Oh you're so going to make me lab this up in Juniper :-).
I don't think IOS will bounce, but there's been some time since I
tried changing MTU on an interface with a working adjacency.
-- Marko Milivojevic - CCIE #18427 (SP R&S) Senior CCIE Instructor - IPexpert On Sat, Jan 5, 2013 at 12:46 PM, rakesh madupu <raaki.88_at_gmail.com> wrote: > Hey John, > > I am pretty sure Ospf Bounces in Juniper if we change MTU on an interface, > even 3560's it makes sense to have "ip ospf mtu ignore" or system mtu ignore > to deliberately hold ospf Adj's, I think MTU along with other parameters > must be matched for Ospf to stay up > > Regards > Rakesh M > > > On Sun, Jan 6, 2013 at 12:47 AM, John Neiberger <jneiberger_at_gmail.com> > wrote: >> >> I ran into that ISIS MTU issue at work this week on a production link. I >> needed to increase the MTU on a link that was running OSPF and ISIS. When I >> changed the MTU on one side, ISIS got a little angry with me until I >> increased the MTU on the other side. The reason is that ISIS has a Padding >> TLV wherein it pads its hello packets to the full MTU size. That's how it >> insures that there is no mismatch. If one side has a larger MTU, that packet >> will be dropped when it reaches the other side. Once I fixed both ends, ISIS >> was happy again. >> >> Interestingly, OSPF also bounced, which I thought was odd. In IOS, if you >> already have an adjacency and routing is stable, you can change the MTU >> without causing the adjacency to bounce. However, I was doing this in IOS XR >> and it clearly bounced OSPF when I changed the MTU. I asked around on the >> cisco-nsp list, but so far no one knows why OSPF would bounce like that in >> IOS XR. One person thought that perhaps since it is a hardware forwarding >> platform, interface buffer memory had to be reallocated after the MTU >> change, but that was just a guess. If anyone knows, feel free to end the >> mystery. lol I know it won't bounce the adjacency in IOS, at least on the >> hardware and images I tested it on. And that makes sense to me. The MTU is >> not in the hello packets in OSPF; it's in the DBD packets. >> >> John >> >> >> On Fri, Jan 4, 2013 at 7:14 PM, Paul Negron <negron.paul_at_gmail.com> wrote: >>> >>> I do like that feature. >>> >>> I also love the way ISIS handles MTU mismatch which is another big >>> problem we >>> have in real networks. >>> You do not just simply ignore it as you do with OSPF. >>> >>> Paul >>> Paul Negron >>> CCIE# 14856 >>> negron.paul_at_gmail.com >>> >>> >>> On Jan 4, 2013, at 1:17 PM, Yuri Bank <yuribank_at_gmail.com> wrote: >>> >>> > Except that with the IS-IS the hostname is carried in each routers LSP >>> > (hostname TLV), so there is no dependency on DNS, or manual >>> > configuration >>> > on the routers required (Which is very nice imho). >>> > >>> > -Yuri >>> > >>> > >>> > On Fri, Jan 4, 2013 at 12:10 PM, Marko Milivojevic >>> <markom_at_ipexpert.com>wrote: >>> > >>> >> You mean the output you'd get if you used "ip ospf name-lookup" ;-) >>> >> >>> >> -- >>> >> Marko Milivojevic - CCIE #18427 (SP R&S) >>> >> Senior CCIE Instructor - IPexpert >>> >> >>> >> On Fri, Jan 4, 2013 at 12:07 PM, rakesh madupu <raaki.88_at_gmail.com> >>> >> wrote: >>> >>> For me, I love isis in our customer deployments because it shows >>> >>> neighboring devices names which is peers with, specially with RR's >>> >>> names >>> >> , >>> >>> life get so much simpler instead of reading an Ip address and >>> >> associating it >>> >>> again :) >>> >>> >>> >>> >>> >>> On Sat, Jan 5, 2013 at 12:34 AM, Marko Milivojevic >>> >>> <markom_at_ipexpert.com> >>> >>> wrote: >>> >>>> >>> >>>> IS-IS supports multiple routed protocols, i.e. IPv4 and IPv6, >>> >>>> whereas >>> >>>> OSPF doesn't. >>> >>>> >>> >>>> Also, in the time when MPLS-TE was emerging as a technology, IS-IS >>> >>>> behavior to flood unknown TLVs instead of resetting adjacencies when >>> >>>> it receives them (OSPF does that when it receives an unknown LSA). >>> >>>> meant a very controlled deployment of new technologies. The fact >>> >>>> it's >>> >>>> not IP, also has some security benefits (cannot be remotely >>> >>>> attacked). >>> >>>> Etc. >>> >>>> >>> >>>> What Joseph said is... not quite the reason, since IS-IS also has a >>> >>>> requirement for a contiguous L2 area. >>> >>>> >>> >>>> -- >>> >>>> Marko Milivojevic - CCIE #18427 (SP R&S) >>> >>>> Senior CCIE Instructor - IPexpert >>> >>>> >>> >>>> On Fri, Jan 4, 2013 at 10:34 AM, Imran Ali <immrccie_at_gmail.com> >>> >>>> wrote: >>> >>>>> marko i need to know why they use is-is over ospf >>> >>>>> >>> >>>>> On Fri, Jan 4, 2013 at 8:53 PM, Marko Milivojevic < >>> >> markom_at_ipexpert.com> >>> >>>>> wrote: >>> >>>>>> >>> >>>>>> In reality, for this purpose, IS-IS and OSPF are pretty much the >>> >>>>>> same >>> >>>>>> (Type 2 vs Pseudonode LSP). They both use a very similar approach >>> >>>>>> to >>> >>>>>> solve the same calculation problem. >>> >>>>>> >>> >>>>>> Carriers tend to use IS-IS for one other reason (to some extent >>> >>>>>> remedied by OSPFv3). This is a separate discussion though. >>> >>>>>> >>> >>>>>> -- >>> >>>>>> Marko Milivojevic - CCIE #18427 (SP R&S) >>> >>>>>> Senior CCIE Instructor - IPexpert >>> >>>>>> >>> >>>>>> >>> >>>>>> Blogs and organic groups at http://www.ccie.net >>> >>>>>> >>> >>>>>> >>> >> >>> >> _______________________________________________________________________ >>> >>>>>> Subscription information may be found at: >>> >>>>>> http://www.groupstudy.com/list/CCIELab.html >>> >>>> >>> >>>> >>> >>>> Blogs and organic groups at http://www.ccie.net >>> >>>> >>> >>>> >>> >>>> _______________________________________________________________________ >>> >>>> Subscription information may be found at: >>> >>>> http://www.groupstudy.com/list/CCIELab.html >>> >>>> >>> >>>> >>> >>>> >>> >>>> >>> >>>> >>> >>>> >>> >>>> >>> >>> >>> >>> >>> >>> >>> >>> -- >>> >>> Any Fool can Know The Point is to Understand - Einstein >>> >>> >>> >>> www.cciematrix.com >>> >> >>> >> >>> >> Blogs and organic groups at http://www.ccie.net >>> >> >>> >> >>> >> _______________________________________________________________________ >>> >> Subscription information may be found at: >>> >> http://www.groupstudy.com/list/CCIELab.html >>> > >>> > >>> > Blogs and organic groups at http://www.ccie.net >>> > >>> > _______________________________________________________________________ >>> > Subscription information may be found at: >>> > http://www.groupstudy.com/list/CCIELab.html >>> >>> >>> Blogs and organic groups at http://www.ccie.net >>> >>> _______________________________________________________________________ >>> Subscription information may be found at: >>> http://www.groupstudy.com/list/CCIELab.html >>> >>> >>> >>> >>> >>> >>> >> > > > > -- > Any Fool can Know The Point is to Understand - Einstein > > www.cciematrix.com Blogs and organic groups at http://www.ccie.netReceived on Sat Jan 05 2013 - 13:05:49 ART
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