IOS XR ping failure

[Pavel Bykov]

Hello. I'm fairly new to IOS XR... well, not that new, but I do not understand the following.

I can ping Lo0 interface from the LocationY, and Ping goes both ways, to XR the request, and XR sends the reply back. It all works.

But when I ping from Lo0 on XR to LocationY (So request and reply are reversed) it does not work and returns UUUUU (Unreachable)

This is MPLS network, but how is it possible that communication can work like this? It's same outgoing/incoming interface.

Any ideas how can I start troubleshooting this even? all related interfaces are not in VRFs, all host routes are present.

This is a copy from output:

Ping from location Y to XR works (sending ping from location Y and debugging on XR, on the other side it's all !!!)

RP/0/9/CPU0:PH700-EA2#debug ip icmp

RP/0/9/CPU0:PH700-EA2#LC/0/0/CPU0:Apr 10 14:57:47 : ipv4_io[171]: IPv4 ICMP: TenGigE0/0/0/0: Received echo request from y.y.y.y

LC/0/0/CPU0:Apr 10 14:57:47 : ipv4_io[171]: IPv4 ICMP: TenGigE0/0/0/0: Sending echo reply to y.y.y.y

LC/0/0/CPU0:Apr 10 14:57:48 : ipv4_io[171]: IPv4 ICMP: TenGigE0/0/0/0: Received echo request from y.y.y.y

LC/0/0/CPU0:Apr 10 14:57:48 : ipv4_io[171]: IPv4 ICMP: TenGigE0/0/0/0: Sending echo reply to y.y.y.y

Ping from XR to location Y does not work.

RP/0/9/CPU0:PH700-EA2#show interfaces lo0 | in Internet

Internet address is x.x.x.x/32

RP/0/9/CPU0:PH700-EA2#ping y.y.y.y source x.x.x.x

Type escape sequence to abort.

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

UUUUU

Success rate is 0 percent (0/5)

[Harold Ritter]

Pavlo,

I would start with activating "deb ip icmp" on the XR router and then try the failing ping to see what is the router sending the ICMP unreachable message.

Regards,

[Pavel Bykov]

Thanks, i did that, but the router did not produce any output for the locally originated pings.

But I found out the problem - there is a statefull firewall in the way... ehm...