EIGRP manual summarization of external route with ip summary eigrp

[Steph1963]

Hi,

On the following diagram, I woulld like to know if it is possible to manually summarize subnet 192.1.2.0/26 and 192.1.2.64/26 on router 2 in case where there is only static routes for these route in the routing table (on router 2).

I have read in Cisco documentation that EIGRP will not auto-summarize external routes unless there is a component of the same major network that is an internal route. My question is about the possibility of summarizing these two subnets on router 2 if there is a static route showing where these subnets exists. Does router 2 absolutely needs an EIGRP route for one of these two subnets before summarizing it or does static route is good enough to manually summarize these routes unter the interface facing router one.

I am basically trying to understand if we can summarize a route under an interface without using the network command in the router bgp section. Does any route available in the routing table can be summarze or only EIGRP route can be summarize.

Question 2)

Also would like to know if a default route must be present in the routing table before using the ip summary-address eigrp 1 0.0.0.0 0.0.0.0. command

Thanks for your help

Stephane

[Nagendra Kumar Nainar]

Hi,

AFAIK, you can summarize both internal and external routes without any issues. Only thing is, once you summarize external prefix, they will be advertised as internal EIGRP routes.

Regarding your Q2, It is not required to have 0.0.0.0/0 entry in your routing table to have "ip summary-address eigrp 1 0.0.0.0 0.0.0.0". Basically, summary-address command is to summarize few more specific prefixes and advetise one less specific prefix. By configuring, "ip summary-address eigrp 1 0.0.0.0 0.0.0.0", you summarize all possible subnets and advertise only 0.0.0.0/0.

HTH,

Nagendra

[Steph1963]

Hi Nagendra,

This means that any static, RIP/OSPF/BGP route can be summarize with EIGRP with the ip summary eigrp command­?

Thanks for your help

Stephane

[Nagendra Kumar Nainar]

Hi,

Any prefixes redistributd into EIGRP (External) or originated from EIGRP (Internal) can be summarized.

HTH,

Nagendra

[Mohamed Sobair]

Stephane,

TO manually summarize in Eigrp, the component prefixes should be in the Eigrp topology table, So you cant summarize at router 2, because router 2 doesnt have those subnets in the Eigrp topology table.

HTH
Mohamed

[Dhavantharim]

Hi

It is not possible to summarize the 192.168.2.0 network in to EIGRP

if you want to do that you must redistribute the static route in to EIGRP.

may be this could help.

regards

dhanvanthari

[Scott Cannon]

Hi Stephane,

I'm not sure I properly understand where your EIGRP AS ends. If its on R2 the you'll have to put the mannually summarised static route (ie 192.168.2.0/25) on R2. Obviously it can then advertise this to R1 if you enable static redistribution on R2. If you put hte individual routes on R2 and redistribute them then R1 will create its on summarised route (as long as you have auto-summary enabled).

Rgds

Scott

[vinod.agrahari]

Dear All,

As per my understanding about it is as we can summarize all the subnet on router two if redistribution is configured between the two protocols (Static and EIGRP) in the two and three routers.

Correct me if I am wrong at any point of time and thank you all as this is helping me a lot.

Regards

Vinod Agrahari

[Mohamed Sobair]

Hi,

You are correct, In order for router two to summarize these routes, it has to be in the Eigrp Topolgy table, So eventually if its redistributed, then you can Summarize it twords router 1.

Regards,

Mohamed