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Beginner

FTP traffic configured to use Interface Loopback

Why would someone configure FTP to  use interface Loop back within a routers configuration?

 

Example:

 

Why would someone configure a routers FTP to use a loop back address?
 
interface Loopback0
description Loopback interface
ip address x.x.x.x x.x.x.x
no ip directed-broadcast
!
...
ip telnet source-interface Loopback0
ip tftp source-interface Loopback0
ip ftp source-interface Loopback0
4 REPLIES 4
Hall of Fame Expert

Re: FTP traffic configured to use Interface Loopback

Hello,

the loopback interface is a logical interface that is always up/up if the device is alive.

The loopback interface has to be advsertised and this is the only drawback.

 

Using a loopback interface is so the better way to make the device to use the same Source IP address in accessing services like an FTP server and so on like for example a Radius or Tacacs+ server.

 

So when reviewing activity logs you can always be sure that IP 10.1.1.1 means that specific router and not another one.

 

Loopback interfaces are also very important in networking for example for internal BGP and MPLS and all MPLS based services.

 

Without setting those  source commands the router would use the interface in the path to the destination, that can change for different destinations and can change over time if the primary interface goes down.

 

Hope to help

Giuseppe

 

Beginner

Re: FTP traffic configured to use Interface Loopback

So from what i'm gathering in your post, Loopback interfaces are used

 

As they are always active (up/up)

It can use its self as the source for FTP/Tacacs+ and other services

Ease of verifying its self as the source within logs

 

Am I correct?

Hall of Fame Expert

Re: FTP traffic configured to use Interface Loopback

Hello,

yes your understanding is correct

 

Hope to help

Giuseppe

 

VIP Expert

Re: FTP traffic configured to use Interface Loopback

"It can use its self as the source for FTP/Tacacs+ and other services"

Hopefully you understand the "other services", but for example other devices can use an ACL (or FW rules) to block, or not, traffic using the loopback IP. Also, loopbacks aren't just for traffic sourced from the device they are often used as a management IP for the device too.
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