Hi,

I did let me add these 2 sub interfaces. Anyway I have removed interface FastEthernet0/0.100 and checked the gateway is correct too as I can ping 192.168.3.1 from PC B, still the same problem. PC B cannot ping 192.168.2.1 or PC A but can ping the subinterface of 192.168.3.1.

Does the switch need a default gateway?

The default gateway on a layer 2 switch is just to be able to manage the switch from a different subnet than the mgt. vlan is on , has nothing to do with any devices attached to it . Do you have the same native vlan on both the router which appears to be vlan 1 and the 2950 ? On the router try

interface FastEthernet0/0.10

encapsulation dot1Q 10 native

on the switch connection

try

switchport trunk native vlan 10 .

I'm a little confused here. I haven't done anything with the native vlan 1 as I didn't think I was using it, why do I?

Also you only mention adding it to vlan 10 and not 20.

Hello Andy,

in an 802.1Q trunk the native vlan is the only vlan that have its frames sent untagged = without an header 802.1Q.

It is thought to provide backward compatibility to NICs that are not able to use and understand 802.1Q tagged frames.

A mismatch in native vlan can cause IP connectivity issues:

if one trunk side thinks that native vlan is x and the other side thinks is vlan y untagged frames from vlan x are sent and the other side treats them as frames in vlan y and tries to forward them in its vlan y's ports.

In your case I would point to the GW config of the second laptop if it is wrong or missing it could be unable to reach ip hosts in different subnets.

Also Victor's suggestion is good : many and many times users complain of ip connectivity and they have a sw firewall running on the PC.

Here native vlan should be the default one that is 1 but it is not permitted on the trunk on the switch side.

Hope to help

Giuseppe

Hi,

I replaced the laptop with a router with an IP of 192.168.3.10/24 and ip default-gateway of 192.168.3.1 and I get the same problem.

Do my configs look good and do I need to add the native vlan 1 to the router? If so do I add it to all subinterfaces?

Thanks

If you don't add the native vlan to the router it is a default of 1 just make sure the connecting link on the 2950 side is also 1 , if you haven't changed it then it should be 1 by default also , just look at the config on the switchport if it doesn't have a "switchport trunk native vlan X" command then it is 1 by default.

Thanks, do you not see any configs attached, looks like I missed them off.

Here are the configs.

Here are the configs.

Hello Andy,

in order to get better help other info is needed :

on what port is connected the router

I suppose f0/1

on what ports are the PCs/routers

ip addr 192.168.3.x must be in vlan 20

post a sh int fas0/1 switchport so we can check if it is trunking, what protocol is using and what vlans are permitted

Hope to help

Giuseppe

Hi,

As my first post states:

I have a PC (PC A) with:

IP address - 192.168.2.50

Gateway - 192.168.2.1

In FE 0/9 of switch VLAN10

I have a PC (PC B) with:

IP address - 192.168.3.10

Gateway - 192.168.3.1

In FE 0/17 of switch VLAN20

And you are correct the router is in FE0/1

Output:

Switch#sh int fas0/1

FastEthernet0/1 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 000f.2477.0401 (bia 000f.2477.0401)

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 100BaseTX

input flow-control is unsupported output flow-control is unsupported

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:30, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 1000 bits/sec, 2 packets/sec

87 packets input, 11418 bytes, 0 no buffer

Received 30 broadcasts (21 multicast)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 21 multicast, 0 pause input

0 input packets with dribble condition detected

1658 packets output, 120475 bytes, 0 underruns

0 output errors, 0 collisions, 2 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

Switch#