From: Derek Small (Fuse) (dwsmall@xxxxxxxxxx)
Date: Fri Apr 21 2000 - 14:07:15 GMT-3
With OSPF you can summarize from a smaller subnets to larger ones, but you
can also "summarize" from larger subnets to smaller one as well. Try it.
We are adding a couple of new labs around the end of the month, and one of
them (502) will include this as part of the assignment. The summarize
option only checks to see if there is an active route that overlaps the
summary. The summary does not have to completely contain the entire active
route to be activated.
If the router has the following routing table
147.1.0.0 is subnetted
O 147.1.1.0/24 147.2.2.6
O 147.1.2.0/24 147.2.2.6
O 147.1.64.0/22 147.2.2.6
You can still issue the command:
router ospf 1
summ 147.1.64.0 255.255.255.0
You just have to be aware that you will only be advertising part of the
147.1.64.0/22 subnet into your FLSM area. If you want all four possible
segments or the actual subnet, you would need to add these summaries also.
summ 147.1.65.0 255.255.255.0
summ 147.1.66.0 255.255.255.0
summ 147.1.77.0 255.255.255.0
If you are only concerned about connectivity to the first part of the
subnet, however, you do not need them.
Thank You
Derek Small
dwsmall@fatkid.com
----- Original Message -----
From: Nnanna Obuba <obuba@bellatlantic.net>
To: Derek Small (Fuse) <dwsmall@fatkid.com>
Sent: Friday, April 21, 2000 11:21 AM
Subject: Re: Redisributing IGRP in OSPF (2)
> check out lab 8 from cciebootcamp..i think that's where all the fuss about
> not using summary addresses is coming from...the ospf addreses here cannot
> be summarized and redistributed into igrp cos ospf masks are /27 , while
the
> igrp addresses are mask /28. Of course if the masks were changed around,
the
> the summary address or are..range would work
>
> Nnanna
>
> ----- Original Message -----
> From: "Derek Small (Fuse)" <dwsmall@fatkid.com>
> To: "LASSERRE Grégory" <gregory.lasserre@arche.fr>; "ccielab groupstudy"
> <ccielab@groupstudy.com>
> Sent: Friday, April 21, 2000 9:47 AM
> Subject: Re: Redisributing IGRP in OSPF (2)
>
>
> This is a typical limitation of FLSM routing protocols. With a subnet of
> the 131.1.x.x network already attached to R22, you will not be able to
teach
> R22 about subnets with any masks besides the one R2 is already using. If
I
> assume your loopback addresses all have the form, x.x.x.1, then you can
just
> use area range statements on R1 to summarize these networks (actually you
> would be making the advertisements more granular not summarizing) with an
a
> mask of /26 instead of /18. If these were real interfaces that supported
> systems with addresses that covered the enter scope of the subnet you
would
> need to add subnets for each summary-subnet, ie.
>
> area 1 range 131.1.64.0 255.255.255.192
> area 1 range 131.1.64.64 255.255.255.192
> area 1 range 131.1.64.128 255.255.255.192
> area 1 range 131.1.64.192 255.255.255.192
> area 1 range 131.1.65.0 255.255.255.192
> area 1 range 131.1.65.64 255.255.255.192
> area 1 range 131.1.65.128 255.255.255.192
> area 1 range 131.1.65.192 255.255.255.192
> .......
> ......
> area 1 range 131.1.127.192 255.255.255.192
>
> Obviously this would be a pain in the rear, but would be your only option.
> Of course in the real world, you would convert the IGRP router to OSPF, or
> add a static route, or just have enough foresight to avoid the situation
> entirely through good addressing practices.
>
> Thank You
>
> Derek Small
> dwsmall@fatkid.com
>
>
> ----- Original Message -----
> From: LASSERRE Grégory <gregory.lasserre@arche.fr>
> To: ccielab groupstudy <ccielab@groupstudy.com>
> Sent: Friday, April 21, 2000 6:56 AM
> Subject: Redisributing IGRP in OSPF (2)
>
>
> >
> > Hi everybody,
> >
> > regarding IGRP-> OSPF redistribution problem i configured the following
> > network :
> >
> > R4500 --- Eth 131.1.1.192/26 --- R1 --- Serial 131.1.
> > 1.128/26 --- R10 --- Eth 131.1.10.128/26 --- R22
> >
> > R4500 has 3 loopbacks : on networks
> > - 131.1.64.0/18
> > - 131.1.128.0/18
> > - 131.1.192.0/18
> >
> > R4500 and R1 are in area 1
> > R1 and R10 in area 0
> > R1 is ABR
> > R10 ASBR and provide mutual redistribution between OSPF and IGRP
> > R22 routing protocol is only IGRP
> >
> > And here is the Problem : R22 is not able to reach the 3 loopback
networks
> > on R4500
> >
> > As you see, in this configuration, it's not possible to solve the
problem
> > by using :
> > 1/ Area range on R1
> > 2/ Secondary Address in /16 onR1, R10, and R22
> > 3/ Neither Loopback, static routes, or ip default-network on R22
> >
> > So as for me, it seems that the only solution available is to configure
a
> > static route
> > on R22 ("ip default network" or "ip route" commands)
> >
> > However i'm not really satisfied by this.
> > Does anyone see another solution to solve this ?
> >
> > (i was thinking policy-routing or tunnelling could help. I will make
some
> > tests this week end).
> >
> > Cheers
> > Greg.
> >
> > ------------------------------------------------------------------------
> > Gregory LASSERRE Tel. : +33 1 69 18 98 53
> > Network Engineer Fax : +33 1 69 28 55 01
> > ARCHE Groupe SIEMENS Std : +33 1 69 18 32 32
> > FRANCE
> >
> > E-mail : gregory.lasserre@arche.fr
> > ------------------------------------------------------------------------
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> > Gregory LASSERRE Tel. : +33 1 69 18 98 53
> > Network Engineer Fax : +33 1 69 28 55 01
> > ARCHE Groupe SIEMENS Std : +33 1 69 18 32 32
> > FRANCE
> >
> > E-mail : gregory.lasserre@arche.fr
> > ------------------------------------------------------------------------
> >
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 08:23:15 GMT-3