Task 1.4 - Why change the system mtu on the customer switch?

For this task we're required to create a dot1q tunnel between fa0/5 on SW1 and fa0/17 on SW4. SW2's fa0/20 is the customer port connecting to fa0/17 on SW4. So why does the SG configure SW2 (the customer switch) with an increased mtu?

Isn't the metro-tag removed by SW4 prior to sending the frame to SW2?

Also, in a previous mock lab I was penalised for not configuring 'vlan dot1q tag native' on the service provider switches, but the SG doesn't configure 'vlan dot1q tag native' for this task. Isn't it 'best practise' to implement native vlan tagging on the service provider switches?

Comments

  • Hi David,

    I agree with you; in this case SW2 does not need to have MTU adjusted, I am not sure why the SG adjusted it over there - maybe it is wrong?

    As for the dot1q tag native, that is indeed a best practice to improve security, however it is not necessary. I don't think you would loose any points by not putting it

    HTH

    Good luck!

  • Hi david,

    The system mtu 1504 is not needed on SW2 because it is the CPE switch. I believe it was just a typo-error on the SG. I did get the points for this task when I did mock lab 3 last march, I did not configure SW2 for "system mtu 1504".

    Also, in a previous mock lab I was penalised for not configuring 'vlan dot1q tag native' on the service provider switches, but the SG doesn't configure 'vlan dot1q tag native' for this task. Isn't it 'best practise' to implement native vlan tagging on the service provider switches?

    Yes it is best practice to configure vlan dot1q tag native on Service Provider Edge Switches so that all packets going out an IEEE 802.1Q trunk, including the native VLAN, are tagged. If the switch is configured to tag native VLAN packets on all IEEE 802.1Q trunks, the switch accepts untagged packets, but sends only tagged packets. You can add this command on SW1 and SW4 and you will not be penalized.

    It is explicitly stated in the Configuration task "If an additional VLAN is needed use VLAN 100". For this task, it is okay not to configure vlan dot1q tag native because the tunneling port is assigned to Access Vlan 100. Since VLAN 100 is not used as native vlan on SW1 or SW4 trunk ports, then there will be no problem. However, if VLAN 100 is used as native VLAN between SW1-fa0/21-fa0/15-SW4 trunk link, then you need to configure vlan dot1q tag native both on SW1 and SW4 so that traffic from Customer are tagged when sent to this trunk port.

    HTH,

    Carlos

  • For this task, it is okay not to configure vlan dot1q tag native because the tunneling port is assigned to Access Vlan 100. Since VLAN 100 is not used as native vlan on SW1 or SW4 trunk ports, then there will be no problem. However, if VLAN 100 is used as native VLAN between SW1-fa0/21-fa0/15-SW4 trunk link, then you need to configure vlan dot1q tag native both on SW1 and SW4 so that traffic from Customer are tagged when sent to this trunk port.

    Thanks - that's cleared it up for me.

  • I did get the points for this task when I did mock lab 3 last march, I did not configure SW2 for "system mtu 1504

    Since you've done Mock Lab 3 I'm going to assume you've done other Mock Labs?... How do you think Mock Lab 3 rates in terms of the apparent 7/10 difficulty that INE states it to be?

    I did Mock Lab #4 last week which is apparently 9/10 on the difficulty scale, I scored 70 for that and I found it 'easier' than Lab 3 which is meant to be 7/10... whats up with that?

    The wheels seem to be falling off as my lab day approaches.

     

  • Since you've done Mock Lab 3 I'm going to assume you've done other Mock Labs?... How do you think Mock Lab 3 rates in terms of the apparent 7/10 difficulty that INE states it to be?

    I did Mock Lab #4 last week which is apparently 9/10 on the difficulty scale, I scored 70 for that and I found it 'easier' than Lab 3 which is meant to be 7/10... whats up with that?

    The wheels seem to be falling off as my lab day approaches.

    I have done Mock lab 1,2 last February, Mock lab 3 last March. April was my first attempt. I will do the rest of the mock labs around June-July since July will be my 2nd attempt.

    Hmm, mock lab 3? I rate it as difficulty 7. I failed in mock lab 1,2 with score 74,75 respectively. Mock lab 3 was more difficult than mock lab 1&2 but I passed it with an exact score of 80. This gave me "enough" confidence for the real lab. I though it was enough but it wasnt. For the remaining mock labs (difficulty 8,9,10) I should be able to pass them on June/july.

    Hmm, you found mock lab 4 to be easier? Maybe the topics in mock lab 4 are your strengths? Or you were better when you took mock lab 4?

    With the wide blueprint of the Lab exam, difficulty level will depend on the strengths of the candidate. Target is to master every topic by assuming that the Lab exam can throw anything at us. Jeez.

     

    Good luck on your lab day! ; )

  • Thanks Carlos.

    I think that for me the exam will be less about the technology and more about reading and interpretting the question and not making small mistakes and oversights. I've done 4 mock labs now, and I'm not really finding that it's my technical knowledge that lets me down, it's small mistakes, oversights and mis-interpretation of questions.

    I'll give you an example, one of the spanning-tree tasks in Mock Lab 3 says, 'don't incease cost on any port to achieve this', so my thought process immediately moves to, 'don't touch spanning-tree cost', but the solution is looking for decreasing STP cost... it's plain as day in hindsight, but I keep missing small details like this when I'm under exam conditions... Even after 4 mock labs..

  • I'll give you an example, one of the spanning-tree tasks in Mock Lab 3 says, 'don't incease cost on any port to achieve this', so my thought process immediately moves to, 'don't touch spanning-tree cost', but the solution is looking for decreasing STP cost... it's plain as day in hindsight, but I keep missing small details like this when I'm under exam conditions... Even after 4 mock labs..

    Hahaha. What a coincidence. I got same wrong interpretation as you did for that Task1.6 of Mock lab3. I also thought of not changing spanning-tree cost. I skipped this task initially then when I got back, I still didn't notice the wording so I had no choice but to touch SW3.

    The devil is in the wording details. This is very true in the real lab. Is it your first attempt? When?

     

  • Glad to know that I wasn't the only one who left that task until later, (but still managed to get it wrong).

    Yes, it's my first attempt on Friday 1st June in Sydney.

    I don't expect to pass on my first attempt.

    I'm hopeful, but I've also got realistic expectations, even more so now.

  • Yes, it's my first attempt on Friday 1st June in Sydney.

    I don't expect to pass on my first attempt.

    I'm hopeful, but I've also got realistic expectations, even more so now.

    That's okay, just give your best shot. It's good that you are emotionally prepared for failure, it will give you less pressure on the lab day itself. 

    In my first attempt I was technically confident, positive mood, and emotionally prepared. So even if I failed, I wasn't shattered badly. I accepted and know that my technical knowledge and strategy are still not enough to pass the exam. Whatever Cisco does to this exam, it's totally up to us to achieve the necessary level to pass. 

    Best of luck. ; )

  • Hi David and Carlos,

    I'm only starting Workbook Vol. 1 however your words "don't touch spanning-tree cost', but the solution is looking for decreasing STP cost..." help a lot to pay attention to every single detail.

    Thanks for sharing and the best luck for you guys.

     

    Regards

    AC

     

     

     

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