What if EIGRP routes have different masks than RIP?

From: Hunt Lee (huntl@webcentral.com.au)
Date: Fri Dec 20 2002 - 00:39:44 GMT-3


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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