new VLANs cant ping the default gateway

  noddy_2121 10:29 02 Apr 2009
Locked

Hi all,

I am having a few problems with my new 3com 4500G switch at work.

I have created 3 VLANs on the new 4500G switch, inter VLAN routing works fine on the switch itself. So a host on VLAN 3 can ping a host on VLAN 4 with no problems.

However the problem is when i try to ping a host on the existing network or the default gateway, the ping just times out. Here is my subnet information.

VLAN 2 on the 4500G = 10.69.76.1 255.255.252.0
VLAN 3 on the 4500G = 10.69.80.1 255.255.252.0
VLAN 4 on the 4500G - 10.69.84.1 255.255.252.0

The default gateway = 10.69.72.1 255.255.252.0

The default gateway is a cisco 3750 switch which is connected to a dumb fibre device. We are part of a large enterprise network.

Port 2 VLAN 2 on the 4500G is connected to the cisco 3750.

So communication works fine within the 4500G but i cannot communicate from outside the 4500G!

Just to add i can ping the default gateway (10.69.72.1) from the console connection of the 4500G!

Any suggestions please??

cheers

  brundle 23:04 02 Apr 2009

Which VLAN is your 10.69.72.1 network in? Have you issued the "ip default-gateway" or "ip route" command in your switch config?

  noddy_2121 09:29 06 Apr 2009

the 10.69.72.1 network is in its own vlan on the 4500g. The uplink has got the IP adress of 10.69.75.90/22 which is an IP address from the 10.69.72.1 network.

I have not entered a default gateway in the 4500g, what should this be?

any suggestions please?

  brundle 20:04 07 Apr 2009

Those switches are L2/L3 right? I'm only familiar with Cisco 2x00 switches and routers, but I would guess that the 4500G is doing what a router-on-a-stick config would normally do with less powerful kit - that's where I thought you'd need the ip commands.

The troubleshooting steps here might help; click here

  wazza597 16:25 14 Apr 2009

Hi,

Not sure if you have this working now but I think I might be able to help.

Here is what I understand so far:
Vlan 2, 3 and 4 are working fine on the 4500G as each vlan on this switch has an interface with a ip on it for the inter vlan routing to work. (Correct?)

The connection to the Cisco switch is what I don't understand? You said - The uplink has got the IP adress of 10.69.75.90/22. is this the ip address on the cisco switch? If so it sounds like you will need to put a route on your 4500G which says 10.69.72.0/22 go via 10.69.75.90 (not sure how this is done on a 3com switch as I am a cisco man myself).

To connect these switches together I would normally use a trunk port or I would connect them on a routed link using a different network just for connecting network devices.

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