IP SLA responder address binding

[franklaszlo]

I can't find this piece of information documented anywhere : when an

ip sla responder

is enabled (disregarding platform), what ip address the service is listening on ?

[MHM Cisco World]

ip sla responder 

one case that this command use when using UDP echo.
I will try do small lab and share here

[MHM Cisco World]

before and after

ip sla responder 

I open UDP 1000 in router R2 to responder to UDP-echo from R1

[franklaszlo]

Thanks @MHM Cisco World but the question is about the listening ip address of the responder, not

ip sla 

configuration.

It goes without saying that a router in prod will have a a dozen of ip address assigned to various interfaces. Will the

 IP SLA responder 

listen on all of them ? I certainly don't want it to listen on an address set up on an interface for BGP peering for instance. So how to bind the responder service for a given address / interface only ?

[paul driver]

Hello
When you set up a responder it should show the statistics what ports it should except
As for the sla sender, you can specify the port to send the sla probes on

rtra (1.1.1.1)
ip sla responder

sh ip sla statistics
sh ip sla responder

rtrb (2.2.2.2)
ip sla 10
udp-echo 1.1.1.1 12000 <----specify port
ip sla schedule 10 start-time now life xx

[MHM Cisco World]

see below commnet

[franklaszlo]

@MHM Cisco World thanks for the update.

In your post the router prompt in console view is only visible for R2 (responder), so I assume the other one to the right is for R1, also because you mention "the trick is in R1 disabling the control".

Said that, your example shows an

ip sla operation

configuration on R1 for ip sla 10. I understand that R1 will not use the control protocol to negotiate the port for the operation and directly query 10.0.0.2:1000, but it is unclear what effect the configuration on R1 has on a different router - R2 - where the responder is set up ? Also, I can't see the configuration of the responder in R2 only the output of

show ip sla responder

To clarify, could you please share both routers

ip sla configuration

in your example ?

[MHM Cisco World · Accepted solution]

R1 config 

R2 config

with 

ip sla responder (only in R2)

R1 not disable Control 
the R2 in this case will open port when receive UDP control message from R1, R1 ask R2 to open specific port 

this what you dont want because when R2 receive any control message it open port and all interface can listen to that port.

BUT 

ip sla responder udp-echo ipaddress <IP-R2> port < port>   this in R2

ip sla 10
udp-echo <IP-R2><port> source-inteface <IP-R1> source-port <port-R1> control disable 

here the R1 will not send ask open port and R2 not config to open port because the control is disable.
R1 send immediate UDP traffic and since we config R2 with source and port for reply the R2 will reply to UDP-echo.
in R2 other  interface will not listen to port and not reply to UDP-echo