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Why can't I ping vlan 1 on my layer 3 switch

Posted on 2010-09-17
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Last Modified: 2012-08-13
I have a Cisco 3750 switch with vlan 1 ip address 10.0.0.55 that I cannot access from my desktop. I also have another Cisco 2960 switch with vlan 1 ip address of 10.0.0.54. I can access the 2960 but I cant access the 3750. But for me to access the 2960 from my desk it must go threw the link connected to the 3750. See diagram attached. Any help would be appreciated.
vlan1.doc
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Question by:AAMC
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Expert Comment

by:xzatech
ID: 33700985
do a no shut on the vlan int and also add a route ? gateway???
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Expert Comment

by:woolnoir
ID: 33701015
What Vlan is the PC on, what address range, what is the DefGW on your network specifically is it one of the switches that does the layer 3 routing or a seperate device. Is there any reason that the link between 10.0.0.4 and 10.0.0.55 isnt a dot1q trunk...
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Author Comment

by:AAMC
ID: 33701088
The pc is on another vlan, and I was  using vlan one to manage these switches. I'm just confused as to why I can get to one switch 10.0.0.54 and not 10.0.0.55 and my traffic has to go threw .55 to get to .54.
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Expert Comment

by:woolnoir
ID: 33701125
What device is your Gateway, and when you try to ping the VLAN 1 devices, do you put your switch access port in VLAN1 ?
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Expert Comment

by:woolnoir
ID: 33701163
Remember there is a difference between the physical and logical paths. The switches are connected with layer 2 connections , when your pinging you are using a layer 3 protocol, meaning that there needs to be a valid path between the SRC and DST device -  thats what we need to determine.

So... what VLAN was the PC when you tried the ping. Whats your default GW for the PC (when it  was being used as a test) and what physical device does your routing (is it one of the switches enabled for layer 3 routing).
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Author Comment

by:AAMC
ID: 33701212
The pc is in another vlan call vlan 72 that can see vlan 1. The default gateway for the PC is  the hsrp address of VLan 72. The device that has routing turn on is the device that I cannot ping which is the 3750 device ip's 10.0.0.55. I have no problem ping the other two devices vlan 1 interfaces.
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Expert Comment

by:woolnoir
ID: 33701289
Ok, so the default gateway for VLAN72 to which the PC is connected is a address belonging to the switch (10.0.0.55) can you ping the GW address of VLAN72 from the PC ? if yes, then we have identified the issue is localised to the switch.

Also, can you ping the PC from the switch?
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Author Comment

by:AAMC
ID: 33701412
Yes I can ping vlan 72's gateway from my pc. I can also ping my pc from the switch that my pc is plugged into. Vlan 72 also lives on the switch that my pc is connected to, it does not live on the switch with Vlan 1 interface ip 10.0.0.55. I cannot ping my pc from switch whose interface vlan 1 is 10.0.0.55.
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Expert Comment

by:woolnoir
ID: 33701465
Ok that doesnt make sense. If VLAN 72 doesnt live on the switch (10.0.0.55) then how can the gateway address for VLAN 72 be on that switch ?

You have access ports between the PC and SWITCH1, and between SWITCH1 and the 10.0.0.55 switch, what vlan is the access port between 10.0.0.4 and 10.0.0.55 ?

I can see why your having problems, can you maybe paste the config for 10.0.0.55 i'd be interested to see how you have it setup to allow it to function as the DEFAULTGW for vlan 72, and yet not have VLAN 72 on it ?
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Author Comment

by:AAMC
ID: 33701618
Switch 10.0.0.55
interface FastEthernet1/0/23 - IS WHERE I  connect the switch to Vlan 1 0f 10.0.0.4 int fa2/0/15 below

interface FastEthernet1/0/24  - this is one side of the trunk going threw comcast
 description Comcast HandOff
 switchport trunk encapsulation dot1q
 switchport mode trunk
!
interface GigabitEthernet1/0/1
!
interface GigabitEthernet1/0/2
!
**********THIS ENDS THE CONFIG FOR THE 1ST 3750*************************
Switch 10.0.0.4

interface Vlan1
 ip address 10.0.0.55 255.255.255.0
 no ip route-cache cef

interface FastEthernet2/0/15
 no snmp trap link-status
interface Vlan1
 ip address 10.0.0.4 255.255.255.0
 no ip route-cache
 no ip mroute-cache

**********THIS ENDS THE CONFIG FOR THE 2nd 3750*************************
Switch 10.0.0.54


interface FastEthernet0/24       this is the other end of the trunk comming from comcast
 description Comcast Handoff
 switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 description Management
 ip address 10.0.0.54 255.255.255.0
 no ip route-cache
0
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Author Comment

by:AAMC
ID: 33701732
Switch 10.0.0.55
interface FastEthernet1/0/23 - IS WHERE I  connect the switch to Vlan 1 0f 10.0.0.4 int fa2/0/15 below

interface FastEthernet1/0/24  - this is one side of the trunk going threw comcast
 description Comcast HandOff
 switchport trunk encapsulation dot1q
 switchport mode trunk
!
interface GigabitEthernet1/0/1
!
interface GigabitEthernet1/0/2
!
interface Vlan1
 ip address 10.0.0.55 255.255.255.0
 no ip route-cache cef
**********THIS ENDS THE CONFIG FOR THE 1ST 3750*************************
switch 10.0.0.4
interface FastEthernet2/0/15
 no snmp trap link-status
interface Vlan1
 ip address 10.0.0.4 255.255.255.0
 no ip route-cache
 no ip mroute-cache

**********THIS ENDS THE CONFIG FOR THE 2nd 3750*************************
Switch 10.0.0.54 - Cisco 2960 Layer 2


interface FastEthernet0/24       this is the other end of the trunk comming from comcast
 description Comcast Handoff
 switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 description Management
 ip address 10.0.0.54 255.255.255.0
 no ip route-cache
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Expert Comment

by:woolnoir
ID: 33701737
Can you show the whole config for 10.0.0.55 ? I dont see any VLAN definitions, nor any routing configuration. The issue is , without VLAN 72 being defined on 10.0.0.55 then your always going to have issues pinging outside vlan boundaries, its hard to tell why you can ping the device at the other end of the MPLS without seeing the full config for 10.0.0.55

There is a dot1q trunk between 10.0.0.55 and 10.0.0.54 meaning cross vlan traffic should be fine there, i presume your suing VTP to advertise the VLAN info, or is it manually done ?

The fact you only have a access port between 10.0.0.4 and 10.0.0.55 is odd .. i cant understand why, there is no downside to making it a dot1q trunk.

TO assist more i need more, ideally ALL of the 10.0.0.55 config.
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Author Comment

by:AAMC
ID: 33701790
That is basically all of the config, the only thing left is the passwords and the ip routing statement.  Nothing else is configure on this box. Thanks for all of your help
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Expert Comment

by:woolnoir
ID: 33701831
Thats the problem them, your pinging the VLAN 1 address on the switch, for that to work the packets have to go to the default GW which is in VLAN72 and then have a way of getting to VLAN1 - since the switch doesnt have any VLAN72 config on it, im not sure how it will deal with packets arriving tagged to VLAN 72.

can you do a

show ip route

on 10.0.0.55 and paste the output ?
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Expert Comment

by:woolnoir
ID: 33701841
Can you confirm the ACTUAL IP for the default GW on the PC, just tell me the IP, that might help ( i know you have mentioned it above, but i want to confirm the actual IP defined on the PC).
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Author Comment

by:AAMC
ID: 33701919
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set
     10.0.0.0/24 is subnetted, 1 subnets
C       10.0.0.0 is directly connected, Vlan1
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Author Comment

by:AAMC
ID: 33701997
I believe the problem is because I don't have a gateway of last resort configured
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Accepted Solution

by:
woolnoir earned 500 total points
ID: 33702325
So essentially the packets are arriving at that switch tagged as VLAN72 - coming from the VLAN72 subnet. The subnet mask will indicate that VLAN1 is different and thus packets need to go through a gateway and one doesnt exist.

To do this properly you need dot1q trunks between ALL switches, configure the VLANS on all switches, or use VTP to do this automatically. If the 10.0.0.55 switch had a definition for VLAN72 and VLAN1 the switch would have a route set automatically as the subnets (VLANS) would be directly connected.

How do you want me to go on from here, i can assist with how it SHOULD be setup as per best practise, but that could involve a fair bit of configuration - im happy to do this, but you need to make changes too ?
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Author Comment

by:AAMC
ID: 33703074
Thanks, I will make the changes as we proceed. Again,  thanks for all your patients and input
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Expert Comment

by:woolnoir
ID: 33703165
Ok looking at your switch configs i can see any mention of VLAN 72 - you have one range configured which is 10.0.0.0/24  according to the routing table. Before we start changing anything i need to be 100% sure how the network is configured. Can you start by giving me the info on which vlans you 'think' you have, what IP ranges they have, their subnet masks and the default gatways and the rough number of devices you have in them.

I.e

VLAN72 X.X.X.X subnet 255.255.X.X (or whatever is it ) Gateway=X.X.X.X number of devices = 10

Also can you tell me how the other ports on the switch are configured, are they all in VLAN72, is that your normal DATA vlan ?
also, do a ipconfig /all on the PC, and show me the output, i need the current IP, the subnet mask and the default Gateway.

That should start us off :)
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