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Questions tagged [cef]

For questions about Cisco Express Forwarding (CEF). For instance, you want to enable CEF on your Cisco 6500 Series, but need help doing so.

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Is the routing table a control plane concept or a data plane concept?

I've always been told that the routing table is a control plane concept. You build this table, collect the routes, the way they were learned, their metrics, and so on. You then use this information to ...
Mitrixsen's user avatar
  • 877
0 votes
2 answers
96 views

Do Forwarding Table (FIB not LFIB) have MPLS label?

In my opinion, FIB doesn't have MPLS label, FIB should be populate from RIB because of CEF. However, after I seach online and find out that some tutorial stated that FIB also contains the label just ...
jacky chong's user avatar
-1 votes
2 answers
145 views

Cisco express forwarding

I'm studying CEF and I'm confused with these terms : Route processor, forwarding engine, centralized and distributed forwarding, npu So my questions is is the RP a hardware component or an ios ...
user67877's user avatar
0 votes
0 answers
1k views

when to disable CEF on an interface

i am currently learning about CEF and i came across the command "no ip route-cache cef", which i do understand what it does, essentially, it enables Fast-switching/process switching on an interface. ...
Gngogh's user avatar
  • 327
2 votes
1 answer
219 views

What is a meaning of Load balancing Hash

What does Load balancing Hash mean in CEF? Which commands are use to configure? Is it support to other vendors except Cisco? If it is not support other vendors? do they have any similar concept? Which ...
infra's user avatar
  • 3,138
3 votes
3 answers
3k views

Switching methods (CEF, hardware, software, TCAM table)

Currently studying the switching methods, someone could confirm to me the assumptions as follows ? I also would have some questions. Generally the layer-2 switches have ASIC components with CAM ...
bdes31's user avatar
  • 1,085
1 vote
1 answer
176 views

How does Software CEF (Cisco`s techonology) implement prefix search algorithm?

How does the software version of CEF (Cisco`s technology for speeding up packet switching) implement algorithm to search prefixes in FIB (Forwarding Information Base)? Does it use a hash table or ...
Евгений Артеменко's user avatar
1 vote
1 answer
300 views

mls cef maximum-routes

Cisco#show mls cef maximum-routes FIB TCAM maximum routes : ======================= Current :- ------- IPv4 - 1000k MPLS - 8k (default) IPv6 + IP Multicast - 8k (...
Simon's user avatar
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1 vote
2 answers
3k views

Switching vs Routing

I have seen quite a few discussions regarding MPLS stating things like: MPLS combines the performance and capabilities of Layer 2 (data link layer) switching with the proven scalability of Layer 3 (...
fsociety's user avatar
  • 905
2 votes
4 answers
577 views

Is Longest Prefix Matching(LPM) Done in Data or Control Plane?

I have a strong confusion on this whether LPM is done in Data or Control Plane. My thoughts on this is as follows if its in data plane, we will have to do it for every packet hence we will have a ...
Jaugust's user avatar
  • 123
2 votes
1 answer
1k views

ISP HA using GLBP vs BGP

I have a tech startup environment where I'm replacing consumer-grade routers with enterprise-grade. Now, they are asking if we can have dual ISPs to minimize downtime and any disruption. I have: ...
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1 answer
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Looping back through switches?

Please look at the attached topology I am studying for CCNP with ine.com, and I have got a lab switch they say is possible, I say it is not (with the current config) SW-3 config Fa 0/15 no ...
psniffer's user avatar
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2 votes
2 answers
11k views

Can't ping a router's interface which is in a WAN directly connected to my router- (Packet tracer)

Here s a pic from packet tracer What I'm trying to do is to ping Router3's Se2/0 interface from PC0.(Or Router2's Se2/0 interface from PC1) However the ping message gets only as far as the Router2's ...
MattSt's user avatar
  • 123
8 votes
2 answers
1k views

Where is Cisco Hardware dCEF's adjacency table stored?

For Cisco Hardware dCEF, based on some documents published on Cisco website, at the ingress line card/interface, conceptually it looks up the FIB with dst IP address, and gets a pointer to an ...
wei's user avatar
  • 203
3 votes
1 answer
1k views

All switching on cisco 3750 done by cpu

A little confused.. When trouble shooting excessive output drops on a 3750 i noticed that al switching is done by cpu instead of "route cache". This 3750 has no ip routing enabled and no ip cef (ip ...
user209's user avatar
  • 894
21 votes
3 answers
4k views

CEF operations on L3 switch vs router

I understand that L3 switches use CEF for faster packet forwarding. However, CEF will not work for packets that need to undergo NAT. Does this mean CEF isn't used by edge routers and edge L3 switches? ...
Michael May's user avatar
  • 1,005
9 votes
3 answers
718 views

Why does "show adjacency" take so long to run?

Why does the "show adjacency" command take so long to run (in the order of minutes) on Cisco IOS Software, 7200 Software (C7200P-SPSERVICESK9-M), Version 12.4(4)XD5, RELEASE SOFTWARE (fc1)? The ...
generalnetworkerror's user avatar