Subject: Re: Changing router name...

From: "[email-masked]" <[email-masked]>
Date: Mon, 14 Apr 2003 18:42:53 +0200

Hi Alok, hi all,

>it would be router-id
yes i intended router-id: router-id is the number of the 
highest interface on a router, isn' t it?

>in general you would make loopback as router-id (i think)
NO

>>i'd like to make you a question: 
>>what problems could be in a network in which there is 
>>a router changing its name? I am thinking to a MPLS-TE 
>>scenario in which there are RSVP and OSPF and in which i 
>>use Explicit Route Objects for Traffic Engineering. 

>>Since in OSPF the name of each router is the address of the highest
>>interface, is it possible that this particular interface goes down? 
>>In a router (for example CISCO, JUNIPER, ecc...) could it happen?

>>If that particular interface (for example x.y.33.1 ) goes down and/or 
>>the operating system of the router eliminates it, after some hellos, 
>>we have the generation of LSA Update, so all network will know there 
>>is a NEW router in the net (for example x.y.22.1)! What can it happen 
>>to the LSPs crossing that router and not interested by the interface's failure? 

>>Infact, we have one ERO (explicit route object) for each LSP crossing 
>>the router; in each ERO of the LSPs not interested by the failure, 
>>we have x.y.33.1; after four hellos, the router x.y.33.1 will not exist
>>more in the net! In the same way if i establish new LSPs, 
>>they will have the ERO containing x.y.22.1, so if the interface becomes
>>active after a certain period, the router will return to the name x.y.33.1 
>>and we' l have the same problem.

Thanks in advance for your kind answers and observations.
Giovanni

Coritel - Rome

---

From: alok <[email-masked]>
Date: Mon, 14 Apr 2003 22:49:25 +0530

----- Original Message -----
From: [email-masked] <[email-masked]>
To: <[email-masked]>
Sent: Monday, April 14, 2003 10:12 PM
Subject: Re: Changing router name...

> >in general you would make loopback as router-id (i think)

why not?

---

From: Erblichs <[email-masked]>
Date: Mon, 14 Apr 2003 10:53:30 -0700

Group,

        If you would be running two or more OSPF
        processes within your router, do you
        still want them both to use the highest
        interface or both use the loopback interface
        as the router-id?

        Mitchell Erblich
        Sr . Software Engineer
        ----------------------------

---

From: Scott Whyte <[email-masked]>
Date: Mon, 14 Apr 2003 11:23:54 -0700

>         interface or both use the loopback interface

I would prefer a loopback per process.

-Scott

---

From: Alok Dube <[email-masked]>
Date: Tue, 15 Apr 2003 00:43:20 +0530

multiple loopbacks...at least 1 per vrf.

"preferably" (thats my preference as i anyways get a /32 for router-id,
why introduce a lo0/32 too to make it reachable via tha OSPF process?)
each loopback being the "router-id" for that ospf-process? (presuming ospf
process are dosjoint sets / 2 seperate OSPF instances not releated to one
another)....

---

From: Scott Whyte <[email-masked]>
Date: Mon, 14 Apr 2003 11:53:58 -0700

> multiple loopbacks...at least 1 per vrf.

Why?  Do you put multiple VRFs into a single OSPF process?

-Scott

---

From: Alok Dube <[email-masked]>
Date: Tue, 15 Apr 2003 01:04:44 +0530

> Why?  Do you put multiple VRFs into a single OSPF process?

Hi,

no i dont, i could have a loopback interface per process...

think i missed your point....

i meant 1 loopback per vrf atleast... (that actually came to me from BGP
presuming i was running BGP with the CE and it wasnt 1 hop away)..but yes,
same applies for OSPF, the interface is never down and you could have
multiple unnumbered P2Ps on it...

---

From: Scott Whyte <[email-masked]>
Date: Mon, 14 Apr 2003 13:42:32 -0700

> no i dont, i could have a loopback interface per process...

Then VRFs are irrelvant to Mitchell's original question, since you have
one OSPF process per VRF what you are really saying is at least 1
loopback/OSPF process.

> multiple unnumbered P2Ps on it...

BGP is also irrelvant to this question.

-Scott

---

From: Erblichs <[email-masked]>
Date: Mon, 14 Apr 2003 16:11:30 -0700

Alok,

        Simplying, multiple OSPF process support has
        additional requirements.

        One CAN NOT just takes the highest value
        interface or select a loopback.

        If there are multiple interfaces or
        loopbacks, then one must be able to identify
        that the object in question has been allocated
        to a particular process and thus is not eligible
        to be allocated a 2nd time..

        Mitchell Erblich
        Sr Software Engineer
        ----------------------------------

---

From: Yasuhiro Ohara <[email-masked]>
Date: Tue, 15 Apr 2003 10:07:08 +0900

Hi, Erblichs

>         interface or select a loopback.

I don't think so. To be more precise, taking the highest value as RID
for a particular OSPF process will be above "the interfaces enabled
for that OSPF process". Generally it is likely that the operational
interfaces differs per OSPF processes (and it may not be even overlapped).

Changing which interface to enable per OSPF processes is the easiest way
to controlling RID for the process, on the simplest algorithm to choose
RID (i.e. choosing highest value). Configuring multiple loopback interface
implies this I guess.

>         to be allocated a 2nd time..

Besides all, using the same RID for multiple OSPF process will
have no problem. What RID require is just to be unique within
a OSPF domain. If OSPF domain differs, duplication of RID
does not break anything.

regards,
yasu

---

From: Erblichs <[email-masked]>
Date: Wed, 16 Apr 2003 11:14:50 -0700

> RID (i.e. choosing highest value). Configuring multiple loopback interface

        If the interfaces of your router are separated by different domains,
        THEN your argument holds true.

        What I was going for was..

        Within a multiple OSPF process environment, as RIDs are selected,
        their should be some algorithm that verifies that each of them are
        unique.

        Since, the selection of a BMA environment uses RIDs as the 2nd
        component in DR/BDR elections (the first being priority), selecting
        the highest available interface value for your process RID,
        is not necessary the best option.
> a OSPF domain. If OSPF domain differs, duplication of RID

        To assume no interaction of OSPF proceess's is risky
        at best. At worst, you are dealing with duplicate RIDs.

        In my mind, not creating duplicate RIDs is just easier.