cisco Switching and UC540

[jcajuste]

i have a layer 3 switch configure with multiple vlans. i have a uc 540 directly connected to a switch port on the L3 switch.

i can ping the uc.

Core#ping 172.16.15.254
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.15.254, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/8 ms
Core#

however i can't can't traceroute to the uc.

Tracing the route to 172.16.15.254
VRF info: (vrf in name/id, vrf out name/id)
1 * * *
2 * * *

i can traceroute to a device directly in the same vlan as the uc.

Tracing the route to 172.16.15.23
VRF info: (vrf in name/id, vrf out name/id)
1 172.16.15.23 0 msec 0 msec 8 msec

extended ping works 

Core#ping
Protocol [ip]:
Target IP address: 172.16.15.254
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.15.254, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/9 ms
Core#

extended ping works , extended traceroute does not see below.  any help will be appreciated.

Core#traceroute
Protocol [ip]:
Target IP address: 172.16.15.254
Source address: 172.16.15.1
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 172.16.15.254
VRF info: (vrf in name/id, vrf out name/id)
1 * * *
2 * * *
3 * *
Core#ping
Protocol [ip]:
Target IP address: 172.16.15.254
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.15.254, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/17 ms
Core#ping
Protocol [ip]:
Target IP address: 172.16.15.254
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: 172.16.15.1
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 172.16.15.254, timeout is 2 seconds:
Packet sent with a source address of 172.16.15.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/5/17 ms
Core#

[Giuseppe Larosa · Accepted solution]

Hello @jcajuste ,

if UC540 is directly connected traceroute does not add any additional info

post

show ip arp 172.16.15.254

then with the resulting MAC address

show mac address-table address <address> and you will find out where the UC540 is connected to.

However, to answer to your question the UC540 may be configured in such a way that it does not send back ICMP unreachable messages to the L3 switch and this makes the L3 traceroute to fail

Traceroute relies on receiving back ICMP unreachable message of different type TTL expired until a no port on host on final destination host.

Hope to help

Giuseppe