How to ping from loopback interface of router

[mirror512]

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

[ajay chauhan]

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.

Ty

[mirror512]

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

[ajay chauhan]

You will have to configure telnet frist time.

Ty

[darren.g]

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

[shiramat]

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

[Oleksandr Nesterov]

Sagar

Try to execute:

R1# ping

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

HTH,

Alex

[shiramat]

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

[Oleksandr Nesterov]

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

[shiramat]

Hi Alex,

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

regards,

Sagar

[Oleksandr Nesterov]

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

[shiramat]

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

[franklinbrown749628471]

shiramat config works in Packet Tracer.

[franklinbrown749628471]

Oleksandr is correct and it will work in Packet Tracer.

[franklinbrown749628471]

Extended Ping from a loopback address.