Can't ping host from switch

[Fabri_Fabri]

(I started a previous discussion but somehow many replies were deleted, I please ask to some moderator to give a look, it was

"Some interfaces/VLAn are not trunking" )

I inherited a Catalyst 3560 (SW1) with many VLANs onto it.

SW1 is connected to a firewall through a trunk port.

I have problems in connecting a host to a particular VLAN.

One working host is connected to this VLAN.

I want to add another host in that VLAN. I configured another interface for that and I connected the new host.

These 2 hosts, same VLAN, can ping each other with no problem.

1° problem: from inside the switch I can't succesfully ping the new host:

switch01#ping 10.1.2.10 <-- WORKING HOST

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.2.10, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

switch01#ping 10.1.2.11 <-- THE NEW ATTACHED HOST

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.2.10, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

What could be the problem ?

Thanks for help.

[Fabri_Fabri]

However, since Catalyst is a layer2 device, I wonder how it was possible that the 2 hosts pinged each other...

[Marvin Rhoads]

They are on same L2 broadacst domain so they will just arp to resolve mac address to IP and then communicate directly - no gateway required.

[Fabri_Fabri]

Mmm .. good point Marvin.

That means that switch had the couple MAC-Ip Address right ? That should also mean that hosts in other vlans could contact that host (because of ARP) but that host could not reply because no gateway.

Correct ?

Thanks.

[Marvin Rhoads]

The switch would not have had the incorrectly configured host in its ARP table (L2-L3 correlation) since it did not have a L3 address in the VLAN.

It would, however, have the host in its CAM (Content Addressable Memory) which is used by the mac-address table which keeps track of MAC address to physical port mapping (L1-L2 correlation).