Unable to ping serial interface from other interfaces of the same router

[r.subramani]

Hi All,

I have a weird problem when in, I am unable to ping a router sub-interface IP address using a loopback or ethernet interface on the same router. Where as the same works on all other routers. Here is the configuration and ping status -

interface Loopback0
ip address 10.9.15.6 255.255.255.255
no ip redirects
no ip proxy-arp

!

interface GigabitEthernet0/0
ip address 10.9.0.59 255.255.255.248
duplex auto
speed auto
!

interface Serial0/0/0:0
ip address 10.9.0.21 255.255.255.252
encapsulation frame-relay IETF
frame-relay interface-dlci 103
frame-relay interface-dlci 777
frame-relay lmi-type cisco
frame-relay local-dlci 103
!

Ping to Loopback interface from Serial Interface IP address

RXYZ#pi 10.9.15.6 source 10.9.0.21

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.9.15.6, timeout is 2 seconds:
Packet sent with a source address of 10.9.0.21
.....
Success rate is 0 percent (0/5)

Ping from Loopback interface to Serial Interface IP address

RXYZ#pi 10.9.0.21 so 10.9.15.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.9.0.21, timeout is 2 seconds:
Packet sent with a source address of 10.9.15.6
.....
Success rate is 0 percent (0/5)

Ping between Loopback interface and Ethernet Interface

RXYZ#pi 10.9.0.59 so 10.9.15.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.9.0.59, timeout is 2 seconds:
Packet sent with a source address of 10.9.15.6
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

pi 10.9.15.6 so 10.9.0.59

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.9.15.6, timeout is 2 seconds:
Packet sent with a source address of 10.9.0.59
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

What more, ping to the serial interface IP address 10.9.0.21 itself fails -

pi 10.9.0.21

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.9.0.21, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

Is this normal behaviour for a subinterface? Can any of you please help me understand this?

Thanks,

Ranganath

[ranjit123]

Hi,

Can u disable CEF on the router, clear cef table and try?

Regards,

[cadet alain]

Hi,

What more, ping to the serial interface IP address 10.9.0.21 itself fails -

This is normal behaviour as you are using frame-relay interface-dlci command so relying on InvARP and if you want to ping yourself you have

to add a static mapping for your IP: frame map ip 10.9.0.21 777

But did you verify your interface was up-up and that you had a mapping and that your PVC was up  ?

sh ip int br | ex una

sh frame map

sh frame pvc | i STATUS

sh frame lmi

Are all these ok?

I would get rid of the local-dlci command as you are using LMI. Why did you force LMI there is no need because of auto discovery.

The other router is not Cisco?

Cdlt.

[r.subramani]

Thanks cdlt.

DLCI 777 is not used. DLCI 103 is the active one. I am not sure why local-dlci is defined (it has been there for ages) and I understand that this used not required on live networks. This circuit is working perfectly. I am not sure of the other end is cisco or not, since it is managed by the ISP. Output of other commands are just fine.

Do you think mapping disabling InvArp will solve? Then we need to add "frame map ip 10.9.0.22 103".

[r.subramani]

Hi Ranjit,

Thanks for the reply. I am not sure if disabling CEF is good option as it might increasing the load on router sustantially. We will try that and clear CEF table during maintanence and see how it works. Will keep you posted about it.

Thanks.

[cadet alain]

So,

the other people from other end told you to use encapsulation IETF and if it works then it's because this is not a Cisco device or they chose to use this encapsulation.

But anyway can you ping other end of circuit?

I've just been labbing a frame-relay topology and I can't ping serial from Loopback  on same router either.

Maybe it's simply not possible, I saw there was an encapsulation problem while debugging so no mapping for destination address( loopback)

but even adding a static one for this failed and I disabled cef on the serial.

Regards

[r.subramani]

Thank you for the testing. Ping to the other end of the PVC is just fine. Now, I am not all alone

May be we got to figure out why it exactly happens. Let me go through few stuff.

Thanks again,

Ranganath