a question concerning a high availability design.


We are running OSPF internally, all in the same area.


My questions are concerning the etherent connections in violet.


In our network, internally, all router ethernet interfaces are in the same vlan and subnet. At the moment, we only have etherent A in place.


Would the way to make this redundant connection on the MPLS router involve just have interface A in the existing router subnet and create a new router subnet for interface B, or possibly subnet a two host network out of the existing router subnet?


What I am getting at, is that if we are using dynamic routing (OSPF) and the router will not allow more than one interface in a subnet, the second connection will have to be in a different subnet, is this correct?


And our setup requires that we prioritize the one connection (A) over the other(B), would this be done with increasing the cost of one connection over the other, or a more common or sophisticated way of doing this?



Also, since the ASA appliances will be one active, the other standby, we need to prioritize Ethernet A over B there as well.


We have a block of 32 addresses, would we subnet the two etherent interfaces there, maybe two host subnets?


We still need to route the rest of the address block to the outside interface of the ASA appliances?


Any reply would be appreciated



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tstanik Mon, 05/05/2008 - 06:08
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Yes, in the dynamic routing OSPF the router will not allow more than one interface in a subnet, the second connection will have to be in a different subnet.


The cost (a link-state metric) of sending a packet through an interface. This is an unsigned integer value from 0 to 65535. 0 represents a network that is directly connected to the interface, and the higher the interface bandwidth, the lower the associated cost to send packets across that interface. In other words, a large cost value represents a low bandwidth interface and a small cost value represents a high bandwidth interface. So you can give the priority from the cost.


The ospf cost command lets you explicitly specify the cost of sending a packet on an interface. The interface_cost parameter is an unsigned integer value from 0 to 65535.

The no ospf cost command lets you reset the path cost to the default value.


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