Steve,
~you said: r1 and r3 to get to the ethernet sement would have to go thru
RIP.
~my reply:Well the wording is kindof wierd, but the way I think of it is r1
will receive a route for the ethernet segment from r5 via RIP and from r2
via OSPF and the same on r3 it will receive a route to the ethernet segment
from r4 via RIP and from r2 via OSPF. I did say on r1 and r3 full
redistribution was taking place (OSPF into RIP & RIP into OSPF).
So what is happenning is r1 and r3 are receiving RIP routes to the /16
network from the ethernet segment and they are also receiving OSPF External
routes to the /16 ethernet segment. The reason I mention the mask is because
one is not more specific than the other so administrative distance is next
distinction for placement in the routing table.
The rest of the questions I think are questioning concern how redistribution
works. I'll try help, but Jeff Doyle will do a much better job since there
were alot of other variables that played into this scenario (like a
classless routing protocol into a classfull routing protocol)
r1 and r3 will receive RIP routes and OSPF routes since one of their
serial's are in the OSPF process and the other is in the RIP process, it is
up to this router to determine which route goes into it's routing table if
it receives 2 routes to a certain destination.
The redistribution for lets say RIP into OSPF -says if you receive a route
from RIP send these routes along with your other regular OSPF updates out of
the designated OSPF interfaces and give them this metric when you send them.
The redistribution doesn't effect how the redistributing router will
determine it's best route, it just controls how this router sends routing
updates.
~I said: What ends up happening is one of the ASBR's uses the OSPF route and
the other one uses the RIP route, dependancy upon which one comes to full
first will use the RIP route, and the other one will use the OSPF route.
~you said: THERE is no ospf route......R4 and R5 are using RIP ....you can`t
get to the ethernet segment via ospf only rip .....
you can go VIA a Re-distributed route ....but it`s a RIP re-distributed
route not ospf...what i mean is the route to r4 and r5 is re-dis into ospf
via rip .... r2 wants to get to the ether-link ... it uses the re-dist rip
route andvertised via ospf...yes it`s an ospf route BUT it came from RIP..so
what do you mean ...?????
r2 wants to get to the ether-link ... it uses the re-dist rip route
andvertised via ospf... yes it`s an ospf route BUT it came from RIP
~my reply: I was talking about r1 and r3, I am considering them to be ASBR's
(because they have a connection outside of the OSPF process -I'm not sure of
the exact RFC terminology, but I believe these would be considered ASBR's)
So thinking about r1 or r3 they can get to this ethernet segment via either
a RIP route or an external OSPF route. (I call the redistributed RIP route
an OSPF External route once it's in the OSPF process). Yea it originally
came from RIP, but r2 just know's it's an external OSPF route r2 doesn't
know it used to be a RIP route it just received it from r1 and r3 via OSPF.
r2 is not running RIP.
I've tried to explain as far as my knowledge level goes, but I'm not to sure
if I fully understand your questions , or maybe I am overlooking something?
Could you try asking the questions more directly or differently if I haven't
helped?
>>>Brian
>From: "Stephen Skinner"
>Reply-To: [EMAIL PROTECTED]
>To: [EMAIL PROTECTED], [EMAIL PROTECTED]
>Subject: Re: OSPF scenario [7:7605]
>Date: Fri, 08 Jun 2001 09:29:12 -0000
>
>Hi
>i don`t mean to be rude but ,for r1 and r3 to get to the ethernet
>segment,you will have to go throught rip...??????
>
>
>
>>I had originally thought that both of the ASBR's would choose the OSPF
>>route
>>to the ethernet segment between the 2 routers running only RIP, since the
>>routes are identical in mask length,
>
>
>R4 and R5 are only running rip ...yes.....
>so how do you get to the ethernet segment between them Via an ospf path if
>the are only running RIP???????
>
>the rip path will be advertised as an OSPF E2 path ..yes...
>so there is NO rip path.....there are only OSPF paths...that is what
>re-distribution does right...?????
>
>HELP..... i am confused
>
>
>>What ends up happening is one of the ASBR's uses the OSPF route and the
>>other one uses the RIP route, dependancy upon which one comes to full
>>first
>>will use the RIP route, and the other one will use the OSPF route.
>
>THERE is no ospf route......R4 and R5 are using RIP ....you can`t get to
>the ethernet segment via ospf only rip .....
>
>you can go VIA a Re-distributed route ....but it`s a RIP re-distributed
>route not ospf...
>
>what i mean is
>
>the route to r4 and r5 is re-dis into ospf via rip ....
>r2 wants to get to the ether-link ...
>it uses the re-dist rip route andvertised via ospf...
>
>yes it`s an ospf route BUT it came from RIP..
>
>so what do you mean ...?????
>
>i thought i knew OSPF but you have confused me totally..
>
>if i need help understanding this please help
>
>steve(.............me nogggin`s gone all soft,Guv)
>
>
>
>
>>From: "Brian Lodwick"
>>Reply-To: "Brian Lodwick"
>>To: [EMAIL PROTECTED]
>>Subject: OSPF scenario [7:7605]
>>Date: Thu, 7 Jun 2001 17:17:54 -0400
>>
>>I've come across a wierd OSPF issue in a lab scenario I thought might be
>>fun
>>for everyone to comment on (instead of a bunch of gossip on salaries and
>>brain dumps)
>>
>>The scenario has 5 routers (NLI-lab 7) and the last thing I want to do is
>>upset NLI by divulging their lab scenario so I'll try to briefly go over
>>what I thought was interesting without divulging the whole thing.
>>
>>There are 3 routers running OSPF on the top. 2 of the 3 have OSPF on one
>>serial interface and RIP on the other serial interface -fully
>>redistributing
>>both ways. On the bottom there are 2 routers running RIP on their serial
>>interfaces (which are connected to the RIP serials on the redistributing
>>routers) then those 2 bottom RIP only routers are connected together via
>>an
>>ethernet segment which are both running RIP on the ethernets as well.
>>
>>r1 --- r2 --- r3
>>| |
>>| |
>>r4 --------- r5
>>
>>I believe the two redistributing routers would be considered ASBR's in
>>OSPF.
>>I had originally thought that both of the ASBR's would choose the OSPF
>>route
>>to the ethernet segment between the 2 routers running only RIP, since the
>>routes are identical in mask length, the next thing is to look at the
>>administrative distance. Since OSPF has is lower it should choose the OSPF
>>route, but if they both use the OSPF route you would obviosly create a
>>routing loop, which cannot happen in OSPF since it creates a topological
>>database.
>>What ends up happening is one of the ASBR's uses the OSPF route and the
>>other one uses the RIP route, dependancy upon which one comes to full
>>first
>>will use the RIP route, and the other one will use the OSPF route.
>>It seems OSPF will only allow one external exit point for each outside
>>subnet. But why don't both of the ASBR's choose the RIP routes and equal
>>cost load balance out of the external links as it does internally?
>>I think it's a neat scenario. I really liked it, the overall issue was to
>>learn how to control the routing process to most efficiently route to the
>>destination, but I learned alot about the way OSPF works too.
>>
>> >>>Brian
>>_________________________________________________________________
>>Get your FREE download of MSN Explorer at http://explorer.msn.com
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=7733&t=7605
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
