Solved: Re: ip telnet source-interface ....

InternetB · ‎08-21-2008

Hi,

My question is that when I apply this command on R1 'ip telnet source-interface vlan 99' and from the neighbor router, R2 i still can establish telnet session to R1 by telnetting to R1 on vlan 100.

The configs on R1 looks as follows :-

!

R1

--

ip telnet source-interface vlan 99

!

int vlan 99

description Mgmt vlan

ip add 172.16.96.96.1 255.255.255.240

!

int vlan 100

description Inner Rail

ip add 172.16.96.113 255.255.255.240

!

line vty 0 15

login

!

My undertanding to this is that R2 will only be able to connect to R1, via vlan 99 only and not vlan 100. So why is it that I can access R1 via vlan 100 ?

Pls advice,

Cheers,

- InternetB -

Jon Marshall · ‎08-21-2008

Well it can be useful if you need to lock down access to and from devices with access-lists for example. Often on a router you would use a loopback IP address as the telnet source interface.

Also when a router has multiple interfaces some of the IP addresses may not be routable throughout your network so you can pick one of the addresses that can be routed anywhere by specifying it with the source interface command.

Jon

View solution in original post

Jon Marshall · ‎08-21-2008

The "ip telnet source-interface" command is used to tell the router which IP address to use as the source IP address when telnetting FROM that router so if you were logged onto R1 and you telnetted to another device the source IP address would be 172.16.96.1 ie vlan 99 IP address.

But the command does not affect telnet TO R1.

Jon

InternetB · ‎08-21-2008

So which means it is used as the source interface for R1 to telnet to any other device right ?

Hmmmm ....What is the benefit of this ?

Cheers,

- InternetB -

Jon Marshall · ‎08-21-2008

Well it can be useful if you need to lock down access to and from devices with access-lists for example. Often on a router you would use a loopback IP address as the telnet source interface.

Also when a router has multiple interfaces some of the IP addresses may not be routable throughout your network so you can pick one of the addresses that can be routed anywhere by specifying it with the source interface command.

Jon