Comments on: OSPF Prefix Filtering using Forwarding Address http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/ Helping you become a Cisco Certified Internetwork Expert Tue, 07 Feb 2012 02:21:38 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Understanding Third-Party Next-Hop | CCIE Blog http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-133728 Understanding Third-Party Next-Hop | CCIE Blog Thu, 02 Sep 2010 13:34:28 +0000 http://blog.ine.com/?p=2737#comment-133728 [...] Routing Problem with OSPF Forwarding Address OSPF Prefix Filtering Using Forwarding Address Tags: bgp, CCDE, ccie, eigrp, ospf, rip, third-party next-hop Download this page as a [...] [...] Routing Problem with OSPF Forwarding Address OSPF Prefix Filtering Using Forwarding Address Tags: bgp, CCDE, ccie, eigrp, ospf, rip, third-party next-hop Download this page as a [...]

]]> By: Olga http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-101388 Olga Tue, 23 Mar 2010 08:47:40 +0000 http://blog.ine.com/?p=2737#comment-101388 >>However, Cisco’s implementation is OK if the prefix is accessible via any non-OSPF protocol, e.g. BGP It could be IOS version, because I cleary remember how we had problems while migrating to IS-IS and have some prefixes in IS-IS, some in OSPF - some E2 was not in RIB because FA was not reachable (but it was known via IS-IS). >>However, Cisco’s implementation is OK if the prefix is accessible via any non-OSPF protocol, e.g. BGP

It could be IOS version, because I cleary remember how we had problems while migrating to IS-IS and have some prefixes in IS-IS, some in OSPF – some E2 was not in RIB because FA was not reachable (but it was known via IS-IS).

]]> By: Net_OG http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-81039 Net_OG Wed, 25 Nov 2009 03:22:46 +0000 http://blog.ine.com/?p=2737#comment-81039 Petr, no worries I had the link thanks to google. Just being a good INE-Citizen and letting you guys know... thanks for the great post. Some of these posts were way to in depth for me but now they are really making a lot of sense. Keep up the good work. Petr,

no worries I had the link thanks to google.

Just being a good INE-Citizen and letting you guys know…
thanks for the great post. Some of these posts were way to in depth for me but now they are really making a lot of sense. Keep up the good work.

]]> By: Petr Lapukhov, CCIE #16379 http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-80954 Petr Lapukhov, CCIE #16379 Tue, 24 Nov 2009 15:58:00 +0000 http://blog.ine.com/?p=2737#comment-80954 @NET_OG Did not post your comment just as you asked :) Sorry about the broken link, there was a leading space (%20) in the URL. @NET_OG

Did not post your comment just as you asked :) Sorry about the broken link, there was a leading space (%20) in the URL.

]]> By: Bobby Hockensmith http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-79352 Bobby Hockensmith Tue, 17 Nov 2009 03:22:54 +0000 http://blog.ine.com/?p=2737#comment-79352 Can anybody explain why a Type-4 is inserted into a non-backbone area by an ABR when the type-5 has a non-zero forwarding address. I know IOS does this -- not sure about Juniper -- and there is nothing in the RFC to do this when it is not needed. I could be wrong, but I am positiive the Type-4 is not used. The routers in that area will use the LSA 3 to do a lookup for the forwarding-address to determine best path and metric and from there use the LSA 1 for the ABR that inserted the LSA 3. Can anybody explain why a Type-4 is inserted into a non-backbone area by an ABR when the type-5 has a non-zero forwarding address. I know IOS does this — not sure about Juniper — and there is nothing in the RFC to do this when it is not needed. I could be wrong, but I am positiive the Type-4 is not used. The routers in that area will use the LSA 3 to do a lookup for the forwarding-address to determine best path and metric and from there use the LSA 1 for the ABR that inserted the LSA 3.

]]> By: Eamonn McGonigle http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-79302 Eamonn McGonigle Mon, 16 Nov 2009 20:55:52 +0000 http://blog.ine.com/?p=2737#comment-79302 Hi Petr, Thanks for an interesting article. May I point out a small error in your diagram ? The network connected to R1:Serial0/0 is labelled as OSPF Area 168 but should be labelled as Area 0 Hi Petr,

Thanks for an interesting article. May I point out a small error in your diagram ? The network connected to R1:Serial0/0 is labelled as OSPF Area 168 but should be labelled as Area 0

]]> By: IPv6Freely http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-78887 IPv6Freely Sat, 14 Nov 2009 20:48:45 +0000 http://blog.ine.com/?p=2737#comment-78887 Thank god nothing this crazy would ever be on the lab... still neat though! Thank god nothing this crazy would ever be on the lab… still neat though!

]]> By: Deepak Arora http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-78738 Deepak Arora Fri, 13 Nov 2009 23:13:15 +0000 http://blog.ine.com/?p=2737#comment-78738 Hi Petr, Can you please spend some time to writeup an article on OSPF Incremental SPF (ISPF), SPF throttling, pacing timers, I know it's only matter of few command but understanding it's behavior with some practical example will be a great help from you. Thanks! Deepak Arora Hi Petr,

Can you please spend some time to writeup an article on OSPF Incremental SPF (ISPF), SPF throttling, pacing timers, I know it’s only matter of few command but understanding it’s behavior with some practical example will be a great help from you.

Thanks!
Deepak Arora

]]> By: Petr Lapukhov, CCIE #16379 http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-78698 Petr Lapukhov, CCIE #16379 Fri, 13 Nov 2009 19:46:35 +0000 http://blog.ine.com/?p=2737#comment-78698 @Ivan, heh, what's really is "fun" is that Cisco violates the RFC for FA checks. Per the standard the prefix must be either OSPF internal or inter-area route. However, Cisco's implementation is OK if the prefix is accessible via any non-OSPF protocol, e.g. BGP. Then again, no one is oblidged to follow the standard, even if it makes sense ;) @Ivan,

heh, what’s really is “fun” is that Cisco violates the RFC for FA checks. Per the standard the prefix must be either OSPF internal or inter-area route. However, Cisco’s implementation is OK if the prefix is accessible via any non-OSPF protocol, e.g. BGP. Then again, no one is oblidged to follow the standard, even if it makes sense ;)

]]> By: IK http://blog.ine.com/2009/11/13/ospf-prefix-filtering-using-forwarding-address/#comment-78690 IK Fri, 13 Nov 2009 17:54:06 +0000 http://blog.ine.com/?p=2737#comment-78690 great research, thank you Petr! great research, thank you Petr!

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