RE: ip split horizon letting ospf routes slip through

From: Gupta, Gopal (NWCC) (gopal.gupta@hp.com)
Date: Thu Nov 08 2007 - 06:19:03 ART

Hi Shiran,

Thanks for the reply, could you please throw some light , is there one
and only one way to filter routes in the same area i.e. configuring
locally on every router to filter routes from entering into the routing
table ?? or can we configure the advertising router to stop sending the
updates or LSAs to its neighbor ??

Regards,
Gops

From: shiran guez [mailto:shiranp3@gmail.com]
Sent: Thursday, November 08, 2007 14:42
To: Gupta, Gopal (NWCC)
Cc: Ahsan Mohiuddin; ccielab@groupstudy.com
Subject: Re: ip split horizon letting ospf routes slip through

Gops

Nothing is blocking LSA in OSPF area accept link down as it is Link
State Protocol and his whole concept is one DB same to all neighbors.

Distance is locally significant and not advertised! so what you will do
is only block your self from using the route but not block the LSA from
going to your neighbors.

In an AREA all NEIGHBORS SHARE THE SAME DB.

On Nov 8, 2007 10:50 AM, Gupta, Gopal (NWCC) <gopal.gupta@hp.com> wrote:

        Hi Ahsan,

        As far as I know split horizon cannot block OSPF LSAs.
        What you can do is filter routes on R3 using Distance 255 for
the route
        coming from R5.

        HTH
        Gops

        -----Original Message-----
        From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf Of
        Ahsan Mohiuddin
        Sent: Thursday, November 08, 2007 14:01
        To: ccielab@groupstudy.com
        Subject: ip split horizon letting ospf routes slip through
        Importance: Low

        hello group,

        i have routers R1, R3 (FR spokes) connected to Hub R5. R1 is
advertising
        route 155.2.146.0 <http://155.2.146.0/> to R5, but I do not
want R5 to send this update to R3.
        So, I have configured "ip split-horion" under R5's physical
interface
        (subinterfaces not used). But it seems R3 is still learning the
route
        from R1:

        O 155.2.146.0 <http://155.2.146.0/> [110/65] via
155.2.13.1 <http://155.2.13.1/> , 00:10:27, Serial1/0
                           [110/65] via 155.2.0.1 <http://155.2.0.1/> ,
00:10:27, Serial1/1

        Config of R5

        interface Serial1/0
         ip address 155.2.0.5 <http://155.2.0.5/> 255.255.255.0
<http://255.255.255.0/>
         encapsulation frame-relay
         ip split-horizon
         ip ospf priority 2
         frame-relay map ip 155.2.0.1 <http://155.2.0.1/> 501
         frame-relay map ip 155.2.0.3 <http://155.2.0.3/> 503
         frame-relay map ip 155.2.0.4 <http://155.2.0.4/> 504
        end

        Config of R3

        interface Serial1/1
         ip address 155.2.0.3 <http://155.2.0.3/> 255.255.255.0
<http://255.255.255.0/>
         encapsulation frame-relay
         ip ospf priority 0
         serial restart-delay 0
         no dce-terminal-timing-enable
         frame-relay map ip 155.2.0.5 <http://155.2.0.5/> 305
        end

        Config of R1

        interface Serial1/0
         ip address 155.2.0.1 <http://155.2.0.1/> 255.255.255.0
<http://255.255.255.0/>
         encapsulation frame-relay
         ip ospf priority 0
         serial restart-delay 0
         no dce-terminal-timing-enable
         frame-relay map ip 155.2.0.5 <http://155.2.0.5/> 105
        end

        Any idea what i am doing wrong here?

        Thanks in adv
        -Ahsan

         __________________________________________________
        Do You Yahoo!?
        Tired of spam? Yahoo! Mail has the best spam protection around
        http://mail.yahoo.com <http://mail.yahoo.com/>

This archive was generated by hypermail 2.1.4 : Sat Dec 01 2007 - 06:37:28 ART