From: Lee Donald (Lee.Donald@t-systems.co.uk)
Date: Sun Sep 11 2005 - 10:17:29 GMT-3
Tim,
That's great. I've just tested it and it works using the router-id instead
of the source ip, like in other igp's. Typical Cisco, to implement it
differently.
I thought it didn't work for OSPF, thanks a lot.
What do you mean the protocol specific form? Class ?
Regards
Lee.
-----Original Message-----
From: Tim [mailto:ccie2be@nyc.rr.com]
Sent: Sunday, September 11, 2005 4:57 PM
To: 'Venkataramanaiah.R'; 'Lee Donald'
Cc: 'FCO.JAVIER TOME MORAN'; ccielab@groupstudy.com
Subject: RE: OSPF distance command
Venkat,
I think you mis-spoke.
OSPF IS a Link-State protocol, not a distance vector protocol.
And, when the distance command is used with ospf, the ip address MUST
reference the router id of the router from which the local router is
learning the routes.
As a side note, all ccie candidates should know that ospf (and most others
IGP's) support 2 forms of the distance command.
One form is the "generic" form being used in this example which can be used
with any IGP. The other form is the protocol specific form.
Personally, I like to think of the "generic" form as the retail model of the
command because with this form of the command, you can use an acl to specify
very specifically to which routes the command applies.
The protocol specific form I think of as the wholesale form of the command
because instead of using an acl to specify which routes the new AD applies
to, you specify which "class" of routes the command where "class" refers to
a whole category of routes such as internal or external.
When the same result can be achieved with either form of the command, I
prefer using the protocol specific form for a couple of reasons.
With the IGP specific form of the command, you don't need to be concerned
with whether the ip address references the interface address or the
router-id which means there's less to remember and there's less chance of
error.
Also, by not needing to create an acl, you avoid the highly error prone
configuration task of acl creation. When using an acl, all sorts of
mistakes are possible and easy to make from omitting a needed route, to
using the wrong subnet mask and so on.
But, sometimes it's impossible to avoid using the generic distance command
and therefore it's important to know what to lookout for and when this form
can't be avoided.
HTH, Tim
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Venkataramanaiah.R
Sent: Sunday, September 11, 2005 4:43 AM
To: Lee Donald
Cc: FCO.JAVIER TOME MORAN; ccielab@groupstudy.com
Subject: Re: OSPF distance command
Hi,
* distance 171 0.0.0.0 <http://0.0.0.0>
255.255.255.255<http://255.255.255.255>1
Use a permit all wild card, while modifying the distance for routes under
OSPF. This will cover all the router ids in the area and hence will cover
all the routes mentioned in access-list 1 although the originator for those
routes might be different within the area. See JD-I pg 792
OSPF being a distance Vector protocol, the updates could be anyone in the
area, so you cannot filter a route specifically from a neighbor. Well when
you want to use the distance command in OSPF, apply to all the guys.
Please correct if i am wrong
Thanks
-Venkat
On 9/11/05, Lee Donald <Lee.Donald@t-systems.co.uk> wrote:
>
> The distance command does not work this way for OSPF. Don't ask me why but
> for RIP, and I think EIGRP, the config you have would work but not for
> OSPF.
>
> Regards
>
> Lee.
>
>
>
> -----Original Message-----
> From: FCO.JAVIER TOME MORAN [mailto:fjtm@tid.es]
> Sent: Sunday, September 11, 2005 10:42 AM
> To: ccielab@groupstudy.com
> Subject: OSPF distance command
>
> Hi all,
>
> Not sure about how distance command works in OSPF. I am working in a
> frame-relay hub an spoke environment with three routers R1, R2, and R5
> (R5 as the hub). OSPF network-type has been set as point-to-multipoint
> non-broadcast, and neighbor cost has been modified to use one of the
> neighbors (R1) as the preferred path...
>
> Here are my configs...
>
>
> On R5...
> ********
>
> router ospf 1
> router-id 150.1.5.5 <http://150.1.5.5>
> log-adjacency-changes
> redistribute eigrp 10 metric-type 1 subnets
> network 150.1.5.5 <http://150.1.5.5> 0.0.0.0 <http://0.0.0.0> area 0
> network 173.1.125.5 <http://173.1.125.5> 0.0.0.0 <http://0.0.0.0> area 0
> <--- This is ip addressing on
> frame-relay
> neighbor 173.1.125.1 <http://173.1.125.1> cost 130
> neighbor 173.1.125.2 <http://173.1.125.2> cost 1562
> distance 109 173.1.125.2 <http://173.1.125.2> 0.0.0.0
<http://0.0.0.0>BGP_DLSW
>
>
> ip access-list standard BGP_DLSW
> permit 150.1.2.0 <http://150.1.2.0> 0.0.0.255 <http://0.0.0.255>
>
>
> On R1...
> ********
>
> router ospf 1
> router-id 150.1.1.1 <http://150.1.1.1>
> log-adjacency-changes
> network 150.1.1.1 <http://150.1.1.1> 0.0.0.0 <http://0.0.0.0> area 0
> network 173.1.13.1 <http://173.1.13.1> 0.0.0.0 <http://0.0.0.0> area 0
> network 173.1.125.1 <http://173.1.125.1> 0.0.0.0 <http://0.0.0.0> area 0
> network 173.1.137.1 <http://173.1.137.1> 0.0.0.0 <http://0.0.0.0> area 137
>
> On R2...
> ********
>
> router ospf 1
> router-id 150.1.2.2 <http://150.1.2.2>
> log-adjacency-changes
> area 23 nssa default-information-originate metric 100
> network 150.1.2.2 <http://150.1.2.2> 0.0.0.0 <http://0.0.0.0> area 0
> network 173.1.23.2 <http://173.1.23.2> 0.0.0.0 <http://0.0.0.0> area 23
> network 173.1.32.2 <http://173.1.32.2> 0.0.0.0 <http://0.0.0.0> area 0
> network 173.1.125.2 <http://173.1.125.2> 0.0.0.0 <http://0.0.0.0> area 0
> distance 109 173.1.125.5 <http://173.1.125.5> 0.0.0.0
<http://0.0.0.0>BGP_DLSW
>
> ip access-list standard BGP_DLSW
> permit 150.1.5.0 <http://150.1.5.0> 0.0.0.255 <http://0.0.0.255>
>
>
>
>
> My point is to make R2 (173.1.125.2 <http://173.1.125.2>) as the next-hop
> to R2 loopback
> address on R5, and R5 (173.1.125.5 <http://173.1.125.5>) as the next-hop
> to R5 loopback
> address on R2. This way I would force BGP and DLSW session to be
> stablished over the low speed frame-relay circuit between R2 and R5,
> overriding the cost of the circuit.
> Nontheless, I get no change on the routing table of R5 and R2.
>
> I have also tried using router-id as the source of the routing
> information in the distance command (i.e "distance 109
150.1.2.2<http://150.1.2.2>
> 0.0.0.0 <http://0.0.0.0> BGP_DLSW" on router R5 and so on). With this
> configuration I
> get the AD of the route change, but the next hop still points to R1.
>
> I guess I have some missunderstanding on the technology. Could anyone
> put some light on the issue?...
>
> Thank you in advance
>
> JT
>
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