From: Magondo, Michael (Michael.Magondo@dcs.gov.za)
Date: Fri Dec 20 2002 - 05:29:51 GMT-3
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
C 1.1.1.1 is directly connected, Loopback0
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
D 172.16.5.0/24 is a summary, 03:55:51, Null0
C 172.16.5.0/25 is directly connected, Loopback1
D 172.16.6.0/24 [90/20640000] via 192.168.1.2, 03:53:17,
Serial0/0.1
D 172.16.2.0/24 [90/2195456] via 192.168.2.2, 03:54:30,
Serial0/0.2
D 172.16.3.0/24 [90/20640000] via 192.168.1.3, 03:56:00,
Serial0/0.1
192.168.1.0/29 is subnetted, 1 subnets
C 192.168.1.0 is directly connected, Serial0/0.1
C 192.168.2.0/24 is directly connected, Serial0/0.2
R1#
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
172.16.0.0/24 is subnetted, 4 subnets
D 172.16.5.0 [90/2297856] via 192.168.2.1, 03:56:59, Serial0
D 172.16.6.0 [90/21152000] via 192.168.2.1, 03:55:45, Serial0
C 172.16.2.0 is directly connected, Ethernet0
D 172.16.3.0 [90/21152000] via 192.168.2.1, 03:56:59, Serial0
192.168.1.0/29 is subnetted, 1 subnets
D 192.168.1.0 [90/21024000] via 192.168.2.1, 03:56:59, Serial0
C 192.168.2.0/24 is directly connected, Serial0
R4#
Thanks in advance,
Hunt
.
.
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