Testing out inter vlan routing

adrianm68 · September 2016

Hi There,

I am testing out some inter vlan routing on my Cisco 3550 and having a difficult time getting the windows host being able to ping the vlan ip address. When I turn on debugging for ICMP, it seems the switch receives the ping from the windows host (10.1.20.2), but then proceeds to send the reply to the windows hosts old address when it was on vlan 1:

*Mar 1 00:10:23.371: ICMP: echo reply sent, src 10.1.20.1, dst 192.168.0.249
switch1#
*Mar 1 00:10:28.099: ICMP: echo reply sent, src 10.1.20.1, dst 192.168.0.249
switch1#
*Mar 1 00:10:33.095: ICMP: echo reply sent, src 10.1.20.1, dst 192.168.0.249
switch1#
*Mar 1 00:10:38.099: ICMP: echo reply sent, src 10.1.20.1, dst 192.168.0.249
switch1#

The default vlan1 ip subnet is 192.168.0.0. When my pc is connected to this subnet in any other port, with an IP address of 192.168.0.249, it can see the switch fine. In fact the switch is also connected to my wireless router, and so the PC can surf the internet. So all is goodness.

I created vlan 20, assigned an IP address to the vlan (10.1.20.1) and added the interface to that vlan. Made sure the switchport mode was 'access'. Then I physically swap the pc's ethernet from the vlan1 port to the vlan20 port. I change the IP address on the PC to 10.1.20.2, and delete the arp cache and try to ping the switch (10.1.20.1). I get nothing but timeouts. I have even tried reloading the switch as well as deleting the arp cache on the switch. I still get the same deugging messages above. Routing is on, but that should not matter, since I am just trying to ping on the same network. Any ideas?

some snippets from the config:

interface FastEthernet0/2
switchport access vlan 20
switchport mode access

interface Vlan20
ip address 10.1.20.1 255.255.255.0

adrianm68 · September 2016

Tried this:

switch1#clear arp-cache
switch1#clear arp interface fa0/2
switch1#clear mac address-table dynamic

...and on the pc I tried arp -d *

...and then I tried another ping...
switch1#
*Mar 1 00:50:51.151: ICMP: echo reply sent, src 10.1.20.1, dst 192.168.0.249
switch1#
*Mar 1 00:50:55.987: ICMP: echo reply sent, src 10.1.20.1, dst 192.168.0.249
switch1#
*Mar 1 00:51:00.975: ICMP: echo reply sent, src 10.1.20.1, dst 192.168.0.249

adrianm68 · September 2016

...After a ping

switch1#sh arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.1.10.1 - 0012.7f39.de00 ARPA Vlan10
Internet 10.1.20.2 0 f46d.043a.05ca ARPA Vlan20
Internet 10.1.20.1 - 0012.7f39.de00 ARPA Vlan20
Internet 192.168.0.14 0 0090.a991.0c4b ARPA Vlan1
Internet 192.168.0.1 0 b07f.b9b0.4514 ARPA Vlan1
Internet 192.168.0.249 0 Incomplete ARPA
Internet 192.168.0.254 0 14da.e9f8.d69b ARPA Vlan1
Internet 192.168.0.150 - 0012.7f39.de00 ARPA Vlan1

switch1#sh mac address-table dynamic
Mac Address Table

Vlan Mac Address Type Ports
----

20 f46d.043a.05ca DYNAMIC Fa0/2
1 0090.a991.0c4b DYNAMIC Fa0/21
1 14da.e9f8.d69b DYNAMIC Fa0/21
1 b07f.b9b0.4512 DYNAMIC Fa0/21
1 b07f.b9b0.4514 DYNAMIC Fa0/21
1 ec1f.7291.bdcb DYNAMIC Fa0/21

Simrid · September 2016

Have you enabled routing on your device? Try entering the command "ip routing" and give that shot.

If not, please could you post the configuration for both SVI's and interfaces which are in use and/or perhaps a network diagram of what you are trying to achieve?

adrianm68 · September 2016

I sorted it - removed the ICS from the interface in windows which I was using for GNS3 until I received my new old switch!

Now all I need to do is work out why the switch stuffs up (or rather windows stuffs it up!) when I change the IP address on the windows box (when ICS is running)

I did a test by keeping everything in the native vlan, and changing ONLY the ip address on windows. This stuffed things up the same was as indicated above, even though everything remained in the same vlan.....

Testing out inter vlan routing

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