From: swm@emanon.com
Date: Sat Jan 31 2009 - 18:03:51 ARST
heheheh... Yup, forgot about that one. 'No sync' is the default command
now, but you're right, if you need to turn it on, the BGP RFC states that the
router-id's must match.
Thanks for reminding me! :)
Scott
---- Message from Narbik Kocharians <narbikk@gmail.com> at 2009-01-31 10:26:01
------
>
>I totally agree with Scott, the OSPF router id is a 32 bit dotted decimal
number, it can be an IPv4 address, but it can also be any dotted decimal
number like "0.0.0.1" for R1 and so forth.
>
>One problem that you may run in to (In a CCIE LAB) is when you have OSPF and
BGP with synchronization enabled in an AS, the router that redistributes the
BGP routes into OSPF must have the same router-id configured on both routing
protocols (meaning OSPF and BGP router-id must be identical on that router)
and in this case you won't be able to use anything other than a valid IP
address, because BGP's router-id must be a valid IP address.
>
>Hope this helped.
>
>
>On Sat, Jan 31, 2009 at 3:57 AM, ciscozest <mailto:ciscozest@gmail.com >
wrote:
>
>
>Dear Scott, Jared, Roy and Jason,
>
>Thank you all for the input. Really appreciate that. Have a nice weekend :)
>
>
>-----Original Message-----
>From: mailto:swm@emanon.com [mailto:mailto:swm@emanon.com ]
>Sent: Saturday, 31 January 2009 3:23 PM
>To: Jared Scrivener; 'Jason Madsen'; 'ciscozest'
>Cc: 'Cisco certification'; 'Cisco certification'
>
>
>
>Subject: RE: about OSPF router ID
>
>Actually, it not only doesn't need to be pingable, but it doesn't even need
to be a valid IPv4 address. It's simply a 32-bit number.
>
>If you're bored, make your router-id's 240.1.1.1, 240.1.1.2, 240.1.1.3, etc.
Definitely can't put that on an IP interface... Definitely can't ping it.
But it works just fine.
>
>Jared's got a point about name lookups, but on the other hand, if you
properly populate your DNS lookups you'll be good on that one!
>
>Real life, most people use a loopback, whatever your main management
interface happens to be. Just keeps things simple. But it's just a 32-bit
number, so the fact that it relates to an actual IP address is for OUR
benefit, not the routers'!
>
>Scott
>
>
>---- Message from "Jared Scrivener" <mailto:jscrivener@ipexpert.com > at
2009-01-30 21:25:18 ------
>>Whilst it is true that an OSPF Router ID doesn't have to be pingable, it
>>generally makes life easier to use a reachable IP (normally Loopback 0).
>>
>>Let's say that you are asked to also turn on "ip ospf domain-lookup" which
>>will translate your neighbor's Router-ID into a DNS name (which will either
>>be defined by a hosts file or received via DNS).
>>
>>If you do it via hosts entries and your are ALSO a DNS server then your DNS
>>clients would receive an unreachable IP address when they ping via DNS
name.
>>
>>I know that's a rare case, but given the nature of question interdependency
>>on the lab (and the evil nature of workbook vendors) I personally use L0 as
>>my OSPF Router-ID (and set it manually using the "router-id" command) every
>>time unless otherwise directed.
>>
>>Cheers,
>>
>>Jared Scrivener CCIE3 #16983 (R&S, Security, SP), CISSP
>>Technical Instructor - IPexpert, Inc.
>>Telephone: +1.810.326.1444
>>Fax: +1.810.454.0130
>>Mailto: mailto:jscrivener@ipexpert.com
>>
>>-----Original Message-----
>>From: mailto:nobody@groupstudy.com [mailto:mailto:nobody@groupstudy.com ]
On Behalf Of
>>Jason Madsen
>>Sent: Friday, 30 January 2009 9:01 PM
>>To: ciscozest
>>Cc: Cisco certification; Cisco certification
>>Subject: Re: about OSPF router ID
>>
>>OSPF Router IDs can be any UNIQUE IPv4 address...they don't have to be
>>addresses assigned to an interface.
>>
>>On Fri, Jan 30, 2009 at 6:56 PM, ciscozest <mailto:ciscozest@gmail.com >
wrote:
>>
>>> Hi all,
>>>
>>>
>>>
>>> I read Cisco press book stated that OSPF router ID do not need to be
>>> pingable. In this case if I use a router ID which is not assigned to any
>>> interface on that router, would this cause any issue such as OSPF
>>> adjacency,
>>> LSA table advertisement, etc? Has anyone do this before and can enlighten
>>> me? Thanks.
>>>
>>>
>>> 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/
>>
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>>
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>>
>>
>>
>
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>--
>Narbik Kocharians
>CCSI#30832, CCIE# 12410 (R&S, SP, Security)
>http://www.MicronicsTraining.com www.MicronicsTraining.com
>http://www.Net-Workbooks.com www.Net-Workbooks.com
>Sr. Technical Instructor
Blogs and organic groups at http://www.ccie.net
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