Packet loss when pinging internal router interface?

[jtb]

Somewhat strangely we are experiencing packet loss when we ping the IP address of a 7204VXR's internal interface from that router itself.

The port adaptor is a "T3+ PA" type with 2 DS3 ports. Rate limiting has been removed from this interface to help troubleshoot this problem.

I have included some output from the show diag command below, thanks for any help anyone can offer.

Hardware revision 1.0 Board revision B1

Serial number 21704129 Part number 73-3761-02

Test history 0xE RMA number 00-00-00

[svermill]

How is your cpu, memory, etc? I don't think that an internally generated ping gets much priority by the cpu so it may be that your packets aren't being lost so much as ignored. Just one of a thousand possiblilities.

[jtb]

The router is in good health, CPU typically 10-15%, and it has 256mb of memory of which only about half is used on average.

[svermill]

Dang it.

Have you done any debug (icmp, serial interface, etc)? Can you open a TAC case?

Have there been any recent config changes? Just yesterday, on another forum, someone deleted a subinterface without removing the IP address first. The router tried to load balance accross the deleted interface - resulting in every other ping packet being sent into the infamous black hole. I realize that probably isn't anywhere close to your situation. But it does illustrate the weird and unexpected things that can happen as a result of seemingly innocent config changes.

Just a though.

[glen.grant]

have tried pinging thru the interface to see if you are still seeing drops . We just had a problem with a 6509 that sounds strangely similar , ended being supervisor card problem .

[ashok_boin]

Hi,

If it is the Point to point link interface, then first try ping for other end interface IP address. If that works fine, then may be bad link or congestion which is giving the packet loss. And one more thing, in point to point side, if you try to ping to internal interface address, then the process is like this. R1(your) and R2(remote). Ping request travels to R2 and then back to R1, then get a reply from your router and that reply returns through R2 to R1, then only your router considers that's a reply. And try with extended ping command by increasing time delay.

Hope this helps..

Regards...

--Ashok.

[robert.yarush]

Ive seen this before... but attributed the issue to provisioning of the circuit. I have a DS3... point to point between two router devices.... and when I do an extended ping.... it pings fine at the default 100 byte  packet size.... but when I bump up to 1024.... I get the following:  I cannot figure out why the packet loss.

Sending 100, 1024-byte ICMP Echos to 143.69.250.49, timeout is 2 seconds:
!!!!.!!!!.!!!!.!!!!!!!!!!!!!!!.!!!!.!!!!.!!!!.!!!!!!!!!!!!.!!!!.!!!!.!
!!!.!!!!.!!!!.!!!!.!!!!.!!!!.!
Success rate is 84 percent (84/100), round-trip min/avg/max = 9/78/1076 ms.