|
Home > Archive > CCNP > February 2002 > loopback question
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
|
|
| SurfinUSA 2002-02-06, 12:15 am |
| Can someone help me fully understand the loopback interface? What is it used for exactly? Thanks in advance. | |
| Hippo 2002-02-06, 12:39 am |
| 
A loopback interface, is a logical interface configured on a router for the purpose of terminating a telnet seesion, or using it to PING the router for general connectivity testing
It is described as "logical", because it has no hardware associated with it, unlike a serial or ethernet port.
You will find plenty of 'logical' interfaces as you progress through CCNP - BCRAN.
Cheers
Hippo
 | |
| MadChef 2002-02-06, 5:29 am |
| quote:
Originally posted by SurfinUSA
Can someone help me fully understand the loopback interface? What is it used for exactly? Thanks in advance.
As hippo has already explained, it's a logical interface so the line protocol never goes down and removes it as active interface; it's always up. This is what makes it handy. If you have redundancy in your network, you never know what physical interfaces, and therefore their addresses, will be reachable due to circuit issues, hardwar problems etc. A loopback is handy in this case. You can still get to the router even though PVC-1 is down because the route to the loopback now goes over the redundant PVC-2 for example. This makes the loopback an ideal source and destination for things like ntp, snmp, telnet, bgp neighbors, dlsw, stun and bstun peers, etc. It's also used as the router ID in OSPF. Many of my clients also resolve their hostnames to loopback interfaces.
They have so many uses that I believe using them on a consistent basis represents good network design.
MadChef |
|
|
|
|