2960 - Trunking Issue

[joseluis]

Hi,

I have an issue on Cisco 2960 Switch I don't know if this is an issue or I just forget some configurations

Scenario Topology:

:

DHCP Configuration on Router:

ip dhcp pool VLAN5
network 5.5.5.0 255.255.255.0
default-router 5.5.5.254

interface FastEthernet0/0.5
encapsulation dot1Q 5
ip address 5.5.5.254 255.255.255.0

Done Configuration:

1. Configured DHCP Router to Subinterface fa0/0.5, IP Address of the sub-interface is 5.5.5.254/24

2. Configured Management IP VLAN 1 of the SW as 5.5.5.5/24

3. Configured Switch Facing the DHCP Router to Trunk, also added VLAN 5 to the switch

4. Configured SW port 2 to access VLAN 5 facing the terminal

5. Configured default-gateway on SW to 5.5.5.254

In my own understanding on this set-up terminal should able to obtain IP address provided by the DHCP, right?

Problems Encountered:

1. Router cannot ping management of switch (5.5.5.5) vice versa

2. Terminal cannot obtain IP address from DHCP Router, but when I tried to static the terminal I can ping the gateway 5.5.5.254, which is the router interface?

I.find it weird because, Terminal can ping the router interface (Gateway) but from switch, cannot ping the router interface?

What seems to be the problem?

Thank you so much!

[Georg Pauwen]

Hello,

at first glance, I would say the problem is that both Vlan 1 and Vlan 5 share the same address space.

This looks like a Packet Tracer file, can you post the project (zip it first, otherwise you cannot upload) ?

[joseluis]

Hi Georg,

Thank you for your reply, actually I am simulating this using real cisco equipment, I am just simulating something. I'll just post here the necessary configs.

Router Config:

ip dhcp pool VLAN5
network 5.5.5.0 255.255.255.0
default-router 5.5.5.254
dns-server 4.4.4.2
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.5
encapsulation dot1Q 5

description Link-to-Switch
ip address 5.5.5.254 255.255.255.0

Switch Config:

interface GigabitEthernet1/0/1
description Connection to PC
switchport access vlan 5
switchport mode access

interface GigabitEthernet1/0/24
description Link-to-Router
switchport mode trunk

interface Vlan1
ip address 5.5.5.5 255.255.255.0
!
ip default-gateway 5.5.5.254

Is this okay with you now?

Thank you!

[Georg Pauwen · Accepted solution]

Hello,

the router cannot ping the management interface of the switch because it is in the same address space. If you do a 'show ip route' on the router, you will see network 5.5.5.0/24 as connected, which means the router sees that network as local. The solution would be to use a different address space for VLAN 1 (e.g. 1.1.1.0/24).

As for the terminal not getting a DHCP address, try configuring 'spanning-tree portfast' on GigabitEthernet0/1/0.