Hello Everyone,
I have a problem with ICMP, I have a series of switch in the same vlan (206) this is the admin vlan and then i have a core 6509 who does the inter vlan routing, if a try to do ping from 6509 to another devices, one of them are sucessfuly and the others ones are failed.
for example:
CORE_6509#ping 172.17.0.170
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.17.0.170, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
CORE_6509#ping 172.17.0.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.17.0.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/10/21 ms
CORE_6509#ping 172.17.0.110
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.17.0.110, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/3 ms
CORE_6509#ping 172.17.0.111
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.17.0.111, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
CORE_6509#ping 172.17.0.120
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.17.0.120, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
Like the image showed all are in the same vlan, so I made a debug and this is the answer:
1d00h: IP: s=172.17.200.23 (VLAN206), d=172.17.0.150, len 84, rcvd 1
1d00h: IP: s=172.17.0.150 (local), d=172.17.200.23 (VLAN206), len 84, sending
1d00h: IP: s=172.17.200.23 (VLAN206), d=172.17.0.150, len 84, rcvd 1
1d00h: IP: s=172.17.0.150 (local), d=172.17.200.23 (VLAN206), len 84, sending
1d00h: IP: s=172.17.0.150 (local), d=172.17.0.111 (VLAN206), len 100, encapsulation failed
1d00h: IP: s=172.17.0.150 (local), d=172.17.0.111 (VLAN206), len 100, sending
1d00h: IP: s=172.17.200.23 (VLAN206), d=172.17.0.150, len 84, rcvd 1ping 172.17.0.120
piso5_0#ping 172.17.0.12
1d00h: IP: s=172.17.0.150 (local), d=172.17.200.23 (VLAN206), len 84, sending
1d00h: IP: s=172.17.200.23 (VLAN206), d=172.17.0.150, len 84, rcvd 1
1d00h: IP: s=172.17.0.150 (local), d=172.17.200.23 (VLAN206), len 84, sending
1d00h: IP: s=172.17.200.23 (VLAN206), d=172.17.0.150, len 84, rcvd 1
1d00h: IP: s=172.17.0.150 (local), d=172.17.200.23 (VLAN206), len 84, sending
1d00h: IP: s=172.17.0.150 (local), d=172.17.0.111 (VLAN206), len 100, encapsulation failed
1d00h: IP: s=172.17.0.150 (local), d=172.17.0.111 (VLAN206), len 100, sending1
Looking for some information I found the following:
Encapsulation failed means it doesn't know the layer 2 address of the remote device. In other words, ARP is failing. This could be due to the fact of a misconfiguration on the other side (wrong ip address, interface shutdown) or a misconfig in the layer 2 transit path (STP domain not end to end, wrong VLAN assignments, trunking not configured properly, etc.).
I made the troubleshooting and the interface vla are up, refer to the message encapsulation failed, i found the following:
the ping is not working due to "encapsulation failed". This means that the router knows on which interface it has to send the packet, but does not know how to do it. In this case, you need to understand how Address Resolution Protocol (ARP) works. See Configuring Address Resolution Methods for a detailed explanation.
But i do not how i can resolve the problem, we check stp, vlan, cable. But we have the problem in some sw´s.
Any idea?
Kathy
