Refer to the exhibit. Switch#show etherchannel summary

Double-Tagging attack:
In this attack, the attacking computer generates frames with two 802.1Q tags. The first tag 
matches the native VLAN of the trunk port (VLAN 10 in this case), and the second matches the 
VLAN of a host it wants to attack (VLAN 20). 
When the packet from the attacker reaches Switch A, Switch A only sees the first VLAN 10 and 
it matches with its native VLAN 10 so this VLAN tag is removed. Switch A forwards the frame 
out all links with the same native VLAN 10. Switch B receives the frame with an tag of VLAN 
20 so it removes this tag and forwards out to the Victim computer. 
Note: This attack only works if the trunk (between two switches) has the same native VLAN as 
the attacker. In other words, this attack is only successful if the attacker belongs to the native 
VLAN of the trunk link. Another important point is, this attack is strictly one way as it is 
impossible to encapsulate the return packet. 
To mitigate this type of attack, we can use VLAN access control lists (VACLs, which applies to 
all traffic within a VLAN. We can use VACL to drop attacker traffic to specific victims/servers); 
or implement Private VLANs; or keep the native VLAN of all trunk ports different from user 
VLANs. 
Question 104
Refer to the exhibit. 
R1#show ip route 
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP 
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 

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E1 - OSPF external type 1, E2 - OSPF external type 2 
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 
ia - IS-IS inter area, * - candidate default, U - per-user static 
route 
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP 
+ - replicated route, % - next hop override 
Gateway of last resort is 10.56.0.1 to network 0.0.0.0 
S* 
0.0.0.0/0 [1/0] via 10.56.0.1 
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 
C 
10.56.0.0/17 is directly connected, Vlan56 
L 
10.56.0.19/32 is directly connected, Vlan56 
C 
10.56.128.0/18 is directly connected, Vlan57 
L 
10.56.128.19/32 i directly connected, Vlan57 
When router R1 is sending traffic to IP address 10.56.192.1, which interface or next hop address 
does it use to route the packet? 
A. 0.0.0.0/0 
B. Vlan57 
C. 10.56.0.1 
D. 10.56.128.19