CEF & Fast Switching
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CEF Quick summary: Cisco Express Forwarding (CEF) provides the ability to switch packets through a device in a very quick and efficient way while also keeping the load on the router’s processor low. CEF is made up of two different main components: the Forwarding Information Base (FIB) and the Adjacency Table. These are automatically updated at the same time as the routing table. The adjacency table is tasked with maintaining the layer 2 next-hop information for the FIB. Adjacency Types That Require Special Handling: Glean adjacency – in short when the router is directly connected to hosts the FIB table on the router will maintain a prefix for the subnet rather than for the individual host prefix. This subnet prefix points to a GLEAN adjacency. A glean adjacency entry indicates that a particular next hop should be directly connected, but there is no MAC header rewrite information available. When the device needs to forward packets to a specific host on a subnet, Cisco Express Forwarding requests an ARP entry for the specific prefix, ARP sends the MAC address, and the adjacency entry for the host is built. Other special adjacency types are Discard adjacency and Drop adjacency but they are not mentioned here. |
Question 1
Explanation
The command “show ip cef” is used to display the CEF Forwarding Information Base (FIB) table. There are some entries we want to explain:
+ If the “Next Hop” field of a network prefix is set to receive, the entry represents an IP address on one of the router’s interfaces. In this case, 192.168.201.2 and 192.168.201.31 are IP addresses assigned to interfaces on the local router.
+ If the “Next Hop” field of a network prefix is set to attached, the entry represents a network to which the router is directly attached. In this case the prefix 192.168.201.0/27 is a network directly attached to router R2’s Fa0/0 interface.
But there are some special cases:
+ The all-0s host addresses (for example, 192.168.201.0/32) and the all-1s host addresses (not have in the output above but for example, 192.168.201.255/32) also show as receive entries.
+ 255.255.255.255/32 is the local broadcast address for a subnet
+ 0.0.0.0/32: maybe it is a reserved link-local address
+ 0.0.0.0/0: This is the default route that matching all other addresses (also known as “gateway of last resort”). In this case it points to 192.168.201.1 -> Answer C is correct.
Reference: CCNP Routing and Switching ROUTE 300-101 Official Cert Guide
Question 2
Explanation
The “show adjacency” command is used to display information about the Cisco Express Forwarding adjacency table or the hardware Layer 3-switching adjacency table.
There are two known reasons for an incomplete adjacency:
+ The router cannot use ARP successfully for the next-hop interface.
+ After a clear ip arp or a clear adjacency command, the router marks the adjacency as incomplete. Then it fails to clear the entry.
Note: Two nodes in the network are considered adjacent if they can reach each other using only one hop.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/17812-cef-incomp.html
Question 3
Explanation
The “show ip cache” command displays the contents of a router’s fast cache. An example of the output of this command is shown below:
Note: If CEF is disabled and fast switching is enabled, the router begins to populate its fast cache.
Question 4
Question 5
Explanation
Cisco Express Forwarding (CEF) provides the ability to switch packets through a device in a very quick and efficient way while also keeping the load on the router’s processor low. CEF is made up of two different main components: the Forwarding Information Base (FIB) and the Adjacency Table. These are automatically updated at the same time as the routing table.
The adjacency table is tasked with maintaining the layer 2 next-hop information for the FIB.
Question 6
Explanation
The explanation of this question is too lengthy so we recommend to read this article: http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/26083-trouble-cef.html
Question 7
Explanation
Glean adjacency – in short when the router is directly connected to hosts the FIB table on the router will maintain a prefix for the subnet rather than for the individual host prefix. This subnet prefix points to a GLEAN adjacency.
Punt adjacency – When packets to a destination prefix can’t be CEF Switched, or the feature is not supported in the CEF Switching path, the router will then use the next slower switching mechanism configured on the router.
Question 8
Explanation
Nodes in the network are said to be adjacent if they can reach each other with a single hop across a link layer. In addition to the FIB, CEF uses adjacency tables to prepend Layer 2 addressing information. The adjacency table maintains Layer 2 next-hop addresses for all FIB entries.
Reference: https://www.cisco.com/c/en/us/td/docs/ios/12_2/switch/configuration/guide/fswtch_c/xcfcef.html
Question 9
Is the 183q worth looking at, or stick to TAGWA and 149q????
Hi All,
Can anyone help me with 183q dumps vinothayyavu @ gmail . com
can somebody tell me please that what is the last question of 40Q of TAGWA , in my life there is no answer of question “Meaning of priority 0 configured in ospf router?” .
can somebody tell me please that what is the last question of 40Q of TAGWA , in my life there is no answer of question “Meaning of priority 0 configured in ospf router?” . Plus what it the correct answer for the following questions?
Question 2
Refer to the following configuration command.
router(config)# ip nat inside source static tcp 172.16.10.8 8080 172.16.10.8 80
Which statement about the command is true?
A. Any packet that is received in the inside interface with a source IP port address of
172.16.10.8:80 is translated to 172.16.10.8:8080.
B. Any packet that is received in the inside interface with a source IP port address of
172.16.10.8:8080 is translated to 172.16.10.8:80.
C. The router accepts only a TCP connection from port 8080 and port 80 on IP address
172.16.10.8.
D. Any packet that is received in the inside interface with a source IP address of 172.16.10.8
is redirected to port 8080 or port 80.
Answer:?
and
Question 28
A network engineer wants to ensure an optimal end-to-end delay bandwidth product. The delay is
less than 64 KB. Which TCP feature ensures steady state throughput?
A. Window scaling
B. Network buffers
C. Round-trip timers
D. TCP acknowledgments
Answer:?
some people said the answer are wrong of TAGWA file. Please help
Question 2
Answer: B.
http://www.cisco.com/image/gif/paws/13772/12.pdf
ip nat inside source static tcp 172.16.10.8 8080 172.16.10.8 80
!−−− Static NAT command that states any packet received in the inside
!−−− interface with a source IP address of 172.16.10.8:8080 is
!−−− translated to 172.16.10.8:80.
Thanks and what will the answer of these following questions. Please
Question 28
A network engineer wants to ensure an optimal end-to-end delay bandwidth product. The delay is
less than 64 KB. Which TCP feature ensures steady state throughput?
A. Window scaling
B. Network buffers
C. Round-trip timers
D. TCP acknowledgments
Answer:?
and
what is the last question of 40Q of TAGWA file , in my file there is no answer of question “Meaning of priority 0 configured in ospf router?”
Some really good blog posts on this web site, regards for contribution. “When he has ceased to hear the many, he may discern the One – the inner sound which kills the outer.” by H Hahn Blavatsky.
http://www.ZuqRgWtWvY.com/ZuqRgWtWvY
To Jane:
Meaning of priority 0 configured in ospf router.
Router won’t participate/cosnider for OSPF DR/BDR election.
Thanks and what will the answer of these following questions. Please
Question 28
A network engineer wants to ensure an optimal end-to-end delay bandwidth product. The delay is
less than 64 KB. Which TCP feature ensures steady state throughput?
A. Window scaling
B. Network buffers
C. Round-trip timers
D. TCP acknowledgments
Answer:
B. Network buffers
Hi all, I’m taking the exam tomorrow, can anyone pass me the latest dump for the 300-101 please? gusgestal hotmail com . Thanks
To Gus
Hi Gus can you tell me the questions after you took exam. my email is htikeaungkyaw14 icloud.com. I also need to study thx
What is TAQWA please, is there any website that I can get it from?
@Jane woken
“question “Meaning of priority 0 configured in ospf router?” is that the router does not participate in DR election process.
please someone email me the newest dump narcisse.aspilaire at gmail thank you in advance, anything that
There are new question in Route 300-101 exam Please help aswering it?
How to fix routing loops?
filtering upper layer protocols?
And many more which we are out of clue!!!
hi all, the answer for 4 question in CEF is “D” not “B”
Hi salman, everybody tell that the coorection answer for the 4 question is “B” but I don’t have the explication for it.
Hello anyone, can you help me with the dumps Route and TSHOOT?
My e-mail is: info AT anemosradio.com
Thank you!
Anyone able to share the valid dump ?
incredibletbf @ hotmail . com
Thank you in advance !
miguelfilipe_20_01 @ hotmail . com
can u guys please sende me the latest dumps on miguelfilipe_20_01 @ hotmail . com
Can someone please send the latest brain dump {email not allowed}
Passed,
The IT-Libraries 358q dumps are 80% valid.
@Anonymous on July 20th.. Can you share those please? Or do have a link?
please share IT-Libraries 358q or any link to dhan84 @ protomail . com
thanks :)
Can I get the IT-Libraries please? elzy_1974 @ yahoo.com
Excuse me ! where can i see question 5,6 ,7 and other all question update from this digitaltut ? thanks all
Hello guys i cant login the site? there was any change?
Hello everyone, for latest valid dump with continuous update, please contact me at steffyshirls @ gmail .com
WHY? How does an IOS router process a packet that should be switched by Cisco Express Forwarding without an FIB entry?
A. by forwarding the packet
B. by dropping the packet (CORRECT)
C. by creating a new FIB entry for the packet
D. by looking in the routing table for an alternate FIB entry
WHY DO THE ROUTER DROP THE PACKRT?I think it just build a new entry
what do you think?
Passed today,
used the new dumps from IT-Libraries, pay extra attention to the labs since it’s easy to mess up (happened to me)
jg can you share it-libraries dump please
Can someone shoot me the IT-Libraries Dumps, please? ajmchie at hotmail dot com. Thank you!
Guys anyone having dumps, my CCNP expiring this month and I m left with Route
My email address – {email not allowed}
penigimahidhar at gmail dot come
Guys anyone having dumps, my CCNP expiring this month and I m left with Route
penigimahidhar at gmail dot come
You saved me a lot of hassle just now. No complaints on this end, simply a cool piece. That cleared it up for me. The people you love are lucky to have you in their lives. Your stuff is so awesome that my eyeballs exploded while reading it.
https://www.instapaper.com/p/6096832
Passed, if you go the exam study the 440q dumps.
Passed with the 539q dumps, all questions were from there.
Hi everyone, I have the valid dump with me and I’m wiling to share. Please contact me via durshen81 @ gmail .com
539q anyone have it in vce format?
Confirming the 440q dumps are valid.
Hi guys, I’m having the valid dump with me and I’m wiling to share. Please contact me via durshen81 @ gmail .com
Hi guys, I have the valid dump with me and I’m wiling to share. Please contact me via durshen81 @ gmail .com
Where do can find this 440q dump?
latest dumps ccnp
dumpspro.com/ccnp-dumps
WHY? How does an IOS router process a packet that should be switched by Cisco Express Forwarding without an FIB entry?
A. by forwarding the packet
B. by dropping the packet (CORRECT)
C. by creating a new FIB entry for the packet
D. by looking in the routing table for an alternate FIB entry
WHY DO THE ROUTER DROP THE PACKRT?I think it just build a new entry
what do you think?
*** FIB table is created from the Routing table, so if the router does not have a route for this packet, it will drop the packet
Question 28
A network engineer wants to ensure an optimal end-to-end delay bandwidth product. The delay is
less than 64 KB. Which TCP feature ensures steady state throughput?
A. Window scaling
B. Network buffers
C. Round-trip timers
D. TCP acknowledgments
Answer is B ***Please read Global Synchronization and the RED behavior
Question 28
A network engineer wants to ensure an optimal end-to-end delay bandwidth product. The delay is
less than 64 KB. Which TCP feature ensures steady state throughput?
A. Window scaling
B. Network buffers
C. Round-trip timers
D. TCP acknowledgments
Answer is A ***Please read Global Synchronization and the RED behavior
*** Sorry is A, window scaling LoL
For Q9 A, B, C is correct, as mentioned:
#ip cef load-sharing algorithm ?
include-ports Algorithm that includes layer 4 ports
original Original algorithm
tunnel Algorithm for use in tunnel only environments
universal Algorithm for use in most environments