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<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=374043913-20022003>Wayne
is correct in that there are uses for filtering LSA information, that, while in
the graph theoretical sense are contrary to link state design, are still very
in-tune with IP network design. A perfect example is a stub-host.
There are oher ways to do this, but this is one example. Another may be a
firewall running gated that you may wish to hide some information from/to.
And finally. type 5 and 7 LSAs should be filterable as they are "pathed" based
on distance vector info.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=374043913-20022003></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=374043913-20022003>Again,
YMMV and loops can be common in this environment. </SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=374043913-20022003></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=374043913-20022003>-c</SPAN></FONT></DIV>
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<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma size=2>-----Original Message-----<BR><B>From:</B> Wayne (juniper
nsp) [mailto:wg-jnpr-nsp@wgustavus.com] <BR><B>Sent:</B> Tuesday, February 18,
2003 12:07 PM<BR><B>To:</B> Elliott, Andrew; 'Ben Buxton'; 'Ajay Bhardwaj';
juniper-nsp@puck.nether.net<BR><B>Subject:</B> Re: [j-nsp] Filtering OSPF
routes<BR><BR></FONT></DIV>
<DIV><FONT size=2>
<P>Ok,</P>
<P>On the off chance that it wasn't clear in my original post when I said
"contrary to the design of OSPF (or any link state</P>
<P>protocol)", I am NOT advocating anyone doing this. I am simply pointing out
that Cisco IOS provides a knob to do what he described.</P>
<P>- Wayne</P>
<P> </P></FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=AElliott@xo.com href="mailto:AElliott@xo.com">Elliott, Andrew</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=wg-jnpr-nsp@wgustavus.com
href="mailto:wg-jnpr-nsp@wgustavus.com">'Wayne (juniper nsp)'</A> ; <A
title=B.Buxton@Planettechnologies.nl
href="mailto:B.Buxton@Planettechnologies.nl">'Ben Buxton'</A> ; <A
title=ajay.bhardwaj@in.spectranet.com
href="mailto:ajay.bhardwaj@in.spectranet.com">'Ajay Bhardwaj'</A> ; <A
title=juniper-nsp@puck.nether.net
href="mailto:'juniper-nsp@puck.nether.net'">'juniper-nsp@puck.nether.net'</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, February 18, 2003 10:26
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: [j-nsp] Filtering OSPF
routes</DIV>
<DIV><BR></DIV>
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<P><FONT size=2>Wayne, </FONT><BR><FONT size=2> </FONT> <BR><FONT
size=2>I have seen this in action, and it is ugly.</FONT> <BR><FONT
size=2> </FONT> <BR><FONT size=2>I recently had to work on a Cisco
network where all routers were in</FONT> <BR><FONT size=2>one of two areas,
and they were using the distribute-lists to only</FONT> <BR><FONT size=2>use
the 0/0 LSA. This created many routing loops, and I asked the</FONT>
<BR><FONT size=2>"designer" what they were thinking, and basically got the
cold</FONT> <BR><FONT size=2>shoulder. I couldn't understand why
someone would want to use OSPF</FONT> <BR><FONT size=2>and then deliberately
break it in that manner.</FONT> <BR><FONT size=2> </FONT> <BR><FONT
size=2>Has anyone on this list ever seen a good reason to filter
LSAs?</FONT> <BR><FONT size=2> </FONT> <BR><FONT size=2>-
-andrew</FONT> </P>
<P><FONT size=2>- -----Original Message-----</FONT> <BR><FONT size=2>From:
Wayne (juniper nsp) [<A
href="mailto:wg-jnpr-nsp@wgustavus.com">mailto:wg-jnpr-nsp@wgustavus.com</A>]
</FONT><BR><FONT size=2>Sent: Saturday, February 15, 2003 11:43 PM</FONT>
<BR><FONT size=2>To: Ben Buxton; Ajay Bhardwaj;
juniper-nsp@puck.nether.net</FONT> <BR><FONT size=2>Subject: Re: [j-nsp]
Filtering OSPF routes</FONT> </P><BR><BR>
<P><FONT size=2>Actually, if you are running a sufficiently high enough
version of</FONT> <BR><FONT size=2>IOS (e.g. 12.0S), the 7200 can filter
some LSAs. It depends on your</FONT> <BR><FONT size=2>exact scenario
if this will accomplish what you are trying to do. It</FONT> <BR><FONT
size=2>does tend to go contrary to the design of OSPF (or any link
state</FONT> <BR><FONT size=2>protocol), but I suppose enough people wanted
the knob, so they got</FONT> <BR><FONT size=2>it.</FONT> <BR><FONT
size=2> </FONT> <BR><FONT size=2>Not sure if JUNOS has a similar
knob.</FONT> <BR><FONT size=2> </FONT> <BR><FONT size=2>- - Wayne
</FONT></P>
<P><FONT size=2>- ----- Original Message ----- </FONT><BR><FONT size=2>From:
Ben Buxton </FONT><BR><FONT size=2>To: Ajay Bhardwaj ;
juniper-nsp@puck.nether.net </FONT><BR><FONT size=2>Sent: Monday, February
10, 2003 4:18 AM</FONT> <BR><FONT size=2>Subject: RE: [j-nsp] Filtering OSPF
routes</FONT> </P>
<P><FONT size=2></FONT><BR><FONT size=2>You cannot filter OSPF. This would
break the requirement that all</FONT> <BR><FONT size=2>routers have</FONT>
<BR><FONT size=2>the same link state view.</FONT> <BR><FONT size=2>This is
true for both Junos and IOS.</FONT> <BR><FONT size=2> </FONT> <BR><FONT
size=2>BB</FONT> </P>
<P><FONT size=2>- -----Original Message-----</FONT> <BR><FONT size=2>From:
Ajay Bhardwaj [<A
href="mailto:ajay.bhardwaj@in.spectranet.com">mailto:ajay.bhardwaj@in.spectranet.com</A>]
</FONT><BR><FONT size=2>Sent: Monday, 10 February 2003 08:39</FONT>
<BR><FONT size=2>To: juniper-nsp@puck.nether.net</FONT> <BR><FONT
size=2>Subject: [j-nsp] Filtering OSPF routes</FONT> </P><BR>
<P><FONT size=2>Hi all,</FONT> <BR><FONT size=2> </FONT> <BR><FONT
size=2>We have cisco 7200 router and M-5 router both running ospf and
part</FONT> <BR><FONT size=2>of area 10.</FONT> <BR><FONT
size=2> </FONT> <BR><FONT size=2>I want to deny few routes which are
flowing trough ospf from 7200 to</FONT> <BR><FONT size=2>m5 either at 7200
side or m5 side. Pls if anyone have any solution to</FONT> <BR><FONT
size=2>this would be gr8 help for me.</FONT> <BR><FONT size=2> </FONT>
<BR><FONT size=2>Ajay Bhardwaj</FONT> </P><BR><BR>
<P><FONT size=2> _____ </FONT></P><BR><BR><BR>
<P><FONT size=2>_______________________________________________</FONT>
<BR><FONT size=2>juniper-nsp mailing list juniper-nsp@puck.nether.net</FONT>
<BR><FONT size=2><A
href="http://puck.nether.net/mailman/listinfo/juniper-nsp"
target=_blank>http://puck.nether.net/mailman/listinfo/juniper-nsp</A></FONT>
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