From: Salah ElShekeil (salah.elshekeil@gmail.com)
Date: Wed Mar 25 2009 - 05:06:23 ART
Its used to prevent the router from forwarding traffic for destinations
inside the summary that it doesn't have longer match for,
Sometimes it's undesirable, it the router itself just have a default route
to the destination and it generating a summary,
the traffic will be dropped by the router because it does not have a longer
match for it, even if there is a default route
More over you will see the AD if the summary is 5, you can give static route
which is by default AD 1, pointing to the default route of the router it
self,
it will prevent the NULL, or you can do
ip summ ei 100 0.0.0.0 0.0.0.0 255
this also will prevent null
HTH
ex.
R4 lo 1 ip add 1.1.4.1/24
R5 lo 1 ip add 1.1.5.1/24
R1 fa 0/1
ip add 192.168.1.1 255.255.255.0
ip sum ei 100 0.0.0.0 0.0.0.0
R4------------R5---------------R6
show ip route in R5
0.0.0.0/0 via 192.168.1.1
in R5 interface connected to R6
ip summ ei 100 1.1.4.0 255.255.254.0
try to ping from R6 to 1.1.4.1
you will not be able, but u can ping R5 loopback, because R5 have a longer
match for its loopback
show ip route 1.1.5.1 in R5 its directly connected
show ip route 1.1.4.0 in R5
there is no entry !!!!
the traffic will be discarded by R5, because it doesnt have a longer match
for 1.1.4.1
to solve that
give in R5
ip route 1.1.4.1 255.255.255.255 192.168.1.1
try again to ping from R6 will be able coz R5 have longer match for R4
loopback
you can also do another thing
Instead of putting
Ip sum ei 100 1.1.4.0 255.255.254.0
Do
Ip sum ei 100 1.1.4.0 255.255.254.0 255
With AD of 255
HTH
Salah
On Wed, Mar 25, 2009 at 10:07 AM, marish shah <contactmarish@gmail.com>wrote:
> Thanks all for ur reply ,But here is one more Q
>
> Why eigrp generate null0 route with summary routes.
>
>
> Thanks.
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