11-12-2009 12:38 PM - edited 03-06-2019 08:35 AM
I had posted this issue before, then a Tomcat issue obliterated my post. So I'm back, this time with a diagram that I hope helps. This really has me stumped, and my VAR has not been able to fix this either.
I am in Building A. I have a PC that is connected to a 2950, which is connected to a 3560. Off the 3560 is my server running DHCP. We are in VLAN 11, so we would expect the PC to get an IP address in the 11 range.
The 3560 has a fiber link that takes it to the main 3560G, which is doing some Layer 3 work, and is the main VLAN handler, so it handles VLANS 10, 11 and 12. Off of the 3560G is my server in VLAN 12, running DHCP for those devices.
Anytime I repower the PC in Building A, or try to release and renew the IP address, I get an IP address from 12. And it shows up on the 12 server. I want it to get an 11 IP, since it's in VLAN 11.
The port on the 3560 that has the 2950 attached:
interface FastEthernet0/14
description Connection Cisco 2950
switchport trunk encapsulation dot1q
switchport trunk native vlan 11
switchport mode trunk
The 2950 port connecting to the 3560 looks like this:
interface FastEthernet0/17
switchport trunk native vlan 11
switchport mode trunk
The port that my PC (off the 2950 is on) looks like this:
interface FastEthernet0/20
switchport access vlan 11
The 3560 port that connects to the 3560G:
interface GigabitEthernet0/1
description Connection to Main 3560G
switchport trunk encapsulation dot1q
switchport mode trunk
srr-queue bandwidth share 10 10 60 20
srr-queue bandwidth shape 10 0 0 0
queue-set 2
mls qos trust cos
auto qos voip trust
All devices on the 3560 properly get an 11 IP, so it must be something with my 2950.
NOW, here's something TOTALLY FLIPPIN WEIRD (if you ask me!) If I take that PC that's off the 2950, and give it a static 11 IP addy, with a proper subnet and default gateway and DNS...it cannot access the server or the web.
Totally stumped and would love a little guidance.
11-12-2009 01:00 PM
Hi.
Definitely sounds weird. Soemhow the VLAN11 of the 2950 seems to be swapped to VLAN12 of the rest of the network. IF the same VLAN11 from your 3560 was on the 2950 as well, your test with static IP should show connectivity.
Would it be possible to have the software versions and running config from all switches involved? It might be of help for us to give you guidance?
And "show vtp status" and "show vlan brief" from all switches as well?
HTH, Ingolf
11-13-2009 07:25 AM
11-13-2009 07:28 AM
11-13-2009 07:34 AM
11-13-2009 07:35 AM
11-13-2009 08:44 AM
I would say somewhere you have a connection that is bridged between 11 and 12 .There is no ip helper statement on the 3560G so in order to get an address from a device in vlan 12 it would have to bridged somewhere. Check cdp between the 2950 and 3560 and make sure its on the ports you think its on . A dhcp broadcast to a server in the same vlan should just be answered by that server , the fact that 12 is answering indicates somehow 11 and 12 are bridged because I see no ip helper statements on the "G" box. If you give it a static can you ping the 3560G vlan 11 interface and all the other layer 3 interfaces ok?
11-13-2009 10:52 AM
If I give the PC a static in the 11 range, 255.255.255.0 subnet, gw of .254 (just like the PCs hanging off the 3560 using DHCP get), I *cannot* ping the server on the 3560, nor the gw!!
I have another site with a similar setup, but there we hung a 3Com off the 3560. I know the 2950 is kind of an old box....but looks like my solution might be to retire the 2950 and use a 3Com. Not sure why...
Right now this setup works OK, but I have to go to PCs on this switch and hardcode their DNS to be the server in the 11 range or logins take forever.
If anyone can think of anything else, I would love to hear it.
11-13-2009 12:53 PM
Can you post from each switch
1) "sh int trunk"
2) "sh cdp neigh"
Jon
11-13-2009 03:03 PM
No reason the 2950 shouldn't work , something is not configured quite right. The trunk appears not to be working like it should. If you do a show cdp neighbor does it correspond to the ports you think it should be in the config on the 2950 and 3560 ? Also use cdp neighbor to see if you have connections where they shouldn't be such as bridged between a port in vlan 11 and a port in vlan 12 .
11-16-2009 07:56 AM
From the 3560 (mcphee)
sho int trunk
Port Mode Encapsulation Status Native vlan
Fa0/14 on 802.1q trunking 11
Fa0/24 on 802.1q trunking 1
Gi0/1 on 802.1q trunking 1
Port Vlans allowed on trunk
Fa0/14 1-4094
Fa0/24 1-4094
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Fa0/14 1,5-6,9-12
Fa0/24 1,5-6,9-12
Gi0/1 1,5-6,9-12
Port Vlans in spanning tree forwarding state and not pruned
Fa0/14 1,5-6,9-12
Fa0/24 1,5-6,9-12
Gi0/1 1,5-6,9-12
From the 3650
sho cdp neigh
(clipped)
2950 Fas 0/14 123 T S WS-C2950T-Fas 0/17
From the 2950
sho int trunk is not supported
From the 2950
show cdp neigh
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
MCPhee Fas 0/17 129 S I WS-C3560-2Fas 0/14
11-13-2009 03:13 PM
"switchport trunk encapsulation dot1q" needs to be set on both side of the link.
You've it set only in the 3560 for int fa0/14. Try adding the same command to the 2950 fa0/17.
11-13-2009 03:18 PM
You can't set it on the 2950 because the 2950 only supports 802.1q so there is no "switchport trunk encapsulation ..." command available on this switch.
Jon
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide