topic How to ping from loopback interface of router in Routing and SD-WAN

How to ping from loopback interface of router

mirror512 — Mon, 04 Mar 2019 21:26:35 GMT

I have seen the lab for CCNP ROUTE exam it stataes that you must aable to ping and telnet from loopback interface 101 on R1 to ip address like 172.1.1.1

Now is that ping different from normal ping. because ping command is same i think

How to ping from loopback interface of router

ajay chauhan — Mon, 29 Aug 2011 15:31:06 GMT

Normal ping use the IP of outgoing interface and from loopback means extended ping where you will have to mentioned the source interface and source ip will be the IP of that interface.

How to ping from loopback interface of router

mirror512 — Mon, 29 Aug 2011 15:37:31 GMT

thanks ajay ,

One thing more , when they say you should be able to telnet

What i am supposed to do do then

I mean unless there is access list , if i can ping , what can be the problem with telnet

or do i have set vty password on destination router so that telnet is successful

How to ping from loopback interface of router

ajay chauhan — Mon, 29 Aug 2011 15:49:56 GMT

You will have to configure telnet frist time.

How to ping from loopback interface of router

darren.g — Tue, 30 Aug 2011 00:22:46 GMT

Contra MK wrote:

I have seen the lab for CCNP ROUTE exam it stataes that you must aable to ping and telnet from loopback interface 101 on R1 to ip address like 172.1.1.1

Now is that ping different from normal ping. because ping command is same i think

You can PING with the source IP address of any interface configured in the router by using the following command format

ping source

where w.x.y.z is the IP address you want to ping, and a.b.c.d is the source IP you wish to use.

You can also do

ping source loopback 0

to send the packets with the source IP address of the loopback interface.

Note that in all cases the source IP address (be it another interface or the loopback IP address) must be either in the routing table of the remote router, or covered by a default route on the remote router, or the packets won't return.

Cheers

How to ping from loopback interface of router

shiramat — Mon, 04 Feb 2013 15:16:50 GMT

Hi Darren,

Is it possible to use this command "ping source loopback 0" on packet tracer 5.13?

I tried to execute this command with no success.

"Router#ping 172.16.1.1 source lo0

% Invalid input detected at '^' marker."

Any suggestions? M i missing anything here?

Thanks,

Sagar

How to ping from loopback interface of router

Oleksandr Nesterov — Mon, 04 Feb 2013 16:40:00 GMT

Sagar

Try to execute:

R1# ping

router should enter to "extended ping" mode where you can configure source interface.

HTH,

Alex

Re: How to ping from loopback interface of router

darren.g — Wed, 06 Feb 2013 20:47:29 GMT

>"Router#ping 172.16.1.1 source lo0

> ^

That's indicating the "ping" command is not recognised at all, not the arguments. Are you sure the ^ is appearing after the "ping"? What happens if you type

ping?

How to ping from loopback interface of router

shiramat — Thu, 07 Feb 2013 02:45:29 GMT

Hey Darren,

First of all i'm trying to ping from a loopback interface to an IP address of the router interface.

Yes as per the previous post of you, i executed the command "ping 172.16.1.1 source loopback 10" as you see from the above image.

-> When i execute this, i get:

R3#ping 172.16.1.1 source loopback 10

% Invalid input detected at '^' marker.

-> If i type ping? i get:

R3#ping ?

WORD Ping destination address or hostname

ip IP echo

-> If i execute ping normally like this:

R3#ping 172.16.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 2/3/6 ms

it goes fine, which is the ping from one interface to another

So is there a different method of how we execute ping command from a loopback interface?

Please advise.

regards,

Sagar

How to ping from loopback interface of router

shiramat — Thu, 07 Feb 2013 03:04:57 GMT

Hi Oleksandr,

If i enter "R3#ping " i get like this:

R3#ping

Protocol [ip]:

can you please let me know what do i enter here? I have tried entering IP address, Loopback's IP address, but always get a message: "% Unknown protocol - "10.10.10.3", type "ping ?" for help"

Please see the below screen shot for reference:

i'm trying to ping from the loopback interface 10 to 172.16.1.1.

thank you!

Sagar

How to ping from loopback interface of router

Oleksandr Nesterov — Thu, 07 Feb 2013 08:20:19 GMT

Hi Sagar

in the squeae brackets device gives you a default option - in your case it's ip protocol. So ping will be used for ip protocol.

Rt#ping

Protocol [ip]: ip

Target IP address: 10.0.0.1

Repeat count [5]: 5

Datagram size [100]: 100

Timeout in seconds [2]: 2

Extended commands [n]: n

......

Alex

How to ping from loopback interface of router

smitesh kharecha — Thu, 07 Feb 2013 08:25:52 GMT

Hi Sagar,

Not sure about the packet tracer, but following are the options which you can use on router / switch.

Option 1: ping x.x.x.x source lo0

Option 2:

PING IP

Target IP address: x.x.x.x

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]:

Re: How to ping from loopback interface of router

paul driver — Thu, 07 Feb 2013 08:44:06 GMT

Hello Sagar,

It sounds like the IOS ( software) of the router is a old version which doesn't include this way of specifying source.

Try using the extended ping.

Ping (press enter)

Protocol [ip]:( press enter)

Target IP address (enter target address)

Repeat count [5]:( press enter)

Datagram size [100]:( press enter)

Timeout in seconds [2]:( press enter)
Extended commands [n]: Y

Source address or interface: loopback10 ( press enter)

Type of service [0]: ( press enter)

Set DF bit in IP header? [no]:( press enter)

Validate reply data? [no]:( press enter)

Data pattern [0xABCD]:( press enter)

Loose, Strict, Record, Timestamp, Verbose[none]:( press enter)

Sweep range of sizes [n]:( press enter)

res

Paul

Being able to

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Re: How to ping from loopback interface of router

paulstone80 — Thu, 07 Feb 2013 13:05:28 GMT

Hi Sagar,

I think this may be a limitation within Packet Tracer. You don't get the full IOS within the PT devices, and a lot of commands and extended command features are missing.

What output do you get if you type: ping 172.161.1.1 ?

HTH

Paul

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How to ping from loopback interface of router

shiramat — Thu, 07 Feb 2013 14:32:45 GMT

Hi Paul,

thanks for the reply.

I'm trying to ping from loopback 10 to 172.16.1.1.

so target IP address would be 172.16.1.1

when i enter Y in extended commands, i'm able to enter only 172.16.1.2 as Source address / interface. It is not taking the loopback10 command neither its takes the 10.10.10.3.

Also how we will know from which loopback address are we pinging if it doesn't allow loopback ip address but allows to enter 172.16.1.2, which is the main interface?

Seeing that it allows only main interface ip address, it seems that it is how the s/w is designed by default, if you can make me understand on this, that would be awesome!!

thanks,

Sagar

How to ping from loopback interface of router

shiramat — Thu, 07 Feb 2013 14:34:21 GMT

Hi Paul,

if i type: ping 172.16.1.1, its get successful

R3#ping 172.16.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 2/3/6 ms

thanks,

Sagar

How to ping from loopback interface of router

shiramat — Thu, 07 Feb 2013 14:38:25 GMT

Hi Alex,

thanks, that works.. But my query is that, how we know which loopback address are we pinging from?

regards,

Sagar

How to ping from loopback interface of router

Oleksandr Nesterov — Thu, 07 Feb 2013 14:58:09 GMT

Sagar

First - you can run "debug ip icmp" to see icmp packets which will be sent from your box.

And If in the following line you will type y:

Extended commands [n]: y

you will enter to the extended mode and will be able to set souce interface

not sure whether this is supported in packet tracer, but worth to try

HTH,

Alex

How to ping from loopback interface of router

shiramat — Thu, 07 Feb 2013 16:28:00 GMT

Hi Alex,

I made it. Thanks a lot.

The problem was with configuration. I had configured loopback 10 on a wrong interface.

I applied access-lists to prevent host loopback 10 from reaching 172.16.1.1 and got the o/p successfully.

R3#ping

Protocol [ip]:

Target IP address: 172.16.1.1

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface: 10.10.10.3

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

Packet sent with a source address of 10.10.10.3

UUUUU

Success rate is 0 percent (0/5)

the access-list worked.

Thank you for bearing with my silly questions.

One more question, can you please let me know if there is virtual software better than PT that has more advanced features?

regards,

Sagar

How to ping from loopback interface of router

shiramat — Thu, 07 Feb 2013 16:30:48 GMT

Hi Paul,

it worked, i could get it done. Its just that i had configured loopback 10 on a wrong interface.

regards,

Sagar