From: swm@emanon.com
Date: Sat Jan 31 2009 - 23:56:19 ARST
The router-id in both is simply a 32-bit number.
Your call.
Scott
---- Message from "ciscozest" <ciscozest@gmail.com> at 2009-02-01 08:11:46
------
>
>
>So in case of OSPF and BGP exist on the same router, does the router ID must
be pingable or just a valid IPv4 address?
>Thanks.
>
>
>
>From: Narbik Kocharians [mailto:narbikk@gmail.com]
>Sent: Sunday, 1 February 2009 4:26 AM
>To: ciscozest
>Cc: swm@emanon.com; Jared Scrivener; Jason Madsen; Cisco certification; Cisco
certification
>Subject: Re: about OSPF router ID
>
>
>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/"
>target="_blank
>>>
>>> _______________________________________________________________________
>>> 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
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