CCIE RS – Routing Concepts – Implement, Optimize and Troubleshoot Manual and Auto Summarization with any Routing Protocol

Implement, Optimize and Troubleshoot Manual and Auto Summarization with any Routing Protocol

Auto Summarization is when a a prefix is automatically summarized at a network boundary to it’s classful prefix. Example, a router changes the prefix 172.16.5.0/24 to 172.16.0.0/16.


RIP

By default RIP will automatically summarize subnet routes into network level routes

router rip
version 2
[no] auto-summary
network x.x.x.x

https://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfrip.html

Manual summarization can be done at an interface level. The summary entry will be entered into the RIP database

R1(config-if)#ip summary-address rip 1.1.1.1 255.255.255.0
R1(config-if)#
R1#sh int lo0
Loopback0 is up, line protocol is up 
 Hardware is Loopback
 Internet address is 1.1.1.1/32




R3#sh ip route
1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
R 1.1.1.0/24 [120/2] via 150.1.23.2, 00:00:05, GigabitEthernet0/1
R 1.1.1.1/32 [120/2] via 150.1.23.2, 00:00:12, GigabitEthernet0/1
 2.0.0.0/32 is subnetted, 1 subnets
R 2.2.2.2 [120/1] via 150.1.23.2, 00:00:12, GigabitEthernet0/1
 3.0.0.0/32 is subnetted, 1 subnets
C 3.3.3.3 is directly connected, Loopback0
 150.1.0.0/16 is variably subnetted, 3 subnets, 2 masks
R 150.1.12.0/24 [120/1] via 150.1.23.2, 00:00:12, GigabitEthernet0/1
C 150.1.23.0/24 is directly connected, GigabitEthernet0/1
L 150.1.23.3/32 is directly connected, GigabitEthernet0/1
R3#

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_rip/configuration/xe-3se/3850/irr-xe-3se-3850-book/irr-ipsum-adr-rip2.html


EIGRP

Auto summary is enabled in EIGRP by default.

Summary routers are given an administrative distance of 5

https://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfeigrp.html

Manual summarization can be performed at any point in the network

R1(config-if)#ip summary-address eigrp 1 0.0.0.0/0 



R3(config-router)#do sh ip route

D* 0.0.0.0/0 [90/3328] via 150.1.23.2, 00:00:08, GigabitEthernet0/1

https://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfeigrp.html


OSPF

OSPF does not have an auto summaization feature and can only perform summarization at specific points in the network. OSPF requires at an area has a the same database on each router in that area which means summarization can only be done at area borders.

There are 2 types of summarization

Area range – ABR, summarize internal routes as they get passed to another area as a type 3 interarea LSA

Summary address – ASBR, summarize external routes before injecting them into the OSPF domain at type 5 external LSA’s

https://supportforums.cisco.com/t5/network-infrastructure-documents/ospf-inter-area-route-summarization/ta-p/3145113

http://www.ciscopress.com/articles/article.asp?p=2294214&seqNum=3


BGP

BGP has multiple different ways to summarize routes

network w/ static route

Aggregate-address

R1(config-router)#do sh run | s bgp
router bgp 1
 bgp log-neighbor-changes
 network 1.1.1.1 mask 255.255.255.255
 aggregate-address 1.1.0.0 255.255.0.0
 neighbor 150.1.12.2 remote-as 2
R1(config-router)#

R2(config-router)#do sh ip route bgp
Codes: L - local, C - connected, S - static, 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
 i - IS-IS, su - IS-IS summary, 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, H - NHRP, l - LISP
 a - application route
 + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
B 1.1.0.0/16 [20/0] via 150.1.12.1, 00:00:03
B 1.1.1.1/32 [20/0] via 150.1.12.1, 00:00:03
R2(config-router)#
R2(config-router)#

https://learningnetwork.cisco.com/docs/DOC-11817

https://learningnetwork.cisco.com/docs/DOC-11853

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.