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auto-summary and  ip summary-address rip comparison

Posted on 2006-06-19
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Last Modified: 2009-01-22
Case1
When auto-summary is enabled the output was

Router2#show 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
 
       2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C         2.2.2.16/28 is directly connected, Loopback2
C         2.2.2.32/27 is directly connected, Loopback22
R      163.1.0.0/16 [120/1] via 192.168.1.1, 00:00:15, Serial0/1
C      192.168.1.0/24 is directly connected, Serial0/1[/code]

When auto-summary is disabled the output:

Router2#show 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
 
       2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C         2.2.2.16/28 is directly connected, Loopback2
C         2.2.2.32/27 is directly connected, Loopback22
       163.1.0.0/16 is variably subnetted, 3 subnets, 3 masks
R         163.1.192.0/18 [120/1] via 192.168.1.1, 00:00:18, Serial0/1
R         163.1.0.0/16 [120/1] via 192.168.1.1, 00:00:47, Serial0/1
R         163.1.8.0/21 [120/1] via 192.168.1.1, 00:00:18, Serial0/1
C      192.168.1.0/24 is directly connected, Serial0/1[/code]



Case 2 :
When auto-summary is disabled the output:

Router2#show 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
 
       2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C         2.2.2.16/28 is directly connected, Loopback2
C         2.2.2.32/27 is directly connected, Loopback22
       163.1.0.0/16 is variably subnetted, 3 subnets, 3 masks
R         163.1.192.0/18 [120/1] via 192.168.1.1, 00:00:18, Serial0/1
R         163.1.0.0/16 [120/1] via 192.168.1.1, 00:00:47, Serial0/1
R         163.1.8.0/21 [120/1] via 192.168.1.1, 00:00:18, Serial0/1
C      192.168.1.0/24 is directly connected, Serial0/1[/code]

When I enabled ip summary-address rip 163.1.0.0 255.255.0.0 on S0/1 Router1 , then I checked the below command


Router2#show 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
 
       2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C         2.2.2.16/28 is directly connected, Loopback2
C         2.2.2.32/27 is directly connected, Loopback22
R      163.1.0.0/16 [120/1] via 192.168.1.1, 00:00:11, Serial0/1
C      192.168.1.0/24 is directly connected, Serial0/1[/code]

What is the difference between the "no auto-summary" and  "ip summary-address rip" ?
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Question by:zillah
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by:Scotty_cisco
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What version of RIP are you using... version 1 is classfull and will not allow for any kind of subneting.  Try using rip version 2 it will allow for the interdomain routing.

Thanks
Scott

To answer your question though the main difference between auto summary and no auto summary is that the router records all networks and routes with auto summary it summarizes the routes...  For instance

lets say you have 10 networks all starting 10.1.1.0, 10.2.1.0, 10.3.1.0 ect

with auto summary your route will show 10.0.0.0 255.0.0.0 with no auto summary you will show all 10 routes.... this is just an example not a very clear one I am sure....

Thanks
scott
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by:zillah
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Thanks scott for your help.

((Try using rip version 2 it will allow for the interdomain routing.))
It is already version 2.

((difference between auto summary and no auto summary ))
My query is What is the difference between the "no auto-summary" and  "ip summary-address rip" ?
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by:Scotty_cisco
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ip summary-address rip
To configure a Cisco router running RIPv2 to advertise a summarized local IP address pool on a network access server so that the address pool can be provided to dialup clients and specify the IP address and network mask that identify the routes to be summarized, use the ip summary-address rip router configuration command.

auto-summary (RIP)
To restore the default behavior of automatic summarization of subnet routes into network-level routes, use the auto-summary command in router configuration mode. To disable this function and send subprefix routing information across classful network boundaries, use the no form of this command.

auto-summary

no auto-summary

Usage Guidelines
Route summarization reduces the amount of routing information in the routing tables.

RIP Version 1 always uses automatic summarization. If you are using RIP Version 2, you can turn off automatic summarization by specifying the no auto-summary command. Disable automatic summarization if you must perform routing between disconnected subnets. When automatic summarization is off, subnets are advertised.


thanks
Scott

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by:zillah
Comment Utility
((My query is What is the difference between the "no auto-summary" and  "ip summary-address rip" ?))
Sorry, I meant to say: What is the difference between the "auto-summary" and  "ip summary-address rip"  ?

I have got an answer from this :
http://www.cisco.com/en/US/products/ps6350/products_command_reference_chapter09186a008046702d.html
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