From: Waters, Kivas (UK72) (Kivas.Waters@xxxxxxxxxxxxx)
Date: Sat Dec 22 2001 - 09:16:27 GMT-3
Can anyone shed some light on the following issue?
IGRP---------------OSPF(area 0)----OSPF(area 1)
/24's /24's + /32's /24's + /32's
Reading all of the groupstudy emails concerning the mechanisms to enable an
IGRP domain to see all routes within an OSPF domain, it seems that there are
a number of ways to do this. Summarising the OSPF routes for example the
OSPF /32 loopbacks into say a /24 network can be achieved using the OSPF
"area range" or "summary address" commands. When it comes to loopbacks for
example, it appears that keeping all OSPF domain loopbacks out of area 0 and
then using the "area range " command is the most obvious and easiest method
of summarising the /32 networks into an IGRP comprehendable /24 network. On
the other hand, assuming that enough address space is available, creating
another loopback, redistributing connected and using the "summary address"
command will also work.
The question I have is this: if we are not permitted to manually configure
any static routes and we then decide to use the OSPF "area range" command,
then the Cisco IOS does not by default create a route to null0 to catch all
invalid packets destined for the summary address. Is it not MORE correct to
use the OSPF "summary address" command and have the IOS generate the route
to null0 thereby helping prevent routing loops and black holes.
What will the proctors accept? Any idea's?
regards
Ki
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