3560 communication problems

Answered Question
Feb 11th, 2008

I have a brand new 3560, that I have configured to replace an existing 2651 router. I am using ports 23 and 24 to do this. Port 23 is setup to connect to my firewall, which is a server box, with Checkpoint installed. Port 24 is setup to connect to a port on an HP 4108gl chassis. When I plug the cables in for the new switch, there is no communication. I cannot ping the 3560 from the firewall, and the HP never picks up the MAC address of the 3560, and no ping from either side of the connection. I have the configs of the original 2651, and the 3560, if anyone wants to look at them. I am really banging my head on this, so any help would be greatly appreciated.

My e-mail is jheaton AT etp.ca.gov if anyone would like to see the config files.

I have this problem too.
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Correct Answer by Jon Marshall about 8 years 11 months ago

Hi Joe

Apologies, missed your reply. Have you checked the speed/duplex. If in doubt hardcode both ends and see if that helps.

Also can you post routing table from your router and the 3560 (if you can get them from both devices)


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Overall Rating: 5 (2 ratings)
srue Mon, 02/11/2008 - 10:05

can you post the interface configs for ports 23/24. Can you be more detailed about what you're trying to ping? Is it a VLAN interface? which one? are the servers/firewall on the same VLAN as the interface you're trying to ping?

joeheaton Mon, 02/11/2008 - 10:17

Yes, there are 4 VLANs that will be coming through this port. The port connecting to the firewall is not on a specific "VLAN". Anyway, below are the configs for the 2 ports, and an example of a VLAN config.

interface GigabitEthernet0/23

description **Connection to C4000-Public**

no switchport

ip address


interface GigabitEthernet0/24

description **Connection to HP-4108**

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 10,20,30,40

switchport mode trunk


interface Vlan10

description **VLAN-10-UPPER**

ip address

ip helper-address

The other VLANS are going to different public subnets, with the same helper address. I put in the allowed statement this weekend, although I was told it really wasn't needed.

joeheaton Mon, 02/11/2008 - 12:42

Anyone have any ideas on this? I really think it's something to do with the 3560, as everything starts working again when I put it back to the router. As far as the pinging question:

1) I log into my firewall, and am not able to ping port 23 of the 3560, which is manually configured with an IP address.

2) I telnet into the HP switch, and try to ping the IP of VLAN10, which I was thinking would be assigned to port 24 of the 3560.

3) I console into the 3560, and cannot ping the HP switch, or the firewall.

Really banging my head on the wall as to what the problem with this is, so any help would be greatly appreciated.

Jon Marshall Mon, 02/11/2008 - 12:57


Can you check that you have ip routing enabled on the 3560. Quickest way to make sure it is on

3560(config)# ip routing

Also make sure you don't have a default-gateway configured on the 3560. You should have a default route but not a default-gateway.



joeheaton Mon, 02/11/2008 - 13:06

yes, IP routing is in the config.

Yes, I have a default route:

ip route

no, no default gateway.

Jon Marshall Mon, 02/11/2008 - 13:07

Okay, thanks

Can you verify whether the links are actually showing up on the 3560 ?

Also can you post the config of the 3560 + the output of a "sh vlan".


joeheaton Mon, 02/11/2008 - 13:19

I'm attaching the config for the 3560, and the output of the sh vlan command. That was an interesting one, as it doesn't show any vlans besides the default one...

Jon Marshall Mon, 02/11/2008 - 13:26


You need to create your vlans at layer 2 ie.

3560(config)# vlan 10

3560(config-vlan)# name v10

At the moment you have L3 vlan interfaces but no layer 2 vlans.


joeheaton Mon, 02/11/2008 - 13:32

Fantastic. I will award you with massive points as soon as I'm able to test this, if it works. Thank you so much for your help.

joeheaton Mon, 02/11/2008 - 13:49


One more question. Do I need to assign Gi0/24 to each of the 4 layer 2 VLANs I just created? Or is that done automatically?

Jon Marshall Mon, 02/11/2008 - 13:50


Gi0/24 is configured as a trunk so once you create the vlans at layer 2 then your trunk should be fine as long as you have configured the other end as a trunk as well.


Jon Marshall Mon, 02/11/2008 - 13:51

One other thing. This does not explain why your L3 port cannot ping the firewall unless of course the firewall is blocking pings.


joeheaton Mon, 02/11/2008 - 13:54

That may actually be the case, as right now, from the router, which is working, the firewall is not replying to ping.

joeheaton Wed, 02/13/2008 - 14:31

Unfortunately, Tuesday was a state holiday, so my boss wouldn't let me come in and implement. I'm not going to be able to try until Friday now... That was the only problem you saw in the config though, right?

Jon Marshall Thu, 02/14/2008 - 14:41


Can't see anything else wrong in config. As long as you are sure the port on the device on the other end of gi0/24 has also been configured as an 802.1q trunk.


joeheaton Thu, 02/14/2008 - 15:54

The other side is an HP 4108 switch chassis, and the port is TAGGED for all VLANs, which is the same thing as what Cisco calls trunk...

joeheaton Fri, 02/15/2008 - 17:59

No joy on this project yet. I'm attaching a traceroute and constant ping. First is with the switch, and the second is with the original router. We're getting through, but lots of packets are getting dropped. Internet was working with the switch in place, but extremely slow. We're really close, and to be honest, I'm not even sure the problem is with the 3560 at this point, but if you can think of anything else to try, please let me know.

I'm going home for a 3-day weekend, so I'll check back here on Tuesday. Thanks for all your help, and hopefully we can get this thing working...

joeheaton Tue, 02/19/2008 - 07:31

Bump... anyone have any ideas? I'm thinking port speed mismatch maybe, but I'm not sure.

Correct Answer
Jon Marshall Tue, 02/19/2008 - 12:25

Hi Joe

Apologies, missed your reply. Have you checked the speed/duplex. If in doubt hardcode both ends and see if that helps.

Also can you post routing table from your router and the 3560 (if you can get them from both devices)


joeheaton Tue, 02/19/2008 - 12:51

Attached is the routing table from the 2651. The table is blank at the moment for the 3560, since there's nothing connected, but I'm pretty sure it looked very similar to this one.

The port speed is what came to my mind first also, but I just wanted to see if there were any other "gotchas" to look out for.

joeheaton Thu, 02/21/2008 - 15:27


Can you think of anything else that could be causing my situation besides port speed/duplex issues? I'm going in on Saturday to try one last time before my boss calls in outside help. I'd really like to be able to get this thing going on my "own" (with your help and a couple others that have helped...hehe)

abelardo.gonzalez Fri, 02/22/2008 - 07:15

does the interfaces are enable?

run this command, show interface status, see if the interfaces status, is must be connected, check for the duplex and speed status

does LEDs are on or blinking state?

see the speed and duplex configuration for the server and configure the same on switch port 23 and 24

if you are working with vlans run the show vlan command and check if all port are configured in the same vlan where you are working for


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