CCNP - ENTERPRISE - Route Summarisation with RIPv2, EIGRP, OSPF, IS-IS, BGP

In this post I'm going set down the necessary steps to implement summarisation in each protocol.

RIPv2:
On the router running RIPv2 you apply the summary to the outgoing interface:
R1(config)#int s0/0
R1(config-if)#ip summary-address rip 10.0.0.0 255.252.0.0

EIGRP:
Firstly disable auto summarisation-
R1(config)#router eigrp 1
R1(config-router)#no auto-summary

Next apply your summary route to the OUT Bound interface -
R1(config)#int s0/0/0
R1(config-if)#ip summary-address eigrp 1 172.16.0.0 255.255.224.0 

Points - Configured on a per interface basis, Router creates a NULL0 entry as loop prevention (longest match rule works here so if there isn't a more specific route within the summary route the router will drop the packet), When the last specific route within the summary is removed the NULL0 entry is removed.

OSPF:
Summarisation is performed on the ABR and ASBR only.
ABR - Applied to routes from within one area and summarised in to another area
ASBR - External routes are redistributed INTO ospf from protocols such as RIPv2 or EIGRP

For Intra-area route summarisation, on the ABR do:
R1(config)#router ospf 1
R1(config-router)# area 1 range 192.168.64.0 255.255.224.0
  *Area number is the area you are summarising FROM
 *#sh ip route - will show a NULL0 route to help prevent routing loops
 * #sh ip ospf database - will show the summary route

For Inter-area route summarisation, on the ASBR do:
R4(config)#router ospf 1
R4(config-router)#summary address 192.168.64.0 255.255.224.0
 *Advertises a summary route for all routes within 192.168.64.0/19 subnet

Note - By default ABR's and ASBR's do not summarise routes.

IS-IS:
Summarisation to be done on a Level1/2 router, which injects level 1 routes in to level 2.
If summarisation is being implemented, ALL level1/2 routers in the area need to be configured for summarisation.
Otherwise if one router advertises a more specific route then the Level 2 router will direct all traffic to that one router (due to the Longest Match rule).


On the Level1/2 router do:
R5(config)#router isis
R5(config-router)#summary-address 192.168.0.0 255.255.0.0 level-2
 *You state which level router you are summarising in to (default is level-2).

BGP:
BGP will not advertise a summary route unless the route can be first located in the Routing Table. As a result you can't simply apply a summary in the BGP process as it won't exist in the RT and therefore will not be advertised.


To get round this you first add a static route for the summary point to NULL0 and then you apply your summary route in BGP.


To do this do:
R2(config)#ip route 192.168.0.0 255.255.0.0 NULL0
!
R2(config)#router bgp 100
R2(config-router)#network 192.168.0.0 mask 255.255.0.0