From: Peter van Oene (pvo@usermail.com)
Date: Mon Apr 12 2004 - 10:05:33 GMT-3
At 03:32 AM 4/12/2004, Richard Dumoulin wrote:
>Hi Peter, I am not sure I understand your question. I only know that the
>concept of forwarding address was reflected in the ios at some point.
Well, I was hoping we'd get the theoretical reason for this issue posted to
the list for those interested in understanding the technology, vs knowing
what commands to type to avoid a particular pitfall . I worked a pretty
good sizes EIGRP / OSPF migration that ran into a lot of forwarding address
inter area routing issues which are well rooted in theory, but arcane to
some degree.
>-----Original Message-----
>From: Peter van Oene [mailto:pvo@usermail.com]
>Sent: lunes, 12 de abril de 2004 4:54
>To: ccielab@groupstudy.com
>Subject: RE: advertise ospf as 192.168.1.1 /29 0.0.0.0 area 0 and
>
>
>At 01:51 PM 4/11/2004, Richard Dumoulin wrote:
> >Allan,
> >
> > I would use 0.0.0.0 to go faster on the exam but I would be careful
> >when configuring asbr's as mentioned by Serran on multiaccess
> >interfaces.
> >
> >I have just found a case where using the wild card mask instead of
> >0.0.0.0 was not appropriate. Redistribution was being done on the asbr
> >but the only way to have full connectivity was to have the asbr
> >advertise his own address (forwarding address) for the redistibuted
> >routes,
>
>Do you know why this is? Ie, what is the issue at play here?
>
>
>
>
> >Regards
> >
> >--Richard
> >
> >
> >-----Original Message-----
> >From: Scott Morris [mailto:swm@emanon.com]
> >Sent: domingo, 11 de abril de 2004 15:30
> >To: 'Allan Wells'; ccielab@groupstudy.com
> >Subject: RE: advertise ospf as 192.168.1.1 /29 0.0.0.0 area 0 and not
> >0.0.0.7
> >
> >
> >You need to understand the behavior of the "network" command with IGP
> >protocols (BGP is different, in a lot of things!).
> >
> >The network command does not specifically say which networks to
> >advertise. Instead, it indicates to the router which networks will
> >participate in the routing protocol. If the IP address of an interface
> >falls within that range, then it is 'tagged' as participating in the
> >routing protocol. THEN the actual network that the interface has will
> >be brought in.
> >
> >For example, if you have:
> >
> >E0/0 = 10.0.0.1/24
> >S0/0 = 10.0.1.1/24
> >S0/1 = 10.0.2.1/24
> >E1/0 = 10.0.3.1/24
> >
> >You can say:
> >
> >Network 10.0.0.1 0.0.0.0 area 0 and this will only match the e0/0
> >Network 10.0.0.0 0.0.0.255 area 0 and only e0/0 will fall within that
> >range Network 10.0.0.0 0.0.0.3 area 0 and still only e0/0 will fall
> >within that range Network 10.0.0.0 0.0.1.255 area 0 and both e0/0 and
> >s0/0 will fall in here Network 10.0.0.0 0.0.3.255 area 0 and all four
> >interfaces will participate in ospf Network 0.0.0.0 255.255.255.255
> >area 0 and every single interface on the router will participate in
> >ospf
> >
> >There are many ways to do it, but the only thing you are indicating to
> >the router is which interfaces participate in the routing protocol.
> >The networks advertised comes as a later step within ospf.
> >
> >HTH,
> >
> >
> >Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> >CISSP, JNCIS, et al. IPExpert CCIE Program Manager IPExpert Sr.
> >Technical Instructor swm@emanon.com/smorris@ipexpert.net
> >http://www.ipexpert.net
> >
> >
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> >Allan Wells
> >Sent: Sunday, April 11, 2004 5:34 AM
> >To: ccielab@groupstudy.com
> >Subject: advertise ospf as 192.168.1.1 /29 0.0.0.0 area 0 and not
> >0.0.0.7
> >
> >Hi,
> >
> >
> >
> >I have been doing some labs and looking at all the solutions.
> >
> >
> >
> >Why is it some labs setup OSPF to use wildcard mask 0.0.0.0 with say
> >/29 multipoint hub and spoke network
> >
> >As apposed to to using 0.0.0.7 mask also I tried this config with eigrp
> >and theirs no problem their either what is the better way and why.
> >
> >
> >
> >I always was under the impression we need to advertise the mask of the
> >network in the above example 0.0.0.7 obviously not.
> >
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