CCNP HELP!

[yasin.zahid]

Hi All,

I am studding for my Cisco Switch exam and I have created a small network using packet tracer. I think there is something wrong with my config as I see some link I expect to be blocked and they are fowarding. I have attached the packet tracer file you someone could have a look and just let me know where i am going wrong and maybe even what more I could include to my network.

Thanks,

[Peter Paluch]

Hello,

I can have a look on your PT file. However, I have to point out that while the PT is a great teaching tool, it is only limited to basic CCNA and CCNA Security functionality. CCNP topics cannot be mastered in PT and there are even issues related to more complicated network designs that PT is unable to simulate properly. The STP is one of those protocols which are not correctly simulated in PT, and there are indeed situations where the PT allows a port to be in forwarding state while with real STP implementation, the port should be blocked.

So in fact, your configuration is probably correct, just the PT is having problems simulating the network properly.

PT is not intended and not suitable for CCNP-related activities.

Best regards,

Peter

[yasin.zahid]

Hi,

Thank for your reply, I know its not for CCNP but I am only trying a few thing from CCNP on Packet Tracer witch I know work like MLS, Syslog, etherchannal ect. I would much appreciate it if you had a look and let me know what missing or what I have done wrong.

Also thanks for the info about STP issues in Packet Tracer that may well be the problem.

Regards,

[Peter Paluch]

Hello,

Allright, I will have a look in a few upcoming hours. Can you be more specific about the problem you are trying to solve? What exactly do you believe is wrong and on what switch does the problem occur? Be as specific as possible. Thank you!

Best regards,

Peter

[yasin.zahid]

Hi,

I have a network with 4 switches and 5 Vlans (Excluding vlan 1) I have a distribution/core  layer which has 2 3560 switches one of which is routing the vlans (Root_Switch). The 2 3560 switches are connected together by 2 cables that are configured with a channel-grope 1 using the channel-protocol lacp (Link aggression control protocol (Gi0/1 - 2).  The Switch (Root_Switch) is the root switch for all vlans and the switch (Back_up) is the back or secondary root switch for rapid spanning tree.

There are 2 more switches which are access layer switches. They are configured in a similar way as they have an etherchannel grope (2) (fa0/22 – 23) between them. As switch0 is directly connected to Root_switch the port it is connected with should be a root port (port fa0/24) and therefor the port channel (interface portchannel 2) should be blocked. I see one of the ports blocked (fa0/23) the other one still forwarding (fa0/22) even though these port are meant to be in a port channel and it should show po2 as block. Switch0 has a priority of 36864 which is higher than all switches.

The native vlan is vlan 50. The IP scheme is 192.168.x.0 /24 where x is the vlan number. Laptops are in the sales vlan and desktops are in the engineering vlan.

I am not sure if it’s something to do with the port channel being misconfigured or it’s something to do with spanning tree. I have a list of objectives I wanted to complete. That should give you an idea of what I have already done. I belive the problem is on switch0 or on the other access layer switch. (I have not put the command ip default-gateway 192.168.50.1 in for the access layer switches.)

I hope this is detailed enough for you.

Thank you

zahid

[Peter Paluch]

Hello Zahid,

I did not find anything wrong with your configuration. In fact, on SW1, the ports Fa0/22 and Fa0/23 were reported as I-ports (i.e. unbundled) in the show etherchannel summary command output while on SW2, they were at the same time reported as P-ports (bundled in Etherchannel). Such a situation would never occur on real devices. This seems like a PT bug - wrong modelling of the Etherchannel signalization and buildup.

The topology began behaving more stable when I changed the Etherchannel mode on SW2 from passive to active. After this change, the Etherchannel came up again and did not decompose into its member links. The STP then showed the Po2 interface on SW1 as Alternate Discarding which was indeed appropriate for your network.

Furthermore, the command show spanning-tree interface port-channel 2 produced an output that no STP information is available for that port. That is another bug - the Po2 was an interface displayed in show spanning-tree output together with its states. It is impossible that no STP info was present.

My original assumption is hereby confirmed - the PT does not properly simulate the processes about Etherchannel and STP.

Best regards,

Peter

[yasin.zahid]

Hi Peter,

Thank you for you help. I passed my Cisco Switch exam today

regards,

Zahid

[Somasundaram Jayaraman]

Congrats Zahid