04-23-2010, 07:32 AM
Could someone possibly explain the purpose of QID:BCM300?
Better yet, if someone could 'un-stupid' me as to why the explanation makes any sense that would be very cool. However, I would be astounded if anyone has actually 'done' this scenario and could demonstrate results aligning with the question, solution and explanation.
Intuitively the solution seems incorrect, but I went ahead and 'did' this one in a lab (several times actually on both real gear and GNS3) to just to see the problem first hand. Just take a look at the host on Vlan3 (10.1.3.2/24) - why in the world would RT1 accept a packet on its SVI that does not match the prefix for that (ingress) interface (let alone a network address which does not exist locally at all)? This is the result of ARP debugging on RT1 in the lab when the host on Vlan 3 tries to leave the subnet:
RT1#debug arp
ARP packet debugging is on
RT1#
Mar 18 08:16:25.557: IP ARP req filtered src 10.1.3.2 c421.0bb4.0000, dst 10.1.3.1 0000.0000.0000 wrong cable, interface Vlan3
RT1#
Mar 18 08:16:27.561: IP ARP req filtered src 10.1.3.2 c421.0bb4.0000, dst 10.1.3.1 0000.0000.0000 wrong cable, interface Vlan3
RT1#
Mar 18 08:16:29.549: IP ARP req filtered src 10.1.3.2 c421.0bb4.0000, dst 10.1.3.1 0000.0000.0000 wrong cable, interface Vlan3
RT1#
The output 'wrong cable' does not strike me as particularly encouraging. Meanwhile, arp debugging on the router acting as host3 shows that it has no way to map its configured gateway IP to a link MAC address (dst 10.1.3.1 0000.0000.0000 FastEthernet0/0) - you can see the 2 second 'throttled' delay interval between retransmissions in the debugging timestamps:
host3#debug arp
ARP packet debugging is on
host3#ping 200.1.1.2 rep 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 200.1.1.2, timeout is 2 seconds:
.Mar 18 08:16:25.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
.Mar 18 08:16:26.565: IP ARP throttled out the ARP Request for 10.1.3.1
.Mar 18 08:16:27.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
.Mar 18 08:16:28.565: IP ARP throttled out the ARP Request for 10.1.3.1
.Mar 18 08:16:28.565: IP ARP throttled out the ARP Request for 10.1.3.1
.Mar 18 08:16:29.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
.Mar 18 08:16:30.565: IP ARP throttled out the ARP Request for 10.1.3.1.
Success rate is 0 percent (0/1)
host3#
.Mar 18 08:16:31.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
host3#
Suffice it to say, the host on vlan 2 also has a gateway mismatch as well.
Information relevant to the question is supplied below. The url to the lab PDF documenting this scenario (qidbcm300.pdf), I think, demonstrates that the solution and explanation for this do not make sense. Again, if someone could point out something I'm overlooking that would be ideal.
That being said, I really serious in stating that I do not understand what this question is about. Support has been really helpful to me with previous questions but for some reason have not acknowledged this one (in spite of pointing it out several times) - either the problem I'm seeing and/or something I'm missing.
--------------------------
Question
2. (QID:BCM300) View the exhibit. The network administrator has configured router RT1 to provide interVLAN routing between the various subnets on the network. Based on the output provided by the show ip route command, what statement is true?
* Users will have full access to the Internet but will not be able to communicate with each other
* Because of the missing routing protocol, none of the VLANs can route traffic.
* Users on all VLANs can communicate with each other and access the Internet.
* Users can access all the resources on the network but cannot browse the Internet.
Stated solution
Correct Answer: Users will have full access to the Internet but will not be able to communicate with each other
Explanation:
If you compare the addressing information for VLAN 2 and VLAN 3, as shown on topology, it does not match the information displayed in the output of show ip route command.
C 10.1.1.0 is directly connected, Vlan 2
C 10.1.2.0 is directly connected, Vlan 3
Therefore, users will not be able to communicate with each other. However, using the static default route 0.0.0.0/0 1/0 via 200.1.1.2, users will have access to the Internet.
Topology
![[Image: tNDZkMQ]](http://omploader.org/tNDZkMQ)
Routing table on R1
![[Image: tNDZkMg]](http://omploader.org/tNDZkMg)
Lab Document:
http://routermatrix.net/config-labfiles/...bcm300.pdf
Better yet, if someone could 'un-stupid' me as to why the explanation makes any sense that would be very cool. However, I would be astounded if anyone has actually 'done' this scenario and could demonstrate results aligning with the question, solution and explanation.
Intuitively the solution seems incorrect, but I went ahead and 'did' this one in a lab (several times actually on both real gear and GNS3) to just to see the problem first hand. Just take a look at the host on Vlan3 (10.1.3.2/24) - why in the world would RT1 accept a packet on its SVI that does not match the prefix for that (ingress) interface (let alone a network address which does not exist locally at all)? This is the result of ARP debugging on RT1 in the lab when the host on Vlan 3 tries to leave the subnet:
RT1#debug arp
ARP packet debugging is on
RT1#
Mar 18 08:16:25.557: IP ARP req filtered src 10.1.3.2 c421.0bb4.0000, dst 10.1.3.1 0000.0000.0000 wrong cable, interface Vlan3
RT1#
Mar 18 08:16:27.561: IP ARP req filtered src 10.1.3.2 c421.0bb4.0000, dst 10.1.3.1 0000.0000.0000 wrong cable, interface Vlan3
RT1#
Mar 18 08:16:29.549: IP ARP req filtered src 10.1.3.2 c421.0bb4.0000, dst 10.1.3.1 0000.0000.0000 wrong cable, interface Vlan3
RT1#
The output 'wrong cable' does not strike me as particularly encouraging. Meanwhile, arp debugging on the router acting as host3 shows that it has no way to map its configured gateway IP to a link MAC address (dst 10.1.3.1 0000.0000.0000 FastEthernet0/0) - you can see the 2 second 'throttled' delay interval between retransmissions in the debugging timestamps:
host3#debug arp
ARP packet debugging is on
host3#ping 200.1.1.2 rep 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 200.1.1.2, timeout is 2 seconds:
.Mar 18 08:16:25.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
.Mar 18 08:16:26.565: IP ARP throttled out the ARP Request for 10.1.3.1
.Mar 18 08:16:27.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
.Mar 18 08:16:28.565: IP ARP throttled out the ARP Request for 10.1.3.1
.Mar 18 08:16:28.565: IP ARP throttled out the ARP Request for 10.1.3.1
.Mar 18 08:16:29.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
.Mar 18 08:16:30.565: IP ARP throttled out the ARP Request for 10.1.3.1.
Success rate is 0 percent (0/1)
host3#
.Mar 18 08:16:31.565: IP ARP: sent req src 10.1.3.2 c421.0bb4.0000,
dst 10.1.3.1 0000.0000.0000 FastEthernet0/0
host3#
Suffice it to say, the host on vlan 2 also has a gateway mismatch as well.
Information relevant to the question is supplied below. The url to the lab PDF documenting this scenario (qidbcm300.pdf), I think, demonstrates that the solution and explanation for this do not make sense. Again, if someone could point out something I'm overlooking that would be ideal.
That being said, I really serious in stating that I do not understand what this question is about. Support has been really helpful to me with previous questions but for some reason have not acknowledged this one (in spite of pointing it out several times) - either the problem I'm seeing and/or something I'm missing.
--------------------------
Question
2. (QID:BCM300) View the exhibit. The network administrator has configured router RT1 to provide interVLAN routing between the various subnets on the network. Based on the output provided by the show ip route command, what statement is true?
* Users will have full access to the Internet but will not be able to communicate with each other
* Because of the missing routing protocol, none of the VLANs can route traffic.
* Users on all VLANs can communicate with each other and access the Internet.
* Users can access all the resources on the network but cannot browse the Internet.
Stated solution
Correct Answer: Users will have full access to the Internet but will not be able to communicate with each other
Explanation:
If you compare the addressing information for VLAN 2 and VLAN 3, as shown on topology, it does not match the information displayed in the output of show ip route command.
C 10.1.1.0 is directly connected, Vlan 2
C 10.1.2.0 is directly connected, Vlan 3
Therefore, users will not be able to communicate with each other. However, using the static default route 0.0.0.0/0 1/0 via 200.1.1.2, users will have access to the Internet.
Topology
Routing table on R1
Lab Document:
http://routermatrix.net/config-labfiles/...bcm300.pdf