One goal of last week’s question and this week’s question is to give you a better idea of the level of complexity of questions on the ICND1 exam versus the ICND2 exam. Today, I’ll take what was frankly a relatively simple example last week, and turn it into what may well be as tricky as a LAN-switch-forwarding question might get on the ICND2 exam.
Before you read today’s new question, let me ramble a bit about what I wrote below. I finally gave up trying to make this question an “exam realistic” question in all ways. The problem is that to give you a lot to think about (which was my primary goal), I’d need to give you far more info than a single exam question is likely to force you to read. On the exam, the kind of detail shown below might be seen in a simlet question, where you get to pick which commands to use, but it’s a lot more to read than I’ve ever seen on a CCNA-level multiple choice question. However, for the sake of discussion, I’ll pose it as a multiple choice question, and then give you enough output on the switches to find the answer. So, don’t sweat how much time it takes you – it’s not a realistic question for testing your speed. The more important part of this one is to give us something to practice/review/discuss.
That said, if you’re like me, and still want to gauge your speed, start you timers… now!
Question: A frame arrived at SW1, source MAC address 0200.1111.1111, destination MAC address 0200.BBBB.BBBB. All interfaces in the figure are up/up. No static MAC addresses have been configured, and port security also has not been configured. Which of the following are true?
A) SW1 will not forward the frame over any trunks
B) SW2 will receive (at least) 1 copy of the frame from SW1, but none from SW3
C) Both SW1 and SW2 will forward a copy of the frame towards SW3
D) The frame will loop
SW1#show mac address-table dynamic
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
1 000f.2343.87d9 DYNAMIC Gi0/2
1 0010.7b39.e9be DYNAMIC Gi0/2
1 0013.197b.6588 DYNAMIC Fa0/3
1 0060.5cf4.965d DYNAMIC Gi0/2
2 0200.1111.1111 DYNAMIC Fa0/1
2 0200.2222.2222 DYNAMIC Gi0/1
3 000f.2343.87d9 DYNAMIC Gi0/2
4 000f.2343.87d9 DYNAMIC Gi0/2
Total Mac Addresses for this criterion: 8
SW1#show interfaces trunk
Port Mode Encapsulation Status Native vlan
Fa0/8 on 802.1q trunking 1
Gi0/1 on 802.1q trunking 1
Gi0/2 on 802.1q trunking 1
Port Vlans allowed on trunk
Fa0/8 1-4094
Gi0/1 1-4094
Gi0/2 1-4094
Port Vlans allowed and active in management domain
Fa0/8 1-4
Gi0/1 1-4
Gi0/2 1-4
Port Vlans in spanning tree forwarding state and not pruned
Fa0/8 2
Gi0/1 2
Gi0/2 1-4
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! SW2 next
SW2#show mac address-table dynamic
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
2 0019.e86a.6f99 DYNAMIC Gi0/2
2 0200.2222.2222 DYNAMIC Fa0/2
1 000f.2343.87da DYNAMIC Gi0/1
1 0010.7b39.e9be DYNAMIC Gi0/1
1 0013.197b.2f59 DYNAMIC Fa0/14
1 0013.197b.6588 DYNAMIC Gi0/1
1 0019.e86a.6f88 DYNAMIC Fa0/9
1 0019.e86a.6f99 DYNAMIC Gi0/2
1 0060.5cf4.965d DYNAMIC Gi0/1
3 000f.2343.87da DYNAMIC Gi0/1
4 000f.2343.87da DYNAMIC Gi0/1
Total Mac Addresses for this criterion: 11
SW2#show interfaces trunk
Port Mode Encapsulation Status Native vlan
Fa0/9 auto 802.1q trunking 1
Gi0/1 auto 802.1q trunking 1
Gi0/2 auto 802.1q trunking 1
Port Vlans allowed on trunk
Fa0/9 1-4094
Gi0/1 1-4094
Gi0/2 1-4094
Port Vlans allowed and active in management domain
Fa0/9 1-4
Gi0/1 1-4
Gi0/2 1-4
Port Vlans in spanning tree forwarding state and not pruned
Fa0/9 1,3-4
Gi0/1 1-4
Gi0/2 1-4
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
! SW3 next
SW3#show mac address-table dynamic
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
1 0010.7b39.e9be DYNAMIC Fa0/22
1 0013.197b.2f59 DYNAMIC Gi0/2
1 0013.197b.6588 DYNAMIC Gi0/1
1 0019.e859.5399 DYNAMIC Gi0/2
1 0019.e86a.6f9a DYNAMIC Gi0/1
1 0060.5cf4.965d DYNAMIC Fa0/21
2 0019.e86a.6f9a DYNAMIC Gi0/1
2 0200.1111.1111 DYNAMIC Gi0/1
2 0200.2222.2222 DYNAMIC Gi0/1
2 0200.bbbb.bbbb DYNAMIC Fa0/2
Total Mac Addresses for this criterion: 10
SW3#show interfaces trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Gi0/2 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Gi0/2 1,3-4094
Port Vlans allowed and active in management domain
Gi0/1 1-4
Gi0/2 1,3-4
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1-4
Gi0/2 1,3-4
So, enjoy pondering this one for a bit. Feel free to post ideas; for those of you wanting to work on it solo, just try and ignore any other posts from other readers until you’re happy with your answer. Next posting, I’ll start working through it, and give a few hints.
