From: Gary Duncanson (gary.duncanson@googlemail.com)
Date: Thu Dec 06 2007 - 18:52:12 ART
What happens when a L3 switch receives a frame destined for a L3 destination
that is unknown to the router which has to recourse to a default route? Do
default route interfaces and outbound L2 headers get translated into FIB?
I think Odom covers some of this.
Gary
----- Original Message -----
From: "Scott Vermillion" <scott_ccie_list@it-ag.com>
To: "'Jian Gu'" <guxiaojian@gmail.com>; "'Gary Duncanson'"
<gary.duncanson@googlemail.com>
Cc: "'Darren Johnson'" <dazza_johnson@yahoo.co.uk>; <ccielab@groupstudy.com>
Sent: Thursday, December 06, 2007 9:41 PM
Subject: RE: [SPAM]Re: I know this CCIE who wouldn't know a packet if it hit
him in the ass! ~CCIE Interview Qs~
> Hey all,
>
> Certainly it's great to know what the process would be sans CEF/MLS, but
> in
> modern switching architectures, we aren't actually doing these lookups
> based
> on flows or packet/frame arrival, right? My studies of CEF for the
> written
> caused me to look a little more deeply into this than I ever had
> previously.
> What I recall (and what Joe's article seems to confirm) is that
> information
> populated into the RIB gets translated into a FIB by CEF. Then the
> adjacency table actually caches the full L2 header for each and every
> entry
> in the FIB.
>
> So before the first flow ever takes place, we've already pre-calculated
> not
> only the outgoing interface for every L3 destination, we've also cached
> the
> outbound L2 header. This all gets pushed down to ASICs that essentially
> match on bit patterns. In other words, both L2 and L3 are switched down
> in
> hardware and all of this is set up at system boot time. Then the RP
> simply
> pushes changes in the RIB over to CEF, which maintains the FIB.
>
> Now where I get a bit fuzzy is how QoS policy and that sort of thing gets
> inserted into the mix. I'm not a chip designer and I don't aspire to be.
> I'm willing to take some things on faith, and this is probably one such
> thing.
>
> And I understand you too Darren! A host or another router viewing the
> local
> box in question as the next hop would perform L2 encapsulation with the
> destination MAC set to that of this local box. But I still think that,
> due
> to CEF, in such a case we're still just dealing with a L3 switching
> operation vs. a L2 switching operation.
>
> Right?
>
> Scott
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Jian
> Gu
> Sent: Thursday, December 06, 2007 2:12 PM
> To: Gary Duncanson
> Cc: Darren Johnson; ccielab@groupstudy.com
> Subject: Re: [SPAM]Re: I know this CCIE who wouldn't know a packet if it
> hit
> him in the ass! ~CCIE Interview Qs~
>
> Assuming MACs are leaned and ARPs are all resolved.
>
> When a frame comes in, router/switch will do both L2 and L3 lookup at the
> same time, and combine the result to make the final decision. If
> destination
> MAC is router, then L2 lookup will not yield something meaningful, L3
> lookup will come out with MAC re-write information for nexthop for
> destination IP, frame will then be routed. If destination MAC is not
> router,
> this MAC must be in the vlan's dynamic MAC table, in this case, L2 lookup
> will yield outgoing port, L3 lookup better come with the same result, this
> frame will be L2 switched.
>
> Jian
>
> On Dec 6, 2007 12:40 PM, Gary Duncanson <gary.duncanson@googlemail.com>
> wrote:
>
>> Daz,
>>
>> Yeah. Well it's getting later here in GB.
>>
>> Packet comes in..
>>
>> If the destination MAC address is that of the L3 switch, then it knows
>> about
>> it, doesn't it just switch it out the right interface?
>>
>> If unknown..what about ARP or routing?
>>
>> Im sure you know what you mean :-)
>>
>> Gaz
>> ----- Original Message -----
>> From: "Darren Johnson" <dazza_johnson@yahoo.co.uk>
>> To: "'Gary Duncanson'" <gary.duncanson@googlemail.com>
>> Cc: <ccielab@groupstudy.com>
>> Sent: Thursday, December 06, 2007 8:33 PM
>> Subject: RE: [SPAM]Re: I know this CCIE who wouldn't know a packet if it
>> hit
>> him in the ass! ~CCIE Interview Qs~
>>
>>
>> > Hey Gaz, starting to like our late night chats ;-)
>> >
>> > My point was that if the destination MAC address is that of the L3
>> switch,
>> > it is to be routed. If it isn't and the receiving interface is L2 then
>> it
>> > is
>> > switched/bridged.
>> >
>> > Hmmm, not sure if Im making myself clear. I know what I mean...... :-)
>> >
>> > Daz
>> >
>> > -----Original Message-----
>> > From: Gary Duncanson [mailto:gary.duncanson@googlemail.com]
>> > Sent: 06 December 2007 19:50
>> > To: Darren Johnson
>> > Cc: ccielab@groupstudy.com
>> > Subject: [SPAM]Re: I know this CCIE who wouldn't know a packet if it
>> > hit
>> > him
>> > in the ass! ~CCIE Interview Qs~
>> >
>> > Would that not be destination MAC known by the L3 switch (switched) as
>> > opposed to unknown (routed)?
>> >
>> > Is it not switched instead of bridged ;) What about those damn ASICs?
>> > I
>> > have chatted offline with a guru who suspects CEF is the route of the
>> evil
>> > these days (no pun intended) as opposed to the MLS-SE, MLS-RP, MLSP
>> stuff
>> > and he may comment soon.
>> >
>> > You know who you are ;)
>> > ----- Original Message -----
>> > From: "Darren Johnson" <dazza_johnson@yahoo.co.uk>
>> > To: "'Gary Duncanson'" <gary.duncanson@googlemail.com>; "'Jian Gu'"
>> > <guxiaojian@gmail.com>
>> > Cc: <ccielab@groupstudy.com>
>> > Sent: Thursday, December 06, 2007 7:28 PM
>> > Subject: RE: I know this CCIE who wouldn't know a packet if it hit him
>> in
>> > the ass! ~CCIE Interview Qs~
>> >
>> >
>> >> IMHO, if the destination MAC is owned by the L3 switch, then it needs
>> to
>> >> be
>> >> routed. If the destination MAC is not owned by the L3 switch, it can
>> >> either
>> >> bridge it (if the device is located on another interface) or drop it
>> (if
>> >> the
>> >> device is located on the same interface the frame was received on).
>> >>
>> >> Dazzler
>> >>
>> >> -----Original Message-----
>> >> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>> >> Of
>> >> Gary
>> >> Duncanson
>> >> Sent: 06 December 2007 17:51
>> >> To: Jian Gu
>> >> Cc: ccielab@groupstudy.com
>> >> Subject: Re: I know this CCIE who wouldn't know a packet if it hit him
>> in
>> >> the ass! ~CCIE Interview Qs~
>> >>
>> >> Sounds like the route once switch many thing to me from MLS studies..
>> >>
>> >> Gary
>> >> ----- Original Message -----
>> >> From: "Jian Gu" <guxiaojian@gmail.com>
>> >> To: "Sohail Nedaria" <sohail.nedaria@gmail.com>
>> >> Cc: "ccie ccie" <cciefun@gmail.com>; "Narbik Kocharians"
>> >> <narbikk@gmail.com>; "Cisco certification" <ccielab@groupstudy.com>
>> >> Sent: Thursday, December 06, 2007 6:54 AM
>> >> Subject: Re: I know this CCIE who wouldn't know a packet if it hit him
>> in
>> >> the ass! ~CCIE Interview Qs~
>> >>
>> >>
>> >>> Sure, here is one I like,
>> >>>
>> >>> How does a L3 switch router know when to L2 switch an incoming frame
>> and
>> >>> when to L3 switch an incoming frame?
>> >>>
>> >>> On Dec 5, 2007 10:00 PM, Sohail Nedaria <sohail.nedaria@gmail.com>
>> >>> wrote:
>> >>>
>> >>>> Hi Guys
>> >>>>
>> >>>> Can you guys provide me CCIE Interview questions so i
>> can
>> >>>> also prepare my self well before i take on any interview.
>> >>>>
>> >>>> Thanks
>> >>>> Suhail
>> >>>> CCIE#19337
>> >>>>
>> >>>>
>> >>>> On 12/6/07, ccie ccie <cciefun@gmail.com> wrote:
>> >>>> >
>> >>>> > Hi,
>> >>>> >
>> >>>> > I am going off bit, but like to share something with you.
>> >>>> >
>> >>>> > I gave lots of interview include CISCO, Google, Yahoo......no end
>> >>>> > &
>> i
>> >>>> gave
>> >>>> > with out any interest to join but to test myself :). I gave
>> >>>> > interview
>> >>>> for
>> >>>> > small to big organization & i found you can't impress the
>> interviewer
>> >>>> only
>> >>>> > by your techniqual knowledge.
>> >>>> >
>> >>>> > Thing to impress them as per my understanding are as.
>> >>>> >
>> >>>> > 1. Good Techniqual Approach
>> >>>> > 2. If you dont know say you dont know this time, but you will
>> >>>> > learn
>> &
>> >>>> find
>> >>>> > the answer.
>> >>>> > 3. Good troubleshooting approach (In network always answer withh
>> >>>> refrance
>> >>>> > to
>> >>>> > OSI layer)
>> >>>> > 4. Listen interviewer carefully take own time to think & answer
>> >>>> > 5. Never underestimate interviewer who knows what the other side
>> >>>> > person
>> >>>> > is.
>> >>>> > 6. Respect interviwer & appreciate him for some good question.
>> >>>> > 7. Before go to the interview do your study about the oganization.
>> >>>> > 8. Last be not least. Give an impression that you respect the
>> >>>> organization
>> >>>> > lot, you will love to work for them, you will give longer
>> association
>> >>>> > &
>> >>>> > your
>> >>>> > placement in organization will contributing lot to generate
>> revenue.
>> >>>> >
>> >>>> > Dont forget final interview is always by the management people.
>> >>>> >
>> >>>> >
>> >>>> > Regards,
>> >>>> > Mike
>> >>>> >
>> >>>> >
>> >>>> >
>> >>>> > On 12/6/07, Narbik Kocharians <narbikk@gmail.com> wrote:
>> >>>> > >
>> >>>> > > Darth, Are you a CCIE? I don't see your number. But what would
>> you
>> >>>> hate
>> >>>> > to
>> >>>> > > be asked in the interview? that's the question i would ask.
>> >>>> > > I would ask him/her what are your weak points and what are your
>> >>>> > > strong
>> >>>> > > points. Go from there.
>> >>>> > > Talk to him/her about some of the problems that your firm had
>> >>>> > > and
>> >>>> > > see
>> >>>> > > what the person responds, but don't expect the poor CCIE to
>> >>>> > > solve
>> >>>> > > it
>> >>>> for
>> >>>> > > you
>> >>>> > > in a second. But he/she should have an idea as to where to look,
>> >>>> > > from
>> >>>> > that
>> >>>> > > you should know the depth of his/her knowledge.
>> >>>> > > If you or the interviewer is experienced enough, the second this
>> >>>> person
>> >>>> > > opens his/her mouth, you should know the depth of his knowledge.
>> >>>> > >
>> >>>> > > But once again, CCIEs are not gods, they can have a bad day as
>> >>>> > > well.
>> >>>> > > I
>> >>>> > > personally like to focus on the person's attitude and
>> personality,
>> >>>> > > obviously
>> >>>> > > he/she got the CCIE cert, which means that the person either
>> knows
>> >>>> > > or
>> >>>> > knew
>> >>>> > > the stuff and can easily pick up the info.
>> >>>> > >
>> >>>> > >
>> >>>> > > My 2 Cent.
>> >>>> > >
>> >>>> > > On 12/5/07, darth router <darklordrouter@gmail.com> wrote:
>> >>>> > > >
>> >>>> > > > Ok guys,
>> >>>> > > >
>> >>>> > > > there was a thread a while back talking about dumbass CCIE's.
>> As
>> >>>> > > > I
>> >>>> > > prefer
>> >>>> > > > not to be the dumbest CCIE on the planet, help me out with
>> >>>> > > > questions
>> >>>> > > that
>> >>>> > > > you might ask a CCIE candidate in an interview. I have had
>> >>>> > > > some
>> >>>> brutal
>> >>>> > > > interviews since I became IE. Honestly the questions seem a
>> >>>> > > > bit
>> >>>> basic
>> >>>> > so
>> >>>> > > > far, but I have had some really in depth questions about
>> >>>> > spanning-tree,
>> >>>> > > > troubleshootin real world EIGRP scenarios, etc.. that really
>> >>>> > > > caught
>> >>>> me
>> >>>> > > off
>> >>>> > > > guard. It's not that I could not have solved these issues, had
>> I
>> >>>> been
>> >>>> > > > there
>> >>>> > > > logged into the routers, its explaining things we take for
>> >>>> > > > granted
>> >>>> can
>> >>>> > > be
>> >>>> > > > tough, especially in interviews. It seems like a lot of
>> >>>> > > > people are amazed that a CCIE couldn't answer this or that
>> >>>> > > > question.
>> >>>> > > > Personally, I am trying to come up with a knowledge
>> >>>> > > > maintanance
>> >>>> plan,
>> >>>> > > > like reading a chapter in the exam cert guide every week. The
>> >>>> > > > tasks
>> >>>> I
>> >>>> > > > do not do on a daily basis fade quickly.
>> >>>> > > >
>> >>>> > > >
>> >>>> > > > I have of late been going way back to basics, reading up on
>> >>>> > > > TCP/IP
>> >>>> > > flows,
>> >>>> > > > Ethernet, ARP, looking at packet sniffing traces, etc..
>> >>>> > > > Someone
>> >>>> > > > made
>> >>>> > > > mention
>> >>>> > > > of the CAM table populating entries, so I read up on that too.
>> >>>> > > >
>> >>>> > > > I certainly don't know everything, but I would love to. Care
>> >>>> > > > to
>> >>>> > > > give
>> >>>> > me
>> >>>> > > > some
>> >>>> > > > example questions you might ask a CCIE in an interview, or
>> >>>> > technologies
>> >>>> > > > you
>> >>>> > > > would expect to have him/her to have down pat?
>> >>>> > > >
>> >>>> > > > DR
>> >>>> > > >
>> >>>> > > >
>> >>>> >
>> > _______________________________________________________________________
>> >>>> > > > Subscription information may be found at:
>> >>>> > > > http://www.groupstudy.com/list/CCIELab.html
>> >>>> > > >
>> >>>> > >
>> >>>> > >
>> >>>> > >
>> >>>> > > --
>> >>>> > > Narbik Kocharians
>> >>>> > > CCIE# 12410 (R&S, SP, Security)
>> >>>> > > CCSI# 30832
>> >>>> > > www.MicronicsTraining.com
>> >>>> > > Sr. Technical Instructor
>> >>>> > > www.Net-WorkBooks.com
>> >>>> > >
>> >>>> > >
>> >>>>
>> _______________________________________________________________________
>> >>>> > > Subscription information may be found at:
>> >>>> > > http://www.groupstudy.com/list/CCIELab.html
>> >>>> >
>> >>>> >
>> > _______________________________________________________________________
>> >>>> > Subscription information may be found at:
>> >>>> > http://www.groupstudy.com/list/CCIELab.html
>> >>>> >
>> >>>>
>> >>>>
>> >>>>
>> >>>> --
>> >>>> Thanks And Regards
>> >>>> Suhail.U.Nedaria
>> >>>> 9833256425
>> >>>> CCIE# 19337.
>> >>>>
>> >>>>
>> _______________________________________________________________________
>> >>>> Subscription information may be found at:
>> >>>> http://www.groupstudy.com/list/CCIELab.html
>> >>>
>> >>>
>> _______________________________________________________________________
>> >>> Subscription information may be found at:
>> >>> http://www.groupstudy.com/list/CCIELab.html
>> >>
>> >> _______________________________________________________________________
>> >> Subscription information may be found at:
>> >> http://www.groupstudy.com/list/CCIELab.html
>> >>
>> >>
>> >>
>> >> ___________________________________________________________
>> >> Does your mail provider give you FREE antivirus protection?
>> >> Get Yahoo! Mail http://uk.mail.yahoo.com
>> >>
>> >
>> >
>> >
>> > ___________________________________________________________
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>>
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>
> _______________________________________________________________________
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