Lab error - Duplicate address scrolling

Tricon7

I'm fooling around with the hands-on sheet now. Perhaps someone can answer a question, since no one in the lab has had any Cisco classes.

I don't know if the setup of the network should be setup in a specific sequence, equipment-wise, but I started with the switches. I configured one host on switch A with the same default gateway as the host on switch B. The IP of host 1 is the same as VLAN 1 on switch A - 192.168.1.2. The IP of host 2 is the same as VLAN 1 on switch B - 192.168.1.3. I was getting dup MAC address errors on VLAN 1 on both hosts/switches. Now I'm confused; I think I'm setting this up wrong somehow in a basic way. The IP addresses of each host should be different. What about the VLAN 1 IP address on each switch? Are they the same or different? However, I thought the host IP should match the VLAN 1 IP. If so, then that's what I did and I'm getting the "DUPADDR: Duplicate address 192.168.1.2 on Vlan1, sourced by xxxxxx" error on both switches, even after I change the VLAN IP on one.

Got any ideas? Should I have configured something else first?

widjerd

Vlan 1 should be regarded as a host address, IE must be unique as it is what you telnet into to manage the switch from hosts.

You cannot duplicate IP addresses anywhere and all they need is to be in the same subnet

Host1

---

Switch1 VLAN1

---

Switch2 VLAN1

---

Host2
192.168.0.1

---

192.168.0.2

---

192.168.0.3

---

192.168.0.4

Paul Boz

Set up your vlans and trunk them via a router before you worry about switching. Do you have any routers in your lab? What's your overall lab topology for this lab?

Netstudent

nah, I wouldn;t give your hosts the same IP as your Interface Vlan1 IP. Even though Interface vlan 1 is a virtual interface, it is still a logical address, and therefore cannot be duplicated. Just give your hosts another IP in the same subnet as the VLAN1 interfaces.

Tricon7

Paul Boz wrote:

Set up your vlans and trunk them via a router before you worry about switching. Do you have any routers in your lab? What's your overall lab topology for this lab?

That was another issue picking at my brain - which part to setup first. Ok, I have three routers and two switches. My first router is my ISP; Router2 connects to it and to Router3. Router3 connects to Switch1, which connects in turn to Switch1. For this lab I have two hosts connected to Switch1 and one host connected to Switch2.

I'm basically doing it all for this exercise: creating/naming VLANs, trunking switch-to-switch via 802.1Q and to a router, setting up a VTP domain with a client/server, using STP and forcing a switch to be root bridge. Portfast and port security, also, natch.

So I should configure the routers before I worry about configuring the switches, then? Reverse order would give me problems? Also, I'm supposed to use 802.1Q trunking for the switches to communicate with each other. However, one of them is a 2550 and the other is only a 2900. Is that going to pose a problem?

Netstudent

Like Paul said, start with layer 3 first and then move on to layer 2. Setup the router interfaces/subinterfaces with the IP scheme you want, along with the trunk encapsulation, and the vlan ID for each interface.

Also remember the cisco way says to put the native vlan on a physical interface with the "Native" keyword. encapsulation dot1q 1 native..

Then begin with your VTP domain, VLAN 1 interface IP's, default-gateway, VLAN creation and trunk ports.

Then I would start assigning VLAN access ports.

Thats how I do it and I can get it everytime now.


If the 2550 has dot1q capabilities, then no i don't think it would cause a problem.I'm not 100% positive on that though. 802.1Q is an open standard with added interoperability as opposed to ISL.

Tricon7

Netstudent wrote:

Like Paul said, start with layer 3 first and then move on to layer 2. Setup the router interfaces/subinterfaces with the IP scheme you want, along with the trunk encapsulation, and the vlan ID for each interface.

Also remember the cisco way says to put the native vlan on a physical interface with the "Native" keyword. encapsulation dot1q 1 native..

Then begin with your VTP domain, VLAN 1 interface IP's, default-gateway, VLAN creation and trunk ports.

Then I would start assigning VLAN access ports.

Thats how I do it and I can get it everytime now.


If the 2550 has dot1q capabilities, then no i don't think it would cause a problem.I'm not 100% positive on that though. 802.1Q is an open standard with added interoperability as opposed to ISL.

Sounds like a good plan. I'll give it a shot. In the meantime, my router that's connected to my switch won't "take" the encapsulation command. Here's what I put:

router(config)#int fa 0/0
router(config-if)#no shut
router(config-if)#int fa 0/0.1
router(config-subif)#encapsulation dot1q 1

At this point I got the error % Unrecognized command with the "^" symbol underneath the "e" in encapsulation. I tried all kinds of permutations with no success. I even put just a "?" at the (config-subif)# to see what my options were, but nothing showed for "encapsulation." My IOS is 12.2 and my router is a 2600.

Any help?

tech-airman

Tricon7 wrote:

Netstudent wrote:

Like Paul said, start with layer 3 first and then move on to layer 2. Setup the router interfaces/subinterfaces with the IP scheme you want, along with the trunk encapsulation, and the vlan ID for each interface.

Also remember the cisco way says to put the native vlan on a physical interface with the "Native" keyword. encapsulation dot1q 1 native..

Then begin with your VTP domain, VLAN 1 interface IP's, default-gateway, VLAN creation and trunk ports.

Then I would start assigning VLAN access ports.

Thats how I do it and I can get it everytime now.


If the 2550 has dot1q capabilities, then no i don't think it would cause a problem.I'm not 100% positive on that though. 802.1Q is an open standard with added interoperability as opposed to ISL.

Sounds like a good plan. I'll give it a shot. In the meantime, my router that's connected to my switch won't "take" the encapsulation command. Here's what I put:

router(config)#int fa 0/0
router(config-if)#no shut
router(config-if)#int fa 0/0.1
router(config-subif)#encapsulation dot1q 1

At this point I got the error % Unrecognized command with the "^" symbol underneath the "e" in encapsulation. I tried all kinds of permutations with no success. I even put just a "?" at the (config-subif)# to see what my options were, but nothing showed for "encapsulation." My IOS is 12.2 and my router is a 2600.

Any help?

Tricon7,

Questions:

1. Which specific IOS version do you have?
2. Which specific "2600 series" router model do you have?

Paul Boz

Pretty odd that it will not let you set the encapsulation...