Which ip address should we assign to the loopback interface?? 
Easy question!
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Which ip address should we assign to the loopback interface??
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{ 7 comments… read them below or add one }
It depends on your requirement if your are using this loopback for OSPF then it should be /32. and if you are using this for publishing any network like in a lab environment then you should use subnetmask accordingly.
umm, to be the source address for the tacacs request to the AAA server, i used 1.1.1.1/32 but it seems routing problem when the AAA try to send its rsponse
Any /32 from within your network…. Make certain you have a network statement in OSPF “covering” the loopback, if you intend to use it to route stuff to.
If hosts from outside your network are trying to connect to this loopback address, shouldn’t you use a public address on it? 1.1.1.1/32 is a public address, but is it a part of the space you actually can use?
it not from my subnets range
. actually i can use any ip address but i will advertise this IP, right?
Any IP address you choose must be advertised to be reachable, yes…. But, if the advertised IP address is leaving your network, either use an agreed upon private address, or something out of your public range. Otherwise, you might conflict with some other address, making your address unreachable. In any case, it’s not polite to step on someone else’s address space (hijack it). In fact, one reason why this host may not be reachable from outside your network, if that’s where you’re trying to reach it from is the address you’re advertising may be filtered out, uRPF’d, etc.
Perhaps you could explain a bit more about what it is you’re trying to do (?), so we could help you choose the righ IP address/etc.
Sure i will not choose IP address used by another one, In fact even i did, it is not a problem because as i know that we have some subnets at our region and only these subnets are advertised and the ISP will not advertise this IP,else if set IP address within our subnets, right?
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