servers can't ping each other

[gavin han]

Hi,

I've following topology:

server1(g5/1)<--->4500sw1<---->4500sw2<--->(g5/2)server2

server 1 and server 2 are not able to ping each other. I've verified that routing and switching looks good so far. I need to prove that this isn't network issue, rather it is issue related to server. so, i need to put sniffer, correct? Please advise how should i put sniffer.

should i create span sessions as follow?

4500sw1:

monitor session 1 source interface g5/1

monitor session 1 dest interface g5/3 <--sniffer is connected to this interface

4500sw2:

monitor session 1 source interface g5/2

monitor session 1 dest interface g5/3 <--sniffer is connected to this interface

is that correct? please advise if it is correct or there is any other alternative?

Thanks...

[Jon Marshall]

gavinhan07 wrote:
Hi,
I've following topology:
server1(g5/1)<--->4500sw1<---->4500sw2<--->(g5/2)server2
server 1 and server 2 are not able to ping each other. I've verified that routing and switching looks good so far. I need to prove that this isn't network issue, rather it is issue related to server. so, i need to put sniffer, correct? Please advise how should i put sniffer.
should i create span sessions as follow?
4500sw1:
monitor session 1 source interface g5/1
monitor session 1 dest interface g5/3 <--sniffer is connected to this interface
4500sw2:
monitor session 1 source interface g5/2
monitor session 1 dest interface g5/3 <--sniffer is connected to this interface
is that correct? please advise if it is correct or there is any other alternative?
Thanks...

1) Are the servers in the same subnet ?

2) If they are in the same vlan/subnet how are the 4500s connected to each other ie. via  L2 trunk for example

3) if not can server1 ping it's own default-gateway and the default-gateway for server 2

It's also worth checking whether there are firewalls on the servers blocking the pings.

Jon

[gavin han]

Hi,

yeah, servers are in the same subnet and they are connected through layer-2 trunk. and yeah, they can ping their default gateway too. I believe there is some firewall in the server that's blocking it but i need to prove that it's not network issue.

Would you please advise can I prove it with sniffer as described earlier?

many many thanks...

[Bert Gevers]

Hi Gavin,

if your setup is:

server1<--->(g5/1)4500sw1<---->4500sw2(g5/2)<--->server2

4500sw1:

monitor session 1 source interface g5/1

monitor session 1 dest interface g5/3 <--sniffer is connected to this interface

4500sw2:

monitor session 1 source interface g5/2

monitor session 1 dest interface g5/3 <--sniffer is connected to this interface

This would indeed be the correct configuration on an IOS-based 4500.

These SPAN sessions would show the packets received and transmitted on the link towards resp. Server 1 and Server 2.

Please do verify if server1 has the correct ARP entry for server 2 and vice versa.

If not, you can check the sniffer capture for the ARP request.

If they do have the ARP entry, you should look for the ICMP packets.

HTH,

Bert