1

so for simplicity sake in testing this configuration, I have a sample project that looked like this: enter image description here breakdown:

Configurations

vlans configured on multilayer switch which is also vtp server:

vlan 2:

ip address 192.168.2.1 255.255.255.0

ip helper-address 192.168.3.1

vlan 3:

  • ip address 192.168.3.2 255.255.255.0

dhcp resides in vlan 3, static address 192.168.3.1

pool:

  • default gateway: 192.168.3.254

  • starting ip: 192.168.3.2

  • subnet mask: 255.255.255.0

  • maximum users: 200

all crossover connections are trunks (verified)

all straight connections are assigned to vlan 3 (verified)

pc 1 & 2 can properly receive a response from the DHCP server, but PC0 cannot.

I'm trying to get this to work while attempting to debug a 3 tier network design I'm working on for my networking 101 class. After multiple days trying to figure out why the traffic is not properly routing, I broke down the design trying to find the point of failure. As far as I have narrowed down, the issue is from intermediary switch (switch 1) which is part of the distribution layer but I am unable to grasp what is wrong with it's configuration (all ports trunk, vtp mode transparent).

I feel like I've missed something very fundamental in the routing setup, especially as I've gotten this configuration to work in the past, but I am unable to replicate the proper configuration.

//
//multilayer switch0
//
Building configuration...

Current configuration : 2249 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
!
!
ip routing
!
!
!
!
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface FastEthernet0/1
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/2
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/3
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/4
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/5
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/6
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/7
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/8
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/9
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/10
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/11
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/12
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/13
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/14
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/15
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/16
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/17
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/18
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/19
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/20
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/21
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/22
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/23
 switchport trunk encapsulation dot1q
!
interface FastEthernet0/24
 switchport trunk encapsulation dot1q
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
interface Vlan2
 mac-address 0010.1151.c701
 ip address 192.168.2.1 255.255.255.0
 ip helper-address 192.168.3.1
!
interface Vlan3
 mac-address 0010.1151.c702
 ip address 192.168.3.254 255.255.255.0
!
ip classless
!
ip flow-export version 9
!
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end


//
//switch 0
//
Switch#sh running-config
Building configuration...

Current configuration : 2168 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
spanning-tree mode pvst
!
interface FastEthernet0/1
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/2
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/3
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/4
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/5
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/6
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/7
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/8
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/9
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/10
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/11
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/12
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/13
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/14
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/15
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/16
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/17
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/18
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/19
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/20
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/21
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/22
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/23
!
interface FastEthernet0/24
 switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
end

//
//switch1
//
Building configuration...

Current configuration : 1620 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
vtp mode transparent
!
!
spanning-tree mode pvst
!
interface FastEthernet0/1
 switchport mode trunk
!
interface FastEthernet0/2
 switchport mode trunk
!
interface FastEthernet0/3
 switchport mode trunk
!
interface FastEthernet0/4
 switchport mode trunk
!
interface FastEthernet0/5
 switchport mode trunk
!
interface FastEthernet0/6
 switchport mode trunk
!
interface FastEthernet0/7
 switchport mode trunk
!
interface FastEthernet0/8
 switchport mode trunk
!
interface FastEthernet0/9
 switchport mode trunk
!
interface FastEthernet0/10
 switchport mode trunk
!
interface FastEthernet0/11
 switchport mode trunk
!
interface FastEthernet0/12
 switchport mode trunk
!
interface FastEthernet0/13
 switchport mode trunk
!
interface FastEthernet0/14
 switchport mode trunk
!
interface FastEthernet0/15
 switchport mode trunk
!
interface FastEthernet0/16
 switchport mode trunk
!
interface FastEthernet0/17
 switchport mode trunk
!
interface FastEthernet0/18
 switchport mode trunk
!
interface FastEthernet0/19
 switchport mode trunk
!
interface FastEthernet0/20
 switchport mode trunk
!
interface FastEthernet0/21
 switchport mode trunk
!
interface FastEthernet0/22
 switchport mode trunk
!
interface FastEthernet0/23
 switchport mode trunk
!
interface FastEthernet0/24
 switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
end

//
// switch 2
//
Building configuration...

Current configuration : 2168 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
spanning-tree mode pvst
!
interface FastEthernet0/1
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/2
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/3
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/4
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/5
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/6
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/7
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/8
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/9
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/10
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/11
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/12
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/13
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/14
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/15
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/16
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/17
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/18
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/19
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/20
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/21
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/22
 switchport access vlan 2
 switchport mode access
!
interface FastEthernet0/23
!
interface FastEthernet0/24
 switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
end

//
// switch 3
//
Building configuration...

Current configuration : 1118 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
!
!
!
spanning-tree mode pvst
!
interface FastEthernet0/1
 switchport access vlan 3
 switchport mode access
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
 switchport mode trunk
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
end
0

You either need to use VTP or manually configure the VLANs in global configuration, and you can optionally name them so that it makes sense:

Vlan 2
 name Name2
!
Vlan3
 name Name3
!
| improve this answer | |
  • sorry those configs are from me trying literally anything to debug the routing problems, unfortunately even fixing them does not fix the issue (I've fixed the vlan 3 svi to point to 192.168.3.254 (I believe it "should" correspond with the the default gateway in the DHCP pool). there is no change. vlan 2 does have a pool but it doesn't seem relevant considering all the problem PC's are on vlan 3 (not touching inter-vlan routing until I have this sorted). – user2835725 Jan 9 '17 at 4:13
  • You need to give us the configurations you were thinking should work. By the way, I don't see where you have defined the VLANs on the switches, e.g. Vlan 3 in global configuration. Since you have VTP in transparent mode, you need to define the VLANs. – Ron Maupin Jan 9 '17 at 4:17
  • I believe all those issues are fixed by changing "int vlan 3" ip address 192.168.3.254 255.255.255.0, I've updated the configurations to reflect that. as to the switches, only switch 1 is transparent, I was under the impression that intermediary switches do not need to know about the Vlans as trunked frames are not detagged/retagged. (just tested this, and setting the vtp mode to client and verifying that the vlans sync'd properly does not fix the issue). appreciate your willingness to help – user2835725 Jan 9 '17 at 4:23
  • Did you try configuring the VLANs on the switches? – Ron Maupin Jan 9 '17 at 4:27
  • I stand corrected: after a few minutes with the new configuration, the frames started successfully passing through the intermediare switch (switch 1) and pc 0 is now properly communicating with the DHCP. I guess I was ill informed that intermediary switches could be transparent. thank you very much for your help – user2835725 Jan 9 '17 at 4:28

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