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Some questions about OSPF / DHCP / VLAN
FreddyIW
Member Posts: 27 ■□□□□□□□□□
in CCNA & CCENT
Hello, I want to ask about these questions I got in my academy that I found confusing / weird. Could anyone provide some explanation why?
(Green = correct answer)
1) What happens immediately after two OSPF routers have exchanged hello packets and have formed a neighbor adjacency?
a) They request more information about their databases.
b) They negotiate the election process if they are on a multiaccess network.
c) They exchange DBD packets in order to advertise parameters such as hello and dead intervals.
d) They exchange abbreviated lists of their LSDBs
^
Why isn't "B" the correct answer? Don't the routers elect DR / BDR first if they are on a multiaccess network?
2) Which kind of message is sent by a DHCP client when its IP address lease has expired?
a) a DHCPREQUEST unicast message
b) a DHCPREQUEST broadcast message
c) a DHCPDISCOVER broadcast message
d) a DHCPDISCOVER unicast message
^
I think the correct answer should be "C", isn't it? After expiration, the DHCP client would start everything from zero right?
3) What is the purpose of setting the native VLAN separate from data VLANs?
a) The native VLAN is for routers and switches to exchange their management information, so it should be different from data VLANs.
b) A separate VLAN should be used to carry uncommon untagged frames to avoid bandwidth contention on data VLANs.
c) The native VLAN is for carrying VLAN management traffic only.
d) The security of management frames that are carried in the native VLAN can be enhanced
^
Why is "B" correct? What about "A"? What does management information mean here? Does it refer to protocol like CDP, VTP, etc?
4) What is a function of the distribution layer?
a) interconnection of large-scale networks in wiring closets
b) network access to the user
c) fault isolation
d) high-speed backbone connectivity
^
Isn't "A" the function of the core layer? What I know is that distribution layer acts as layer 3 routing boundaries for all the access layer switches.
(Green = correct answer)
1) What happens immediately after two OSPF routers have exchanged hello packets and have formed a neighbor adjacency?
a) They request more information about their databases.
b) They negotiate the election process if they are on a multiaccess network.
c) They exchange DBD packets in order to advertise parameters such as hello and dead intervals.
d) They exchange abbreviated lists of their LSDBs
^
Why isn't "B" the correct answer? Don't the routers elect DR / BDR first if they are on a multiaccess network?
2) Which kind of message is sent by a DHCP client when its IP address lease has expired?
a) a DHCPREQUEST unicast message
b) a DHCPREQUEST broadcast message
c) a DHCPDISCOVER broadcast message
d) a DHCPDISCOVER unicast message
^
I think the correct answer should be "C", isn't it? After expiration, the DHCP client would start everything from zero right?
3) What is the purpose of setting the native VLAN separate from data VLANs?
a) The native VLAN is for routers and switches to exchange their management information, so it should be different from data VLANs.
b) A separate VLAN should be used to carry uncommon untagged frames to avoid bandwidth contention on data VLANs.
c) The native VLAN is for carrying VLAN management traffic only.
d) The security of management frames that are carried in the native VLAN can be enhanced
^
Why is "B" correct? What about "A"? What does management information mean here? Does it refer to protocol like CDP, VTP, etc?
4) What is a function of the distribution layer?
a) interconnection of large-scale networks in wiring closets
b) network access to the user
c) fault isolation
d) high-speed backbone connectivity
^
Isn't "A" the function of the core layer? What I know is that distribution layer acts as layer 3 routing boundaries for all the access layer switches.
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OfWolfAndMan
Member Posts: 923 ■■■■□□□□□□
1. Remember this for OSPF adjacencies, in this order:
a. Down (Initial State
b. Init (A packet has been received from another router)
c. 2-way (Bi-directional communication. DR/BDR Election occur at this stage). This is the state DRothers maintain with each other in a multi-access segment, assuming the network type is set to broadcast/nonbroadcast.
d. Exstart (Routers identify master/slave for LSDB synchronization. Highest IP becomes master. Remember loopbacks are prioritized over standard links)
e. Exchange (DBD exchange)
f. Loading (LSRs received for outdated LSAs
g. Full (Neighbors fully adjacent)
2. After the client has already requested from the server, it now will prefer that server in the future (Unless you tell it to stop), and will send a unicast request packet after its lease expires. DHCPDISCOVER is only for the initial allocation process.
3. Not sure who came up with that.
4. D would be more appropriate for the core, but it does interconnect the access and core. Play of words, really and somewhat vague.:study:Reading: Lab Books, Ansible Documentation, Python Cookbook 2018 Goals: More Ansible/Python work for Automation, IPSpace Automation Course [X], Build Jenkins Framework for Network Automation [] -
OptionsFreddyIW
Member Posts: 27 ■□□□□□□□□□
OfWolfAndMan wrote: »1. Remember this for OSPF adjacencies, in this order:
a. Down (Initial State
b. Init (A packet has been received from another router)
c. 2-way (Bi-directional communication. DR/BDR Election occur at this stage). This is the state DRothers maintain with each other in a multi-access segment, assuming the network type is set to broadcast/nonbroadcast.
d. Exstart (Routers identify master/slave for LSDB synchronization. Highest IP becomes master. Remember loopbacks are prioritized over standard links)
e. Exchange (DBD exchange)
f. Loading (LSRs received for outdated LSAs
g. Full (Neighbors fully adjacent)
2. After the client has already requested from the server, it now will prefer that server in the future (Unless you tell it to stop), and will send a unicast request packet after its lease expires. DHCPDISCOVER is only for the initial allocation process.
3. Not sure who came up with that.
4. D would be more appropriate for the core, but it does interconnect the access and core. Play of words, really and somewhat vague.
Hello wolf, thanks for your answer.
As for question 2, I think the correct answer should be DHCPDISCOVER broadcast. When the lease has already expired, the client has to start everything again from zero. DHCPREQUEST unicast is used when 50% of the total lease time has been used (but that's not expired yet). This is the reference I used: https://technet.microsoft.com/en-us/library/cc958935.aspx -
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Dieg0M
Member Posts: 861
No. When the lease timer expires the client sends a unicast DHCPREQUEST to the original leasing server. If the server does not respond, then it will reset and send a DHCPDISCOVER.Follow my CCDE journey at www.routingnull0.com