At 08:29 AM 7/11/01, Stephen Skinner wrote:
>Howdy chaps....
>
>this is all good but i have a question
>
>Router B sends update directly to Router A specifying 4 networks
>
>HOW....using what .....
>
>does it use the hello protocol......does it send it back to the multicast
>address
Update is a specific EIGRP packet type, different from the hello. Router B
sends the Update directly to Router A. Router B learned Router A's address
from an EIGRP hello that Router A sent to the multicast address. Router B
picked up Router A's address from that packet (from the source IP address
in the IP header.)
I know I should spend more time to make this comprehensible, do an ASCII
diagram, print out the Sniffer trace, etc., but I'm kind of busy now....
But if you search the archives, you will find lots of details. Paul (I
can't remember his last name? He's a technical instructor with Mentor, I
believe) even posted some EIGRP sniffer traces at one point.
Also, Doyle's Routing TCP/IP is always helpful.
Priscilla
>is there something in the packet format to recognise on router from another
>if were using the multicast address ??????
>
>if you could just point me in the right direction...i would be most
>gratefull
>
>
>steve
>
> >From: "Priscilla Oppenheimer"
> >Reply-To: "Priscilla Oppenheimer"
> >To: [EMAIL PROTECTED]
> >Subject: Re: Soap Box: EIGRP and IGRP network discovery [7:11273]
> >Date: Mon, 9 Jul 2001 17:26:05 -0400
> >
> >And one other tidbit:
> >
> >EIGRP implements poison reverse.
> >
> >I did some sniffing and here's what I saw:
> >
> >Router A boots and sends hellos to 224.0.0.10
> >Router B boots and sends hellos to 224.0.0.10
> >Router B sends update directly to Router A specifying 4 networks Router B
> >can get to
> >Router A ACKS
> >Router A sends update saying that the 4 networks are unreachable, delay =
> >FFFFFFFF
> >Router B ACKS
> >Router A sends update directly to Router B specifying 1 network Router A
> >can get to
> >Router B ACKS
> >Router B sends update saying that the network is unreachable, delay =
> >FFFFFFFF
> >Router A ACKS
> >
> >Priscilla
> >
> >
> >At 04:40 PM 7/9/01, Patrick Ramsey wrote:
> > >Some additional info on eigrp packets: (from notes after taking the
> >routing
> > >class)
> > >
> > >1,hello: multicast 224.0.0.10 > every 5 seconds or 60 secs on t1 or less
> > >2,update: the actual info received for routing
> > >3,query: the packet sent out to request and update
> > >4,reply:answer to query
> > >5,ack:reliable packet received
> > >
> > >2-4 are connection based, whereas 1 and 5 are not.
> > >
> > >Just a tidbit...You pretty much have everything else the class covered.
> > >
> > >-Patrick
> > >
> > > >>> "John Feuerherd" 07/09/01 04:17PM >>>
> > >Thanks for all the replies (Expect for abc),
> > > I do however feel like we have missed the question. I wanted to
> > > know if
> > >IGRP and EIGRP use the same method in discovering networks. Not how or
if
> > >they establish neighbors. I understand that, but that is not how they
> > >discover networks. With OSPF neighbor adjacencies are not how it
> >discovers
> > >networks, it uses LSAs to do that. I have done a lot of reading on this
> >and
> > >this is where I am at now:
> > >
> > >These are the steps:
> > >1) Upon startup, a router uses Hellos to discover neighbors and to
> >identify
> > >itself to neighbors. When a neighbor is discovered, EIGRP will attempt
to
> > >form an adjacency with that neighbor. (This is all done across the
> >multicast
> > >address 224.0.0.10) This information is stored in the neighbor table.
(Ok
> >we
> > >have established neighbor relationships, but no network information has
> >been
> > >exchanged)
> > >NOTE - ABC you said that IGRP uses DV algorithm to establish neighbors,
> >this
> > >is not true. IGRP does not establish neighbors (no neighbor table). A
lot
> >of
> > >talk from someone who can't even get the facts right.
> > >
> > >2) After an adjacency with a neighbor established, the router will
> >receive
> > >updates from its neighbors. The updates will contain all routes known
by
> > >the sending router. (Plus the metrics - same as IGRP +256) It does this
> > >using the Reliable Transport protocol, which ensures guaranteed delivery
> >of
> > >the routing updates. This is the part where I think that question might
> >have
> > >been referring to. Like a DV routing protocol (IGRP and RIP) the
> >neighbors
> > >sends their whole routing table in one shot. This is only done once, and
> > >then only changes are sent after that.
> > >
> > >3) It then goes on to use the DUAL algorithm, which is out of the scope
> >of
> > >my question so I wont bore you with details.
> > >
> > >After my reading I have decided that there are some similarities on how
> >both
> > >IGRP and EIGRP discover networks, but I have concluded that they are not
> >the
> > >same. Let me know what you think.
> > >
> > >One last note - ABC before you go attacking someone else's knowledge
> >level
> > >with out even knowing what they know, maybe you should take a long look
> >at
> > >your own ignorance. Sure I don't know everything, and I KNOW that I
don't
> > >know enough to be a CCIE (hence the comment "studying for my CCIE"), but
> > >that of course is why I am posting questions on this board. So instead
of
> > >creating a negative atmosphere on the board, why don't you try helping,
> >or
> > >just get off all together. Just a though*.
> > >
> > >Thanks again everyone for your replies!
> > >JF
> >________________________
> >
> >Priscilla Oppenheimer
> >http://www.priscilla.com
>_________________________________________________________________________
>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.
________________________
Priscilla Oppenheimer
http://www.priscilla.com
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