What happened if I set ip unnumbered fa0/0 in my serial interface and later my fa0/0 went down?

40 pts.
Tags:
CCIE
Cisco IOS
Cisco IOS Commands
OSPF
My question is simple. what happened if I set ip unnumbered fa0/0 in my serial interface and later my fa0/0 goes down. if I establish ospf in that network which interface will proces the hello packet and which interface via send the hello packet ?. load balance ?

Software/Hardware used:
cisco ios

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If you use “ip unnumbered fas0/0″ on your serial interface and your fas0/0 interface goes down then any packets destined for the that IP address will not be processed and OSPF will drop.
The packets are not processed by the interface per say, they arrive on the interface and then they are actually processed by the RP (processor). If the destination address is a down interface then the router should not process the packet. I have seen some weird behaviour though with this type of topology where only 50% of packets are dropped leading to strange results. Personally I would stay away from unnumbered unless you have a specific reason to use it, like in carrier networks.

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  • Bibs
    Thank you for your reply.... It was really helpfull.
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