loopback addresses

Unanswered Question
Jun 15th, 2006
User Badges:

when i use a loopback interface, do i need to advertise the address in the routing protocol ? what is the normal way of setting this up, say over a serial , do people always use loopback interfaces, or is this mainly an ospf thing ?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4.5 (2 ratings)
Loading.
vladrac-ccna Thu, 06/15/2006 - 05:17
User Badges:
  • Silver, 250 points or more

is always good to have loopback address.


Not only for OSPF.


"You can specify a software-only interface called a loopback interface to emulate a physical interface. A loopback interface is a virtual interface that is always up and allows Border Gateway Protocol (BGP) sessions, for example, to stay up even if the outbound interface is down.


You can use the loopback interface as the termination address for open shortest path first (OSPF) or BGP sessions. In applications where other routers or access servers attempt to reach this loopback interface, you should configure a routing protocol to distribute the subnet assigned to the loopback address.


Packets routed to the loopback interface are rerouted back to the router or access server and processed locally. IP packets routed out the loopback interface but not destined to the loopback interface are dropped. Under these two conditions, the loopback interface can behave like a null interface.


"


Imagine you have 10 interfaces on your device and you need to test if this device is up and running, would it be best to ping the loopback or a single interface?


loopback will always be reachable if you have at least 1 interface up.


HTH,

please remember to rate helpful posts.


vlad

carl_townshend Thu, 06/15/2006 - 05:24
User Badges:

so is there instances whereas people use the loopback address for there local gateway address ?

vladrac-ccna Thu, 06/15/2006 - 05:32
User Badges:
  • Silver, 250 points or more

Not really.


As you cant put (without bridging) 2 interfaces on the same subnet.


Vlad

carl_townshend Thu, 06/15/2006 - 06:17
User Badges:

but couldnt you use ip unnumbered loopback 0 in the ethernet address to achieve this ?

vladrac-ccna Thu, 06/15/2006 - 06:22
User Badges:
  • Silver, 250 points or more

good point,


Read the last post by Rick


And you'll see that you cant use ip unnumbered under ethernet interfaces



vlad

Actions

This Discussion