From: Magondo, Michael (Michael.Magondo@dcs.gov.za)
Date: Fri Dec 20 2002 - 10:13:32 GMT-3
Hunt
Last thing.
From the advertising behaviour of RIP, if a subnet to be advertised in
the same major net as the interface that the update is to be sourced on
and the subnet mask of the subnet is different from the subnet mask of
the interface, then the subnet is dropped from the advert.
This is why you will find the 172.16.5.0 /25 subnet is dropped from the
advert to R5 from R4.
That's my 2c
Cheers
Mike
-----Original Message-----
From: Magondo, Michael
Sent: 20 December 2002 02:55 PM
To: 'Hunt Lee'
Cc: 'ccielab@groupstudy.com''
Subject: RE: What if EIGRP routes have different masks than RIP?
Hunt
We can establish from this that even after removal of summary-address on
R1 the 172.16.5.0 subnet is received and advertised as a /25 by R4. What
I am not sure of is whether this route is dropped by R4 on
redistribution or by R5 on receiving the advertised route.
Do you think you could do a debug ip rip? I would like to see how many
routes R4 advertises to R5. If only 4 routes are advertised then what it
means is on redistribution R4 discards 172.16.5.0/25 route.
Regards
Michael
-----Original Message-----
From: Hunt Lee [mailto:ciscoforme3@yahoo.com.au]
Sent: 20 December 2002 01:04 PM
To: Magondo, Michael
Subject: RE: What if EIGRP routes have different masks than RIP?
Hi Mike,
When I remove the summary-address on R1, the route to 172.16.5.0
disappears from R5,
but it is still there at R4.
R4#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks
D 172.16.5.0/25 [90/2297856] via 192.168.2.1, 00:03:03, Serial0
D 172.16.6.0/24 [90/21152000] via 192.168.2.1, 00:03:03, Serial0
C 172.16.2.0/24 is directly connected, Ethernet0
D 172.16.3.0/24 [90/21152000] via 192.168.2.1, 00:03:03, Serial0
192.168.1.0/29 is subnetted, 1 subnets
D 192.168.1.0 [90/21024000] via 192.168.2.1, 00:03:03, Serial0
C 192.168.2.0/24 is directly connected, Serial0
R4#
R5# sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 3 subnets
R 172.16.6.0 [120/5] via 172.16.2.1, 00:00:17, Ethernet0
C 172.16.2.0 is directly connected, Ethernet0
R 172.16.3.0 [120/5] via 172.16.2.1, 00:00:17, Ethernet0
10.0.0.0/24 is subnetted, 1 subnets
C 10.0.0.0 is directly connected, Dialer0
R 192.168.1.0/24 [120/5] via 172.16.2.1, 00:00:17, Ethernet0
R 192.168.2.0/24 [120/5] via 172.16.2.1, 00:00:17, Ethernet0
30.0.0.0/24 is subnetted, 1 subnets
C 30.3.3.0 is directly connected, Loopback0
R5#
Hunt
--- "Magondo, Michael" <Michael.Magondo@dcs.gov.za> wrote: > Hunt
>
> This is my impression from your setup.
>
> On R1 you summarize the 172.16.5.0 /25 to a /24 network. This along
with
> all other 172.16 subnets is advertised to R4 via EIGRP. From this R4
> places these subnets in its routing table. The no auto-summary on R1
> prevents summarization of 172.16 subnets on the major net boundary
> (/16). The 192.168.1.0 /29 subnet is also advertised without
> summarization due to this command as well.
>
> On R4 the 192.168.1.0 / 29 subnet is summarized according to the major
> net boundary on redistribution to RIP due to the change of the major
net
> and the lack of subnet masks with RIPv1 as discussed before. The
172.16
> subnets are redist into RIP as is due to the fact that the router
> currently has an interface in the same major network and thus the /24
> mask is used. This results in advertising of all the 172.16 subnets to
> R5.
>
> I just need to confirm that when you remove the summary-address on R1,
> what routes are included R4. This should explain why it is removed
from
> R5
>
> Hope that help.
>
> Mike
>
> P.s. I speak under correction here as I cannot lab this.
>
>
> -----Original Message-----
> From: Hunt Lee [mailto:huntl@webcentral.com.au]
> Sent: 20 December 2002 09:20 AM
> To: Magondo, Michael
> Subject: RE: What if EIGRP routes have different masks than RIP?
>
> Hi Mike,
>
> Thanks for that. Then why didn't it happen for the other EIGRP route
> (172.16.5.0 /25) as well?? i.e. As soon as I take the
"summary-address"
> off
> on R1, R5 immediately lost its routes to 172.16.5.0 /25 subent.
>
> Hunt
>
>
> -----Original Message-----
> From: Magondo, Michael [mailto:Michael.Magondo@dcs.gov.za]
> Sent: Friday, 20 December 2002 5:15 PM
> To: Hunt Lee; ccielab@groupstudy.com
> Subject: RE: What if EIGRP routes have different masks than RIP?
>
>
> Hunt
>
> From what I see, on R4 you have redistributed the EIGRP routes into
RIP.
> Your /29 route for the 192.168.1.0 subnet will lose its subnet mask as
> you are using RIPv1, thus the route will be defined by the major
network
> boundary i.e. /24, thus when these routes are advertised to R5, the
> route is advertised as a /24 route.
>
> From my understanding this is the expected behavior of RIPv1.
>
> Hope that helps
>
> Mike
>
>
> -----Original Message-----
> From: Hunt Lee [mailto:huntl@webcentral.com.au]
> Sent: 20 December 2002 05:40 AM
> To: 'ccielab@groupstudy.com'
> Subject: What if EIGRP routes have different masks than RIP?
>
> Guys,
>
> I'm sure this question has been asked many times before, but can
someone
> kindly explain to me again? There are some /25 routes & /29 routes in
> EIGRP
> that I need to redistribute into RIP v1. The serial frame relay link
> that
> connects R1 with R4 has a /24 mask, and so as the Ethernet link that
> connects R4 & R5. How can I inject /25 & /29 EIGRP routes into a
> classful
> routing domain in a case such as this?
>
>
> 172.16.5.1 /25
> ---------------
> |
> R1
> / | \
> / | \
> R2 R3 R4 --- R5
>
> The entire Hub & Spoke network is EIGRP only, except R4 which is
running
> both EIGRP & RIPv1 (& mutual redistribution between the 2 protocols),
&
> R5
> is running RIPv1 only.
>
> R1's Multipoint interface to R2 & 3 - 192.168.1.1 /29
> R1's P-2-P interface to R4 - 192.168.2.1 /24
> R2's FR interface - 192.168.1.2 /29
> R3's FR interface - 192.168.1.3 /29
> R4's FR interface to R1 - 192.168.2.2 /24
> R4's Ethernet to R5 - 172.16.2.1 /24
> R5's interface - 172.16.2.2 /24
>
> From what I read from Cisco books, since the RIPv1 network in this
e.g.
> is
> /24, both routes 192.168.1.0/29 & 172.16.5.0/25 would need to be
> summarized
> into a /24 (at R1) before R4 would be willing to pass these routes to
> R5.
>
> However, on the moment, all I had at R1 is:-
>
> interface Serial0/0.2 point-to-point
>
> ip address 192.168.2.1 255.255.255.0
>
> ip summary-address eigrp 65001 172.16.5.0 255.255.255.0 5
>
> frame-relay interface-dlci 130
>
> And you can see that R5 "somehow" managed to get the Frame-Relay route
> (192.168.1.0/29) - into a /24, don't undersantd how.
>
> R5#sh ip route
> Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B -
BGP
>
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
>
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
>
> E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
>
> i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
> inter
> area
> * - candidate default, U - per-user static route, o - ODR
>
> P - periodic downloaded static route
>
>
>
> Gateway of last resort is not set
>
>
>
> 172.16.0.0/24 is subnetted, 4 subnets
>
> R 172.16.5.0 [120/5] via 172.16.2.1, 00:00:24, Ethernet0
>
> R 172.16.6.0 [120/5] via 172.16.2.1, 00:00:24, Ethernet0
>
> C 172.16.2.0 is directly connected, Ethernet0
>
> R 172.16.3.0 [120/5] via 172.16.2.1, 00:00:24, Ethernet0
>
> 10.0.0.0/24 is subnetted, 1 subnets
>
> C 10.0.0.0 is directly connected, Dialer0
>
> R 192.168.1.0/24 [120/5] via 172.16.2.1, 00:00:24, Ethernet0
>
> R 192.168.2.0/24 [120/5] via 172.16.2.1, 00:00:24, Ethernet0
>
> 30.0.0.0/24 is subnetted, 1 subnets
>
> C 30.3.3.0 is directly connected, Loopback0
>
> R5#
>
> Yet I can see it clearly that the Frame Relay routes were definitely a
> /29
>
> R1#sh ip route
>
> Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B -
BGP
>
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
>
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
>
> E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
>
> i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
> inter
> area
> * - candidate default, U - per-user static route, o - ODR
>
> P - periodic downloaded static route
>
>
>
> Gateway of last resort is not set
>
>
>
> 1.0.0.0/32 is subnetted, 1 subnets
>
=== message truncated ===
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