VLAN Issue

[Michael Kline]

I have a 3750 switch with two 48-port switches connected via stacking cable.  On these switches I have two VLANS: VLAN100 for data,  and VLAN300 for Desktop VTCs (dVTCs).  I configured the switch with VLAN 100 having an ip address.

I have verified:
-IP Routing is enabled
-the default gateway is correct
-my trunk port is dot1q encapsulated and passing VLANS 100 & 300. 
-On my Cisco 2951 router, I have created sub-interfaces with IPs and dot1q encapsulation. 
-I am running OSPF and verified that both my data and video networks are being advertised.

Here's the problem:  When I move my dVTCs into VLAN 300, I cannot ping the devices from either the switch or the router.  I am able to ping the VLAN 300 gateway from the switch, but I am not able to ping either of my dVTCs.  When I move the dVTCs into VLAN 300, I see them in the mac address-table, but I cannot see them in the arp table on the router .  The interesting thing is that when I move my two dVTCs into VLAN 100 and move the VLAN 300 sub-interface address to the VLAN 100 sub-interface as a secondary address, everything works great on my dVTCs (I can ping the dVTCs from both the router and switch and the devices show up in my arp table on the router).

I have other campuses where I run the same configuration of VLANs, and everything works great.  I feel like I am just missing something on my switch that I missed in my configuration but I am not seeing it.  I apologize, but I am not able to post my configuration as my network is an isolated DoD network and cannot be posted.  But if you have some ideas for me to check, I would appreciated it.

[Madhukrishnan Gopinathan Nair]

Hi Mike,

Just a quick thought. when you say you see them on mac table, do you see them belong to vlan 300 itself? have you forgotten to define vlan 300 at layer 2.

ie vlan 300 

Thanks,

Madhu

[Michael Kline]

Madhu,

Yes, I have set up VLAN 300 and I show the two dVTCs as belonging to VLAN 300 when I show the mac address-table.  But when I look at the ARP table on the router, I do not see the dVTCs.

If I move the dVTCs to VLAN 100 (my data VLAN), the mac address-table updates with the dVTCs showing being part of VLAN 100 and then my Router shows the dVTCs in the ARP table (and I can ping them)

[Madhukrishnan Gopinathan Nair]

Could you please create an SVI with a test ip from  vlan 300 to see if the router populates the arp table for the SVI. Also we can see if Switch is populating arp for the dVTCs. Logic behind is to isolate the problem on switch or router.

Thanks,

Madhu

[Michael Kline]

I added the IP on VLAN 300 and I am still able to ping the gateway on the router but I still cannot ping the dVTCs themselves.  Also, the router does not show the dVTCs in the ARP table

[Madhukrishnan Gopinathan Nair]

So does the switch populate ARP table?

If not can you please reload the switch and see if it helps.

Thanks,

Madhu

[Michael Kline]

The switch did not populate the ARP table on the router.  I rebooted the switch and the router's ARP table is still not updated to show the dVTCs.

[Madhukrishnan Gopinathan Nair]

The switch did not populate the ARP table on the router. --  Did not understand it

Do you mean , you dont see arp table for vlan 300 on switch ?

Can you please share sh ip route from router and switch &

sh ip arp from switch

Thanks,

Madhu

[Michael Kline]

When I sh ip arp on the router, the only entry I see for VLAN 300 is the sub-interface on the router itself, I do not see the dVTCs.

When I run sh ip arp on the switch, I see the following:

Internet 192.XX.XX.65  Hardware Address ARPA VLAN 100 (.65 is my router IP)

Internet 192.XX.XX.66 Hardware Address ARPA VLAN 100 (.66 is my switch IP)

Internet 11.XX.XX.76 Hardware Address ARPA VLAN 300 (.76 is my SVI IP for VLAN 300 that I assigned)

[Madhukrishnan Gopinathan Nair]

what about sh ip route ..please share

[Michael Kline]

On the sh ip router on the router, I do see:

11.XX.XX.72/29 is directly connected, GigabitEthernet0.0/300

11.XX.XX.73/32 is directly connected, GigabitEthernet0.0/300

But I do not see the Ips for the dVTCs (which is .74 and .75)

[Madhukrishnan Gopinathan Nair]

Can you ping the .76 & .73 from the dVTC and see if it works?

[Madhukrishnan Gopinathan Nair]

while pinging if it is ok, enable debug arp on router

[Michael Kline]

I typed "debug arp" on the router and saw nothing when I pinged either the VLAN 300 sub-interface (ping output was !!!!!) nor when I pinged both of the dVTC IPs (ping output was .....)

[Madhukrishnan Gopinathan Nair]

I requested to ping from dVTC to vlan 300 sub interface

Lets check 1 by 1

1 . Enable Debug Arp on Router

2. Ping switch SVI -- share the result.

3. Ping from dVTC to router vlan 300 sub interface - share result

4. Enable debug Arp on switch

5. Ping Router sub interface(.73) - share result

6. Ping .74 and .75 - share result

share both router and switch debug outputs.

Thanks,

Madhu