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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.

3
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3answers
1k 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 ...
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vote
1answer
87 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 ...
1
vote
1answer
170 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 (...
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vote
2answers
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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 (...
2
votes
2answers
312 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 ...
2
votes
1answer
577 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: ...
0
votes
1answer
81 views

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 ...
2
votes
1answer
9k 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 ...
8
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2answers
856 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 ...
3
votes
1answer
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 ...
21
votes
3answers
3k 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? ...
9
votes
3answers
658 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 ...