From: Nigel Taylor (nigel_taylor@xxxxxxxxxxx)
Date: Wed Jan 10 2001 - 13:20:29 GMT-3
Craig,
Firstly, all protocols that allow for redistribution have
default metrics to which external routes are identified. For ex...
1 - OSPF assigns the metric of 20 as you pointed out earlier and also
identifies external routes using the default External type 2(E2) when no
specific type is used.
2 - EIGRP of course stands out above most as the protocol has a totally
separate AD of 170 assigned to external routes. Although there are default
values given to the BW, DLY,REL,LOAD,and MTU variables the AD of 170 would
automatically tag these routes as external to the routing domain.
3 - ISIS being much the same as OSPF it too defaults to the level-2 on any
routes redistributed. Of course what must also be noted is that in basic
ISIS configuration cisco defaults to L!/L2 so currently in this scenario
all the ISIS routers are L1/L2.
Before migrating to various level types I was hoping to figure out what that
specific router represents. Off to see if this happens in frame relay....
Also, why do you believe there's no need to summarize..?
In large networks this would be "good practice" smaller routing tables which
means I should be able to do it here.
Trying to tie up this part of my studying on this topic soon...
Thoughts..
Nigel..
----- Original Message -----
From: Thounda Craig, Jr. <tcraig@network-data.com>
To: 'Nigel Taylor' <nigel_taylor@hotmail.com>
Sent: Wednesday, January 10, 2001 9:41 AM
Subject: RE: ISIS and OSPF redistribution Weirdness - Update
> Look at Jeff Doyle's book "Routing TCP/IP" (p. 730-732)
> It explains how to redistribute IS-IS into other protocols.
>
> Note: You need to specific "level" with the "summary" and "redistribute"
> command.
> No need to summarize as the book will probably provide more info.
>
> I think this explains your question.
>
> -----Original Message-----
> From: Nigel Taylor [mailto:nigel_taylor@hotmail.com]
> Sent: Wednesday, January 10, 2001 7:50 AM
> To: tcraig@network-data.com
> Subject: Re: ISIS and OSPF redistribution Weirdness - Update
>
> Craig,
> If you look again at the example I do have a metric defined
for
> the ISIS routes being redistributed into the OSPF domain. The problem
that
> I'm looking at is the advertisement of the summarized router into the ISIS
> domain that shows up in the ASBR as;
>
> i su 172.16.0.0/16 [115/30] via 0.0.0.0, Null0
>
> Thoughts....
>
> Nigel..
>
>
>
> ----- Original Message -----
> From: Thounda Craig, Jr. <tcraig@network-data.com>
> To: 'Nigel Taylor' <nigel_taylor@hotmail.com>
> Sent: Wednesday, January 10, 2001 7:39 AM
> Subject: RE: ISIS and OSPF redistribution Weirdness - Update
>
>
> > If I understand your question correctly, you are getting a metric of 20
> b/c
> > that's the default for OSPF when the administrator does not assign one
> > during the redistribution process.
> >
> > brgds,
> > Craig
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Nigel Taylor
> > Sent: Wednesday, January 10, 2001 7:26 AM
> > To: Cisco Group Study; CCIE_Lab Group Study
> > Subject: ISIS and OSPF redistribution Weirdness - Update
> >
> > Hi All,
> > I was working with redistribution between OSPF and IS-IS domains and got
=
> > this=20
> > route in the table and wondered if anyone have seen this and could =
> > explain. I'm=20
> > using the example from Slattery/Burton pg. 297 (ex. #10). I've replace =
> > the EIGRP=20
> > process with Isis and in summarizing the ospf routes into isis I get the
=
> > following=20
> > route in the RIB of the router doing the redistribution/summarization...
> >
> > Relevant configs...on the router performing redistribution.
> >
> > !
> > router ospf 200
> > log-adjacency-changes
> > summary-address 182.18.0.0 255.255.0.0
> > redistribute isis metric 300 metric-type 1 subnets
> > network 172.16.253.4 0.0.0.3 area 0
> > network 172.16.254.0 0.0.0.255 area 0
> > distribute-list 4 out
> > !
> > router isis=20
> > summary-address 172.16.0.0 255.255.0.0 =20
> > redistribute ospf 200 =20
> > net 48.0001.0000.0000.0001.00
> >
> >
> >
> > r2_01#sh ip ro
> > 172.16.0.0/16 is variably subnetted, 9 subnets, 5 masks
> > O IA 172.16.2.252/30 [110/139] via 172.16.254.1, 02:35:35, Ethernet0
> > C 172.16.254.0/24 is directly connected, Ethernet0
> > C 172.16.253.4/30 is directly connected, Loopback0
> > O 172.16.253.9/32 [110/11] via 172.16.254.1, 02:35:35, Ethernet0
> > O IA 172.16.2.32/27 [110/144] via 172.16.254.1, 02:35:35, Ethernet0
> > O IA 172.16.2.4/30 [110/202] via 172.16.254.1, 02:35:35, Ethernet0
> > i su 172.16.0.0/16 [115/30] via 0.0.0.0, Null0
> > O IA 172.16.1.0/24 [110/74] via 172.16.254.1, 02:35:36, Ethernet0
> > O IA 172.16.2.0/24 [110/138] via 172.16.254.1, 02:35:36, Ethernet0
> > 182.18.0.0/16 is variably subnetted, 6 subnets, 2 masks
> > i L1 182.18.4.0/24 [115/20] via 182.18.1.1, Serial1
> > i L1 182.18.5.0/24 [115/20] via 182.18.2.2, Serial0
> > O 182.18.0.0/16 is a summary, 02:21:02, Null0
> > C 182.18.1.0/24 is directly connected, Serial1
> > C 182.18.2.0/24 is directly connected, Serial0
> > i L1 182.18.3.0/24 [115/20] via 182.18.2.2, Serial0
> > [115/20] via 182.18.1.1, Serial1
> >
> >
> > Connected ISIS router which sees the summarized route...
> >
> > r4_02c#sh ip ro
> > Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
> > D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area=20
> > N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> > E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> > i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
> > U - per-user static route, o - ODR
> >
> > Gateway of last resort is not set
> >
> > i L2 172.16.0.0/16 [115/40] via 182.18.1.2, Serial0
> > 182.18.0.0/16 is variably subnetted, 6 subnets, 2 masks
> > C 182.18.4.0/24 is directly connected, TokenRing0
> > i L1 182.18.5.0/24 [115/20] via 182.18.3.1, Serial1
> > i L2 182.18.0.0/16 [115/40] via 182.18.1.2, Serial0
> > C 182.18.1.0/24 is directly connected, Serial0
> > i L1 182.18.2.0/24 [115/20] via 182.18.3.1, Serial1
> > [115/20] via 182.18.1.2, Serial0
> > C 182.18.3.0/24 is directly connected, Serial
> >
> >
> >
> > i su 172.16.0.0/16 [115/30] via 0.0.0.0, Null0
> >
> > I'm thinking that this route is being suppressed but on the connected =
> > isis=20
> > routers within it's routing domain I get this summarized route to the =
> > ospf networks.=20
> > What does the "su" represent in the table. And if this is being =
> > suppressed why is=20
> > it showing up in the RIB at all. I know BGP allows the suppression of =
> > routes and=20
> > was unaware that IGP's did this as well. Is this only specific to =
> > isis..?
> > Has anyone encountered this and knows what it means. Off to check the =
> > RFC's.
> > =20
> > Nigel..
> >
> >
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