How to change outgoing interface loopback ip

[Lei.LIM]

Hello

I want to enable communication between loopback 1.1.1.1 of R1 and loopback 3.3.3.3 of R3.

R1 route 3.3.3.3 255.255.255.255 192.168.1.2
R3 route 1.1.1.1 255.255.255.255 192.168.2.1

It seems to fail because the outgoing interface source is 192.168.1.1.

Can the outgoing interface ip of R1 be converted to loopback ip 1.1.1.1?

[pman]

Hi,

Vios10 (2.2.2.2) needs to know what is the next-hop to destination 1.1.1.1 and 3.3.3.3
try show ip route command on Vios10(2.2.2.2) for 1.1.1.1 and 3.3.3.3.
check whether the Vios10 (2.2.2.2) have routing to 1.1.1.1/32 and also to 3.3.3.3/32.

if not, might it be necessary to add static routings also in Vios10(2.2.2.2):

If everything sets correctly in Vios9 and Vios11 then in the end these will be the routes you need to add in Vios10 for R1/R3 loopbacks:
 - R2 route to R3 loopback: ip route 3.3.3.3 255.255.255.255 192.168.2.2
 - R2 route to R1 loopback: ip route 1.1.1.1 255.255.255.255 192.168.1.1

[Lei.LIM]

HI pman thank you for reply

The physically connected interface pings out into the loopback
R1<->R2
R2<->R1
R2<->R3

However, R1 and R3 that are not physically connected do not have loopback communication.

If R1 and R3 do not set up routing for the physical section connected to R2, ping is possible by setting the source to loopback.

Ex) R1) ping 3.3.3.3 source loopback 0
Ex) R3) ping 1.1.1.1 source loopback 0


Loopback communication is possible by setting up physical section routing connected to R2 in R1 and R3.

Ex) R1) ip route 192.168.2.0 255.255.255.0 192.168.1.2
R3) ip route 192.168.1.0 255.255.255.0 192.168.2.1



I want R1 and R3 to have loopback communication without routing settings.

Is there a way?

[pman]

loopback is a logical, virtual interface. a loopback interface is not a physical interface like Gigabit interface.

eventually, your router needs to know what the next-hop is to which it will route the traffic, the next-hop
is a routing term that refers to the next closest router a packet can go through.

next hop is an IP address entry in a router's routing table, which specifies the next closest/most optimal router in its routing path.

for example, from R1's perspective the next-hop to reach 3.3.3.3 or 2.2.2.2 would be 192.168.1.2

another example, if someone wants to leave a house but all the doors are closed, so he must to open at least one physical door (physical interface) to get out right?

Now I noticed that you wrote Ex, are you using EIGRP or static route?

[Lei.LIM]

yeah 

ex means example

I use only static now

thanks

[Jon Marshall]

No there isn't a way. 

Routing is a hop by hop process so R1 will need a next hop for 3.3.3.3 and that will be 192.168.1.2 (R2). 

You are in effect asking can I have routing work between two routers that are not directly connected without the intermediate router(s) (R2 in this case) having any routes to which the answer is no you can't. 

Jon

[MHM Cisco World]

It can do

[Lei.LIM]

Hi MHM

Can you explain for me? I'm a beginner engineer. Please explain it easily

[MHM Cisco World]

We divide the L3 topology two 
one is global 
other is VRF layer
VRF layer include the both Lo in both Router, 
I already test it BUT I face one simple issue 
GNS3 router dont support VRF selection for return back ICMP<- here I need time to solve it.

[Jon Marshall]

It doesn't really matter whether you use VRFs or not, R1 still needs to have routes to R3 via R2 etc. 

It may be that we are interpreting the question differently but I thought the OP was asking can he ping using the loopbacks without adding any routes for the physical interfaces and the answer to that is still no, whether you are talking about routes within the VRF or the global routing table. 

Jon